[Haskell-cafe] Backward compatibility

[Adrian May]

Hi All,

Please don't interpret this as a rant: I'm just feeling a bit disappointed about probably having to give up on Haskell. 

Let's face it: this decision to change the default syntax in GHC7 means that right now Haskell looks about as stable as Ruby on Rails.

I just tried to use Flippi. It broke because of the syntax change so I tried WASH. I couldn't even install it because of the syntax change. I persisted for a while but gave up because getPackageId doesn't exist in any form at all anymore. This was only the install script: what would WASH itself have in store for me to get my brain around?

What are my choices here:

1) Revert to GHC6 or put pragmas and compiler switches everywhere, switch 2010 off globally with cabal or even make an alias of ghc: That means I'll gradually clash with people who decide ...

2) Convert all my code and a lot of other peoples' to the new syntax, thereby exacerbating the problem that ruled out 1.

Either way, we're looking at a long period during which a large portion of the libraries will be incompatible with the other portion, and nobody will know which style to write. I don't know if or when WASH or any other library will convert, or even if I'd prefer that to happen sooner or later, because that would depend on when other libraries do and how I'd worked around it in the meantime. Altogether that means I can't sensibly decide to rely on any library, so I can't use Haskell. I'll just have to go back to fumbling around in XSL, PHP and the like. Is Haskell 2010 really so much better that it justifies this?

I just saw that movie "The Words": the moral of the story is that you shouldn't try to change your mistakes.

...

Apparently it's not only 2010. I now find that buildng the Haskell Platform wants GHC 7.4.2, not 7.4.1 because of the line "import Prelude" (if I remember rightly,) and even when I follow the rules precisely I still get several different deprecation warnings. The prelude is not exactly obscure. If you deprecate that you've broken everything. Is it really impossible to keep such a basic mantra meaningful from one minor version to the next? Java was fond of deprecating things in the early days, but when they said "deprecated" they didn't mean "switched off", let alone that it would lead to a syntax error. They just meant "not trendy anymore."

It's a very common illusion to believe that the central thing in your life is also the central thing in everybody else's. That's why things like Norton take over your whole machine: those guys believe that the only reason you bought the computer was to fight viruses, because that's what most of the machines in their office were bought for.

There seems to be something similar going on in the way Haskellers are expected to update all their code whenever GHC decide to issue an update. But in reality we have jobs of our own. I'd like to choose Haskell over XSL because I think it'll enable me to write web sites more efficiently, not because I want to forget all about my job and savour the brilliance of the latest Haskell version. But in reality I'm just sitting here waiting for the Platform to compile just in case it's the Ubuntu package's fault, but I know it won't help. I'll just get other problems instead. Reality is that the whole ecosytem is in disarray because of this lack of respect for backward compatibility. At least Rails can plead that it's relatively new, but Haskell has been around for over 20 years.

I understand that progress has to be made, and it would be nice if people did just update all their code quickly so you could switch off old stuff and move on. But it's not hard to survey the code that's out there and see how much stuff you'd be breaking if you did. If it's not a lot, then switching it off to wake them up would be an acceptable compromise. But it looks to me as if a lot of very important stuff is still failing on the GHC from November 2010, so clearly things are going too fast. Adding new stuff is great, and sometimes the new stuff clashes with the old stuff. But how much of that deprecated stuff really *needed* to be switched off, and couldn't the new stuff have been designed so as not to force that?

In principle this is the best language on the planet, but with all these version gotchas I don't know that I can use it anymore. What a tragedy. I can't even think of a suggestion as to how Haskell should try to get out of this mess now.

Adrian.

[Byron Hale]

Hello, everyone,

I was just in the process of trying to get Haskell 7.6 installed.  First I surveyed all the current OSes that seemed to support it.  FreeBSD 9.1 seemed like a good candidate.  However, FreeBSD 9.1 has many practical problems of its own.  So far, I have 7.4 installed, but not 7.6.  Would the MAC be better at this?  Anyway,  it seems that much of Hackage will not be usable.  Perhaps I should just run it on Windows, as it seems likely to install there and much of Hackage already didn't work there.

I welcome any constructive suggestions.

Best Regards,

Byron Hale

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[Johannes Waldmann]

Adrian May <adrian.alexander.may <at> gmail.com> writes:

> this decision to change the default syntax in GHC7

what decision? what syntax? here's the release notes (7 vs. 6)
http://www.haskell.org/ghc/docs/7.0.1/html/users_guide/release-7-0-1.html

I guess you are referring to hierarchical module names?
(import List => import Data.List)

Indeed, I cannot build
WASH http://hackage.haskell.org/package/WashNGo-2.12.0.1
on ghc-7.6.3, and I don't see how it could have worked on 7.0,
as hackage claims it did.

(building the executables:
when using base and haskell89, "import Prelude" is ambiguous;
when using haskell98 only, modules like System.Exit are not available.)

I think this could be fixed in a straightforward way,
but that "fixing it" is necessary at all, just proves your point.

- J.W.

[Johannes Waldmann]

Byron Hale <byron.hale <at> einfo.com> writes:

> I was just in the process of trying to get Haskell 7.6 installed.

You cannot "install Haskell 7.6". Haskell is a language.

You can install a language implementation (compiler/interpreter).
There may be several. You can also install a set of libraries.
These may be bundled (one compiler with one set of libraries).
One such bundle is called "the Haskell platform".
Is this what you are trying to install? (But then the version is nothing
like 7.6, this looks more like a compiler version.)

Of course this naming error is directly suggested by haskell.org, where
we have the equally meaningless "Download Haskell" right on the front page.

- J.W.

[Ertugrul Söylemez]

Adrian May <adrian.ale...@gmail.com> wrote:

> Please don't interpret this as a rant: I'm just feeling a bit
> disappointed about probably having to give up on Haskell.
>

> [rant that update broke stuff]

Well, it is a rant, so you can just as well concede it. =)

The Haskell community and its descendants (Agda, Disciple, Idris, ...)
differ from all other developer communities I know in one point: We
don't fear change. There is a reason why other communities do:
Non-downward-compatible changes will break stuff. We are aware of that.

Occasionally things will break, when they worked perfectly before an
update. Does that mean that Haskell sucks? Not really. It means that
some library developers will have to get rid of their old bad habits.
This is unlikely to happen for unmaintained projects like WASH. So the
question you should be asking yourself is: Do you really want to use
WASH? I'm surprised that you could build it with any GHC 7.x at all.

If you don't like this experimentalism and the rigor with which we get
rid of old problems (which isn't even that rigorous -- Functor and Monad
are still independent classes even today), then Haskell may indeed be
the wrong choice for you. However, you should always ask yourself: Who
is the one with bad habits?

Consider PHP: It was broken since the beginning and is still broken
today. The developers carefully make sure that it stays broken, because
fixing it would break applications. They don't want them to break.
That means that you can rely on all of your old bad habits, keep your
SQL injection vulnerabilities, your broken program logic, etc. Is this
good or bad?

Consider Debian, the PHP of Linux distributions: Their philosophy is
never to touch a running system, so instead of employing architectural
changes they keep the old code bases as long as possible and follow a
rigorous backporting policy. They don't want you to have to rewrite
your configuration files or update your shell scripts or whatever
at-most-five-minutes steps would usually be necessary after an update.
It should Just Work. Is this good or bad?

To express this question in a broader context: Are you leaving a broken
tool and replacing it with a new shiny one? Or are you really just
replacing a small problem by a big one? Haskell's change policy is a
small problem that prevents you from big problems. PHP is a big problem
all by itself. Do you really want to leave this wonderful realm just
because of one setback? Keep in mind that this setback is an integral
part of why Haskell shines where PHP sucks.

Think about it. ;)

> In principle this is the best language on the planet, but with all
> these version gotchas I don't know that I can use it anymore. What a
> tragedy. I can't even think of a suggestion as to how Haskell should
> try to get out of this mess now.

We all have to deal with these gotchas. However, I'm still much more
productive with Haskell than with any other language. When I go to a
new GHC major version I always expect some old packages to fail, and I'm
often surprised by the small number of packages that actually do.

So my closing comment is: Haskell is one of the best languages, but
that greatness comes at a price. Deal with it. Going back to PHP is
not the answer.

Instead you should recognize that now is the time to look into one of
the big three web frameworks of today: Happstack, Snap and Yesod. The
tool that is broken and needs to be replaced is WASH, not Haskell.


Greets,
Ertugrul

--
Not to be or to be and (not to be or to be and (not to be or to be and
(not to be or to be and ... that is the list monad.

[Adrian May]

Hi Ertugrul,

> Well, it is a rant, so you can just as well concede it. =)

By my standards that was a lullaby ;-)

Everything you said is correct. Just like everything I said. 

The best policy lies between the two extremes. Your extreme would be fine if Haskell presented itself as a purely theoretical research tool. But it actually wants people to use it for stuff that peoples' livelihoods depend on. 

So there are some shiny new frameworks out there which unlike WASH didn't break yet. Thanks for the pointers. I tripped over blaze a moment ago (so no I didn't stomp back to PHP after all) which mentions something called Snap. I'll check out your other suggestions too. 

But what about two years from now? Will they still be working by then or will their developers have got just as sick of continually moving goalposts as those of WASH evidently did? Or would I be taking on the job of maintaining it myself? I guess you'll be telling me that Happstack is a bad habit of mine and I should rewrite my whole system in whatever the new thing is by then.

I mentioned this trade-off that you talk about towards the end of my rantaby. It's true that we can't have the best of both worlds but perhaps a little restraint would be appropriate. I mean, are you saying that Haskell was really bad when it could make up its mind what "import Prelude" meant? If you really want to change something that basic, how about calling the new one Prelude2? I kinda liked Haskell even in 1998. I just don't see why switching new things on has to mean switching old things off. You can't have your cake and eat it, but I see no reason to shit all over one half of the cake just because you're more interested in the other half.

Also, there's no real value in blaming these problems on the maintainers for retaining the "bad habits" that they learned from Haskell. The reality is that the forums are crammed with people suffering this kind of thing. It doesn't make a difference who you blame. Either way, the ecosystem looks untrustworthy, so fewer people will adopt it, and it'll be retreating from its original stated goal, which IIRC was to be a standard and widely used FL. It might be very rigorous and clever, but that's not much use if it's only being used by the people who have a full time job making it even cleverer. 

Not a lot of people in industry are using Haskell. More are using Erlang, Ocaml, XSL, J#, etc so it can't be just because they're scared of FP. If you'd rather see more using Haskell, I strongly suggest you get a grip on what real companies actually have to worry about. It ain't mathematical rigour. Backward compatibility is a big chunk of it.

Adrian.

[Alexander V Vershilov]

Hello.

On 2 May 2013 14:33, Adrian May <adrian.ale...@gmail.com> wrote:

Hi Ertugrul,

> Well, it is a rant, so you can just as well concede it. =)

By my standards that was a lullaby ;-)

Everything you said is correct. Just like everything I said. 

The best policy lies between the two extremes. Your extreme would be fine if Haskell presented itself as a purely theoretical research tool. But it actually wants people to use it for stuff that peoples' livelihoods depend on. 

There are 2 extremes: 1). [enterprise extream] do thing once - let it work forever without changes, 2). [developer extreme] - change your applications in a continuous way. Both extremes are not right: first hides a problem, and when a problem got revealed everything is so terribly broken that you
need to start from the begining, second extreme require work on things as soon as environment changes (dependencies updates, libraries changes, bugs revealed and fixed). The correct way is scheduled upgrade and Haskell in very close to it. If you see a bug or missfieature or improvement, and it's better - deprecate old, and do changes, then give a time gap for others to fix. That is a really good way, if you have to do changes it means that
smth have not done right. As for WASH it has extremely long gap to be fixed, and it simply should be fixed without any philosophical letters to ML.

So there are some shiny new frameworks out there which unlike WASH didn't break yet. Thanks for the pointers. I tripped over blaze a moment ago (so no I didn't stomp back to PHP after all) which mentions something called Snap. I'll check out your other suggestions too. 

But what about two years from now? Will they still be working by then or will their developers have got just as sick of continually moving goalposts as those of WASH evidently did? Or would I be taking on the job of maintaining it myself? I guess you'll be telling me that Happstack is a bad habit of mine and I should rewrite my whole system in whatever the new thing is by then.

I mentioned this trade-off that you talk about towards the end of my rantaby. It's true that we can't have the best of both worlds but perhaps a little restraint would be appropriate. I mean, are you saying that Haskell was really bad when it could make up its mind what "import Prelude" meant? If you really want to change something that basic, how about calling the new one Prelude2? I kinda liked Haskell even in 1998. I just don't see why switching new things on has to mean switching old things off. You can't have your cake and eat it, but I see no reason to shit all over one half of the cake just because you're more interested in the other half.

Also, there's no real value in blaming these problems on the maintainers for retaining the "bad habits" that they learned from Haskell. The reality is that the forums are crammed with people suffering this kind of thing. It doesn't make a difference who you blame. Either way, the ecosystem looks untrustworthy, so fewer people will adopt it, and it'll be retreating from its original stated goal, which IIRC was to be a standard and widely used FL. It might be very rigorous and clever, but that's not much use if it's only being used by the people who have a full time job making it even cleverer. 

 

At least in Gentoo you can just use a wrapper for haskell packages there are ~600-700 pkgs like in debian but with difference that they can be built on ghc-6.1(not everytime), 7.4, 7.6, and some on HEAD, and we use frontline versions (latest available+some more for quickly changing packages) is used. All packages are patched accordingly if compatibility between them is broken and we tries to send patches upstream.

Not a lot of people in industry are using Haskell. More are using Erlang, Ocaml, XSL, J#, etc so it can't be just because they're scared of FP. If you'd rather see more using Haskell, I strongly suggest you get a grip on what real companies actually have to worry about. It ain't mathematical rigour. Backward compatibility is a big chunk of it.

Adrian.

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[John Lato]

On Thu, May 2, 2013 at 5:30 PM, Ertugrul Söylemez <e...@ertes.de> wrote:

 

To express this question in a broader context:  Are you leaving a broken
tool and replacing it with a new shiny one?

So I read the original post, and it really wasn't clear to me what exact changes were causing the issues; I don't think I'm alone in thinking the OP could have been a bit more explicit about the nature of the problem.  Also, at least Flippa is explicitly unmaintained (according to the first hit googling "Flippa Haskell"), and I hadn't seen mention of WASH for a year or more.  And of course, ghc-7.0 was released 2.5 years ago, ghc-7.6 is the current version, and there's been ample time for incompatibilities to accumulate.

Despite those issues I'm rather sympathetic to the OP, in part because most of these "breaking changes" aren't replacing a broken tool.  If the Functor/Applicative/Monad hierarchy were fixed it would cause a lot of breakage, and I (like many of us I'm sure) would have to update a lot of packages, but I wouldn't mind because that would be a clear improvement.  But replacing "import List" with "import Data.List"?  That's not even a problem.  Consider another breaking change, requiring newtype constructors be in scope for foreign imports.  This required a lot of code churn, especially as IIRC the CDouble constructor wasn't exported previously (for reasons of "abstraction", which I can also rant about), so of course it wouldn't have been in explicit import lists.  At least this has some marginal utility if you care about Safe Haskell.

I did a lot of work to get packages compilable with ghc-7.6 and submitted patches to probably a dozen different repos.  Aside from one exception (related to the FFI), every breaking change was either related to namespacing/import issues, or bumping versions in .cabal files (I consider the whole try/catch mess to be an import issue, although at least in that case the benefit is more obvious).  Two pragmas existed that duplicate functionality, one was deprecated in the last release and now the other one is deprecated while the first has been un-deprecated.  It's just rearranging deck chairs.  It doesn't feel like a significant improvement, and it's even harder to bill as one.

I don't think there's anything wrong with moving at a fast pace, nor do I think backwards compatibility should be maintained in perpetuity.  Unfortunately this leaves a lot of scope for migrations to be handled poorly, and for unintended consequences of shiny new systems.  IMHO both have caused issues for Haskell developers and users in the recent and more distant past.  This is an issue where I think the community should continually try to improve, and if a user calls out a difficulty we should at least try to learn from it and not repeat the same mistake.

(Unfortunately I'm not really sure what we can learn from this particular case, but maybe somebody wiser than me could point the way)

[Ertugrul Söylemez]

Adrian May <adrian.ale...@gmail.com> wrote:

> [...] If you'd rather see more using Haskell, I strongly suggest you

> get a grip on what real companies actually have to worry about. It
> ain't mathematical rigour. Backward compatibility is a big chunk of
> it.

I'm not saying that you are wrong, but you may be looking at it from the
wrong angle: Unmaintained projects depending on one of the major web
frameworks still compile today. The strong version constraints used by
packages and taught by the package versioning policy makes this
possible. When you install it, it does the right thing.

WASH on the other hand is really a legacy from the stone age of real
world development in Haskell. As said, I'm surprised that you could
even compile it today. I consider it a proof of concept that web
application development is very possible with Haskell and the community
has moved on to implement real web frameworks made for production use.

This happens for all languages, not only Haskell. You may find that one
or the other C/C++ package breaks with GCC 4 when it compiled just fine
with GCC 2. This is why we have the major/minor/patch-level split in
the first place. You can't expect that nothing will break when you
update from GCC 3 to GCC 4. The same holds for GHC and even for
strongly keep-being-retarded language implementations like PHP.

At some (quite recent) point in time the whole language was revised and
is called Haskell 2010 now. You can still compile with Haskell 98 and
many old packages should still work, unless they are broken by the new
base library. With the new language it's simply that the type system
has changed in an incompatible way. It's not that features have been
removed, but simply that you have to express them differently now. This
is most noticable for local bindings, but you will also find that the
base library has undergone some breaking changes. This was the most
legacy-breaking change I can remember, but it was necessary. We all
suffered from bad decisions made in the old days. This is also likely
the change that broke WASH.

Other than this the Haskell ecosystem is actually comparatively stable.
It is so stable that actually we run into another problem, which we
refer to as the Cabal Dependency Hell. Semisolutions like cabal-dev are
available, but we really need to do some work here. This is probably
the weakest part of the Haskell ecosystem right now. However, it's also
actually a very hard problem. Other languages have the same problem,
but they fix it by ignoring it. Programmers in those languages just
pretend that it's impossible to install multiple versions of the same
package, but if operating systems like NixOS gain more popularity they
will have to reconsider their philosophy when they face sudden
segfaults. Haskell's Cabal would have warned them. They don't have
such a tool.

In other words, you are likely suffering from the one big breaking
change made in Haskell's modern history (i.e. post 1998). Don't be
discouraged by that and enjoy the improved language and base library.
Enjoy an ecosystem that acknowledges the existence of problems and the
tools you get to find a solution that fits you. You are going into the
right direction now. =)

[Ertugrul Söylemez]

John Lato <jwl...@gmail.com> wrote:

> I don't think there's anything wrong with moving at a fast pace, nor
> do I think backwards compatibility should be maintained in perpetuity.

I think this statement pretty much covers the mindset of the Haskell
community and also explains the higher breakage rate of Haskell packages
when compared to other languages, in particular non-static ones: We
move at a very fast pace. Innovations are made all the time. Without
this feature we wouldn't be where we are today.

Of course Haskell, being a rigorously static and correct language and a
community that equally rigorously insists on correctness of design
patterns we have to live with the fact that we need to fix the breakages
we introduce, and we do that. This is a good thing.

> Unfortunately this leaves a lot of scope for migrations to be handled
> poorly, and for unintended consequences of shiny new systems. IMHO
> both have caused issues for Haskell developers and users in the recent
> and more distant past. This is an issue where I think the community
> should continually try to improve, and if a user calls out a
> difficulty we should at least try to learn from it and not repeat the
> same mistake.

I think we do that. The most severe breakages are introduced by new GHC
versions. That's why there is the Haskell Platform. If users decide to
move to new versions sooner they should be prepared to handle the
breakages. In particular a Haskell beginner simply shouldn't use
GHC-HEAD. Our type system makes us aware of the breakages we introduce
and gives us the opportunity to fix them properly before exposing them
to the users.

With this in mind I don't think there is anything to learn from this
particular case. You wouldn't use WASH today for the same reasons you
wouldn't use Linux 0.x. It's a legacy, and the ideas from it have
inspired the more recent web frameworks, which are more convenient,
faster, more real-world-oriented. In fact I totally expect a new
generation of web frameworks to pop up in the future, more categorical,
even more convenient and less error-prone.


Greets,
Ertugrul

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[Brandon Allbery]

On Thu, May 2, 2013 at 1:27 AM, Adrian May <adrian.ale...@gmail.com> wrote:

Let's face it: this decision to change the default syntax in GHC7 means that right now Haskell looks about as stable as Ruby on Rails.

I just tried to use Flippi. It broke because of the syntax change so I tried WASH. I couldn't even install it because of the syntax change. I persisted for a while but gave up because getPackageId doesn't exist in any form at all anymore. This was only the install script: what would WASH itself have in store for me to get my brain around?

I'm going to give you the flip side of this one.

I've been active in the Perl community (admittedly in something of an off and on fashion for health reasons) for years. Perl 5 is in some ways the epitome of "maintain backward compatibility": there is a lot of Perl code out there that was written under Perl 4 or earlier. (cpanel, I'm looking at you. Among others. I recently got to debug some code related to someone's RADIUS server that looked like it hadn't been touched since perl3.)

And this is the direct cause of the Perl ecosystem being a sewer. Nobody is willing to take the step of making Perl default to the eminently sane behavior of checking for invalid inputs, because it will "break" too much existing (already horribly broken, in reality) code. Nobody will risk disabling the walking security hole and encouragement of sloppy, buggy code that is Perl's 2-argument open(). (If you ever wondered why Perl 6 decided to throw out source compatibility, here's your reason.)

The Haskell98 ecosystem wasn't nearly that bad, but maintaining compatibility with it did prevent fixing various flaws in things like exception handling. Between the two, I'd rather see older code broken in the name of current code actually working correctly. And in Haskell I get a lot of help from the compiler to bring that older code up to date.

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unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net

[Adrian May]

So WASH is ancient history. OK, lets forget it.

How about the Haskell Platform? Is that ancient history? Certainly not: it doesn't compile on anything but the very newest GHC. Not 7.4.1 but 7.4.2. Now that's rapid maintenance, but it's still version hell because you've got to have that compiler installed first (even though HP is supposed to be a way to acquire haskell) and you probably haven't. You've probably got the one from the linux package which hasn't been maintained since, ooh, must have been at least a week ago, so you install the new one and you've trashed cabal. How long is that puzzle gonna take to unravel? That's how I spent my afternoon today, instead of getting on with my job. Now you might think I was silly not to have uninstalled the linux package first, but I tried, and then decided against it because it thought the entire OS depended on it and actually proposed to remove everything from clib to googleearth as a solution. It's not Haskell's fault that linux package management is as broken as any other for the same reasons, but in an imperfect world, it's better not to keep moving the furniture around. 

Why was I trying to build the Haskell Platform at all? Because it wasn't obvious to me that a 7 year old library would be doomed. I find it perfectly normal to be able to compile C code from the 1970s but still run STL through the same compiler. That's why I blamed the system instead of the library. And unless somebody can explain to me how I would rescue my business now if I had opted for WASH in that long-forgotten era when Barack Obama was barely known, a Russian spy was poisoned with Polonium and a Sudanese man was ordered to marry a goat he was caught in an intimate position with, then I still see it that way.

Adrian.

 

[David Thomas]

If you are actively using something then keep it up to date, encourage someone to keep it up to date, pay someone to keep it up to date, or migrate off of it.  If you try building with a fresh set of packages every so often, you can catch breaking changes early and deal with them when it's typically pretty clear why things broke.

[Tom Ellis]

On Thu, May 02, 2013 at 09:26:15PM +0800, Adrian May wrote:
> How about the Haskell Platform? Is that ancient history? Certainly not: it
> doesn't compile on anything but the very newest GHC. Not 7.4.1 but 7.4.2.

I'm uninformed in such matters, but from

http://www.haskell.org/platform/changelog.html

it looks like GHC 7.4.2 is *part* of Haskell Platform 2012.4.0.0, so it
doesn't make sense to talk about the latest Platform without 7.4.2.

I know that sounds like a technicality, but I don't think it actually is!
The important question is whether *your* old code breaks with the latest
Platform, not whether the latest Platform breaks with GHC 7.4.1.

Tom

[Mark Lentczner]

On Thu, May 2, 2013 at 6:26 AM, Adrian May <adrian.ale...@gmail.com> wrote:

How about the Haskell Platform? Is that ancient history? Certainly not: it doesn't compile on anything but the very newest GHC. 

I think you're missing the point of the platform! It is an explicit set of versions, including GHC, that make a stable reference set of packages on which to build, test, and deploy. Each version of the platform explicitly states with equality constraints the exact version of each component so that it will be the same for everyone.

You use the HP - with the GHC it comes with (or specifies) - as a set. You want to use GHC 7.4.1? Use HP 2012.2.0.0. Once installed you can install newer versions of the component packages if needed (though cabal-dev or cabal sandboxing is strongly encouraged in such a case to avoid "cabal hell".)

And unless somebody can explain to me how I would rescue my business now if I had opted for WASH

By patching it. Surely we are talking about minor changes here.

- Mark 

[Adrian May]

If you are actively using something then keep it up to date, encourage someone to keep it up to date, pay someone to keep it up to date, or migrate off of it.  If you try building with a fresh set of packages every so often, you can catch breaking changes early and deal with them when it's typically pretty clear why things broke.

Not necessarily. Let's take Flippi as an example. What seems to be happening there is that Text.Html is incompatible with CGI.Html, or something like that. Those are both vanilla modules that would not be under my control. If somebody else decides to make them incompatible, there's nothing I can do. Not without a total rewrite, but by then I might have 20 man-years invested in it. Nobody is gonna do a big project in a language with this attitude.

What if Android were written in Haskell for instance. At the famous 10:1 ratio there'd be roughly 5 million lines of it. "Nice update guys - we only had to rewrite 100,000 lines this time." Then you'd be afraid of change cos it would be your own phone you were breaking. 

[Adrian May]

I think you're missing the point of the platform! 

I suppose I did miss the point of the platform: I was trying to build it, which requires at least part of the platform. As I say, the reason I was trying to build it was that I wrongly blamed the ubuntu package for WASH not working. But that was not dumb unless you consider it obvious that 7 year old code would be broken, in which case it would be obvious that nobody would trust this language in production.

> > And unless somebody can explain to me how I would rescue my business now if I had opted for WASH

> By patching it. Surely we are talking about minor changes here.

Yeah but how many minor changes? This trigger-happiness is rife. 

And that's the first time anybody suggested the necessary changes to WASH should be minor. Everybody else thinks I was nuts to expect anything from 7 year old code. I don't know because I couldn't get past the install. Somebody had deleted getPackageId.

Please would somebody explain to me what getPackageId did to incriminate itself? I'm sure there's something much groovier now, like getting it inside a monad in case it changes during the installation itself (pretty likely AFAICT) but it's really just a package id. Can we honestly philosophise about the mathematical rigour of getPackageId? 

It was needlessly assassinated. For all I know WASH might be just fine apart from that, and maybe I would have liked it, even if it is from the dark ages. 

Yes there are times when something has to change. I acknowledged that in my original post. But I see no evidence whatsoever that anybody in control of Haskell is holding fire even on things as innocent as getPackageId or as ubiquitous as the prelude. I'm not asking for the opposite extreme of conservatism, just a bit of common sense instead of this bloodbath. 

[Brandon Allbery]

On Thu, May 2, 2013 at 10:36 AM, Adrian May <adrian.ale...@gmail.com> wrote:

I think you're missing the point of the platform! 

I suppose I did miss the point of the platform: I was trying to build it, which requires at least part of the

Having to build it already indicates that something is wrong, unless you're porting to an unsupported OS/hardware.

 

platform. As I say, the reason I was trying to build it was that I wrongly blamed the ubuntu package for

That said, may I point out that the Ubuntu packages *are* broken? They shipped a mangled Platform which can't be relied on for much; instead of a well-tested set of packages, they took a good Platform and replaced bits with minimal testing. Yes, this has actually caused problems for people.

Yes there are times when something has to change. I acknowledged that in my original post. But I see no evidence whatsoever that anybody in control of Haskell is holding fire even on things as innocent as getPackageId or as ubiquitous as the prelude. I'm not asking for the opposite extreme of conservatism, just a bit of common sense instead of this bloodbath. 

You're assuming here that someone deliberately targeted your favorite pet. I don't know the details but I VERY STRONGLY doubt anyone said "oh, we should break that function". But I ALSO find it likely that it was the victim of something sufficiently pervasive that the options were "break it" or "live with something else being broken forever, just like Perl vs. cpanel!"

This, sadly, is the real world. The holy grail of fixing bugs without breaking any program ever anywhere is impossible, and even "fix this bug without breaking many other programs" is extremely unlikely. Your choices are this, or Perl/PHP "we do not dare fix bugs or misdesigns because someone's pet program will die".

(Other examples of this:

- Python 3. Note how many existing Python packages still require Python 2.

- The C and C++ standards are increasingly Byzantine due in large part to backward compatibility issues; but I'm guessing from your complaints that this is your ideal model because "old programs still work". Lucky you, you can happily pretend that it's because they have found some magical way to do the fundamentally impossible --- right up until reality bites back.

)

-- 

[Mark Lentczner]

On Thu, May 2, 2013 at 7:36 AM, Adrian May <adrian.ale...@gmail.com> wrote:

I suppose I did miss the point of the platform: I was trying to build it, which requires at least part of the platform.

This is not for the faint of heart. Like *ALL* language distributions I know (C++ included), boot-strapping the next rev is never easy. Consider building the stdc and stl for version gcc x with gcc x-1 - Or trying to assemble and test packages for python 2.x with only python 2.(x-1)

 just a bit of common sense instead of this bloodbath. 

Now you're being hysterical. The changes don't rise to that level at all. Vast swaths of haskell code have continued to work just fine over the last many years of changes. And many more have continued to work with only minimal maintenance.

The changes over the last several years are no more extreme than I see in other systems. Consider that Mac OS X ships with Python2.5 and 2.6 and 2.7 all installed because of incompatibilities in the base set of libraries.

If you are comparing it C++ library stability you are being myopic: The situation in C++ system libraries was so complex that it spurred the monster that is autoconf! That the most common libs have settled into a very stable set that can be expected to work over several years and major releases, has only been true in the last decade. The prior three decades of C (and later C++) were filled with tons of this sort of versioning difficulty, compounded by multiple systems.

- Mark

[Tom Ellis]

On Thu, May 02, 2013 at 10:36:18PM +0800, Adrian May wrote:
> Please would somebody explain to me what getPackageId did to incriminate
> itself?

What's getPackageId? It does not appear in the WASH source.

Tom

[Adrian May]

What's getPackageId?  It does not appear in the WASH source.

It's in Setup.lhs, in WashNGo.

[Tom Ellis]

On Thu, May 02, 2013 at 11:10:33PM +0800, Adrian May wrote:
> > What's getPackageId? It does not appear in the WASH source.
>
> It's in Setup.lhs, in WashNGo.

Which source of WashNGo are you using? It doesn't appear in either of these
versions:

http://hackage.haskell.org/package/WashNGo-2.12
http://hackage.haskell.org/package/WashNGo-2.12.0.1

[Adrian May]

Which source of WashNGo are you using?  It doesn't appear in either of these
versions:

    http://hackage.haskell.org/package/WashNGo-2.12
    http://hackage.haskell.org/package/WashNGo-2.12.0.1

http://www.informatik.uni-freiburg.de/~thiemann/WASH/WashNGo-2.12.tgz

[Tom Ellis]

On Thu, May 02, 2013 at 11:23:12PM +0800, Adrian May wrote:
> > Which source of WashNGo are you using? It doesn't appear in either of
> > these
> > versions:
> >
> > http://hackage.haskell.org/package/WashNGo-2.12
> > http://hackage.haskell.org/package/WashNGo-2.12.0.1
>
> http://www.informatik.uni-freiburg.de/~thiemann/WASH/WashNGo-2.12.tgz

I get a 403 FORBIDDEN on that. How did you get it?

[Ivan Lazar Miljenovic]

On 3 May 2013 01:04, Brandon Allbery <allb...@gmail.com> wrote:
> On Thu, May 2, 2013 at 10:36 AM, Adrian May <adrian.ale...@gmail.com>
> wrote:
>>>
>>> I think you're missing the point of the platform!
>>
>>
>> I suppose I did miss the point of the platform: I was trying to build it,
>> which requires at least part of the
>
> Having to build it already indicates that something is wrong, unless you're
> porting to an unsupported OS/hardware.

Or you have a source-based distro, or you prefer building it yourself
rather than using distro packages (as they might be out of date or
b0rked), etc. ... ;-)

--
Ivan Lazar Miljenovic
Ivan.Mi...@gmail.com
http://IvanMiljenovic.wordpress.com

[Adrian May]

I get a 403 FORBIDDEN on that.  How did you get it?

 

I guess you just gotta know the right people ;-)

I attached the tarball. Don't say you got it from me, OK.

[Ertugrul Söylemez]

Adrian May <adrian.ale...@gmail.com> wrote:

> I attached the tarball. Don't say you got it from me, OK.

That's a weird thing to demand in a public mailing list with public
search-engine-locatable archives. =)

[Tom Ellis]

That tarball still doesn't contain the string "getPackageId".

You're complaining that you can't build a package, which hasn't been
maintained for several years, which you got from a secret source, and whose
whose Hackage page specifically says it doesn't build beyond GHC 7.0. I
don't think this is indicative of a serious failure of Haskell.

Tom

[Stephen Tetley]

Hi Adrian

I don't want to argue against your rant for the sake of it, but
Haskell is a fairly conservative language. The Glasgow Haskell
Compiler supports it's own dialect "Glasgow Haskell" which is fast
moving, but the developers of GHC do work hard to maintain
compatibility with standard Haskell 98 and Haskell 2010 (optionally
enabled with compiler flags). Afterall Haskell now is fairly widely
used as a teaching language which befits stability as course
textbooks, lecture plans etc. can't be in hock to a language that
changes every year.

Best wishes

Stephen

[Patrick Wheeler]

@Adrian May if you want that much backward compatibility you probably need to move to an operating system that suports it.

NixOS, already mentioned by another commentator,  would be my recommendation if you really need the backward compatibility  I just finished compiling both Flippi and WashNGo with ghc-7.0.4.

I do not want the GHC maintainers to be tied down by maintenance concerns any more then they already are, there time is more productively spent on concerns other then increasing backward compatibility.

For anyone who works on GHC thank you for helping support such a great ecosystem that enables this level of experimentation and rate of new features.

Patrick Wheeler

--
Patrick Wheeler
Patrick.Jo...@gmail.com
Patrick....@rice.edu
Patrick...@colorado.edu

[Adrian May]

I'm sorry: it was showPackageId. And the tarball came from this page: http://www.informatik.uni-freiburg.de/~thiemann/WASH/ which certainly isn't secret to Gooliath: I got it by searching for "haskell cgi html". I don't know why you can't download it.

Anyway, I've noted your opinions but today I really need to get something done. Thanks for the discussion.

Adrian.

[Alexander Solla]

On Thu, May 2, 2013 at 6:26 AM, Adrian May <adrian.ale...@gmail.com> wrote:

So WASH is ancient history. OK, lets forget it.

How about the Haskell Platform? Is that ancient history? Certainly not: it doesn't compile on anything but the very newest GHC. Not 7.4.1 but 7.4.2.

GHC is up to 7.6.

 

Now that's rapid maintenance, but it's still version hell because you've got to have that compiler installed first (even though HP is supposed to be a way to acquire haskell) and you probably haven't. You've probably got the one from the linux package which hasn't been maintained since, ooh, must have been at least a week ago, so you install the new one and you've trashed cabal. How long is that puzzle gonna take to unravel?

About 12 seconds, if you read http://www.haskell.org/platform/linux.html:

Download the source tarball for Unix-like systems: here

•  haskell-platform-2012.4.0.0.tar.gz 
• SHA-1: 7976508c50305969f64c721a1d095ae22efff8b7

Get and install GHC 7.4.2 prior to building the platform:

• GHC 7.4.2

Finally, unpack the Haskell Platform source tarball, and run (possibly with 'sudo'):

    ./configure

    make

    make install




[Carter Schonwald]

Emphatic agreement on this point. 

Likewise, the strong type system and the often helpful type error messages make it really easy to update code to work with more modern libs!

-Carter

[Alexander Solla]

 

Now that's rapid maintenance, but it's still version hell because you've got to have that compiler installed first (even though HP is supposed to be a way to acquire haskell) and you probably haven't. You've probably got the one from the linux package which hasn't been maintained since, ooh, must have been at least a week ago, so you install the new one and you've trashed cabal. How long is that puzzle gonna take to unravel?

About 12 seconds, if you read http://www.haskell.org/platform/linux.html:

Download the source tarball for Unix-like systems: here

•  haskell-platform-2012.4.0.0.tar.gz 
• SHA-1: 7976508c50305969f64c721a1d095ae22efff8b7

Get and install GHC 7.4.2 prior to building the platform:

• GHC 7.4.2

Finally, unpack the Haskell Platform source tarball, and run (possibly with 'sudo'):

    ./configure

    make

    make install

Also, the Haskell Platform ./configure step checks which version of GHC you have installed, and requires you to pass the option --enable-unsupported-ghc-version in order to compile it with anything other than GHC 7.4.2.

Did you try an unsupported version?  And now you're complaining? 

[Adrian May]

Also, the Haskell Platform ./configure step checks which version of GHC you have installed, and requires you to pass the option --enable-unsupported-ghc-version in order to compile it with anything other than GHC 7.4.2.

Did you try an unsupported version?  And now you're complaining? 

This is getting into minutia now, but yes I tried the unsupported flag and as I already explained it barfed about the prelude. So I installed 7.4.2 from source but that confused cabal because my attempt to uninstall the ubuntu package with 7.4.1 in had failed with dependency-hell. Figuring out why (or even that) my packages weren't being seen was the puzzle I was referring to. The point is that we wouldn't have to be talking about this at all if people didn't move the furniture around all the time. 

> Likewise, the strong type system and the often helpful type error messages 

> make it really easy to update code to work with more modern libs!

I'm also a big fan of the error messages, but it's nice to know if I caused them or somebody else did.

[Alexander Solla]

On Thu, May 2, 2013 at 8:43 PM, Adrian May <adrian.ale...@gmail.com> wrote:

Also, the Haskell Platform ./configure step checks which version of GHC you have installed, and requires you to pass the option --enable-unsupported-ghc-version in order to compile it with anything other than GHC 7.4.2.

Did you try an unsupported version?  And now you're complaining? 

This is getting into minutia now, but yes I tried the unsupported flag and as I already explained it barfed about the prelude.

How is it minutia that you expect an unsupported version of GHC to work?

Yes, I try it out sometimes.  And if it works, great.  If not, too bad, I'll wait until the next Haskell Platform.  I don't whine about it in public.

 

So I installed 7.4.2 from source but that confused cabal because my attempt to uninstall the ubuntu package with 7.4.1 in had failed with dependency-hell. Figuring out why (or even that) my packages weren't being seen was the puzzle I was referring to.

So the complaint is about Ubuntu?

 

The point is that we wouldn't have to be talking about this at all if people didn't move the furniture around all the time. 

That's not a very good point. It sounds as though you're the one who moved furniture around, considering that you managed to mix up Ubuntu's GHC package with your hand-built ones.

[Adrian May]

Yes, I try it out sometimes.  And if it works, great.  If not, too bad, I'll wait until the next Haskell Platform.  I don't whine about it in public.

May I venture a guess that you never tried to manage a 5-10 million line project?

That's what I do. I'm not a programmer, I'm a manager. I run teams of a few dozen people on subprojects within huge telecom-related projects, and my job is to try and keep it all from collapsing in a heap of bugs. 

If you had any experience of that you'd run a mile from any technology with this hit and miss attitude. I can't tell people what version they should be using because half of them work for a completely different company. They have their own dependencies coming from other projects that I'm not even allowed to know about. One of the ways I keep codebases alive is by telling people not to assume that somebody else is following the instructions in their heads. If anybody in my team wants to assume anything about the versions of anything they interact with, they'll need a very good argument as to why they can't make their bit more flexible. But I never had to be scared of upgrading any compiler, except python that is.

Is anybody in the Haskell community still interested in attracting new users? If so I suggest you go play with Ruby on Rails. Then you'll know what it's like to approach a complex and unfamiliar system where every crumb requires a precise version of every other. If you had my job, you'd find out what you needed to know within half an hour.

 

 

So I installed 7.4.2 from source but that confused cabal because my attempt to uninstall the ubuntu package with 7.4.1 in had failed with dependency-hell. Figuring out why (or even that) my packages weren't being seen was the puzzle I was referring to.

So the complaint is about Ubuntu?

I think we all know that package management is tricky and ubuntu are struggling, but that would be another topic.

 

 

The point is that we wouldn't have to be talking about this at all if people didn't move the furniture around all the time. 

That's not a very good point. It sounds as though you're the one who moved furniture around, considering that you managed to mix up Ubuntu's GHC package with your hand-built ones.

Well now you're just playing with words. I've already explained how it happened.

 

[Gregory Collins]

On Fri, May 3, 2013 at 6:48 AM, Adrian May <adrian.ale...@gmail.com> wrote:

May I venture a guess that you never tried to manage a 5-10 million line project?

I build a project a couple orders of magnitude bigger than that dozens of times every day. Similar stories are not uncommon among people who inhabit this list. But thanks, citing that figure as an excuse to be condescending to that person was really worth a giggle this morning. :)

That's what I do. I'm not a programmer, I'm a manager. I run teams of a few dozen people on subprojects within huge telecom-related projects, and my job is to try and keep it all from collapsing in a heap of bugs. 

If you had any experience of that you'd run a mile from any technology with this hit and miss attitude.

You keep saying things like this. Actually, you're in this situation because one or more people within your organization have made a succession of very bad choices. Haskell is not to blame. Personally, I almost can't believe you're taking this tack on the list now that the details of your situation are apparent: you've let a 5-10 million line project spiral out of control without putting the necessary software engineering infrastructure and controls in place.

 

I can't tell people what version they should be using because half of them work for a completely different company. They have their own dependencies coming from other projects that I'm not even allowed to know about.

... and the truth emerges. This issue you're having reflects a lot more strongly on your technical culture than it does on any instability in GHC.

Listen: someone within your organization decided to build a product based on a very old library which is no longer maintained by anyone. If this library were actually critical to your business, you would fork it and either get someone in-house or pay a contractor to fix bugs and keep it up to date. (And there are plenty of people here who might be interested in a contract gig to fix this for you if you asked).

Repeatedly claiming in the most histrionic terms that GHC ought to freeze forever and never deprecate anything again so that you can avoid doing your job properly is simply not realistic, especially given Haskell's social culture (newsflash: it's a research platform), and is not going to garner you any sympathy on this list, either. You could practically be the poster boy for why we have the motto "avoid success at all costs".

You have two options: stay on GHC 6.x (the bits didn't get deleted from the internet), and if that isn't practical, fix Wash (or pay someone to do it if you don't know how) and get on with your life.

G

--
Gregory Collins <gr...@gregorycollins.net>

[Simon Peyton-Jones]

One of the great things about the Haskell mailing lists is the supportive, respectful tone that is the dominant mode of discourse.  I sense that things are getting a little out of control in this particular thread.  Even though this particular issue is clearly extremely frustrating for those involved, it would be great to turn down the emotional temperature.

 

I don’t know why Haskell folk tend to be so generous and helpful, but they really are. (Maybe it’s the hylomorphisms.)  Anyway, let’s keep it that way.

 

Simon

[Adrian May]

 you've let a 5-10 million line project spiral out of control without putting the necessary software engineering infrastructure and controls in place ... This issue you're having reflects a lot more strongly on your technical culture than it does on any instability in GHC.

I can't dictate either that culture or the whole project. I often walk into projects that have been mismanaged for years and try to prop them up. Crap languages are also to blame and that's why I'm interested in Haskell at all. But it's the reality I have to live with. It would be a lot easier for me to sell better languages if they at least paid some heed to backward compatibility.  

Listen: someone within your organization decided to build a product based on a very old library which is no longer maintained by anyone. If this library were actually critical to your business, you would fork it and either get someone in-house or pay a contractor to fix bugs and keep it up to date. (And there are plenty of people here who might be interested in a contract gig to fix this for you if you asked).

Fine. Go ahead and write yourself a blank cheque on my account. Maintenance costs are a fact of life anyway. What I don't understand is why people are trying to maximise them when I'm trying to minimise them.

 

Repeatedly claiming in the most histrionic terms that GHC ought to freeze forever and never deprecate anything again

Now you're putting words into my mouth. I've said from the very first posting that I acknowledge the need for change but would like it to be restricted to stuff that's actually useful and/or necessary instead of changing things just for the hell of it. I'm asking for a compromise. I said that from the start.

 

newsflash: it's a research platform),

That would be a newsflash. I seem to remember it wanting to be a popular quasi-standard FP.

 

and is not going to garner you any sympathy on this list, either. You could practically be the poster boy for why we have the motto "avoid success at all costs".

 

Now you're just being rude.

 

You have two options: stay on GHC 6.x (the bits didn't get deleted from the internet), and if that isn't practical, fix Wash (or pay someone to do it if you don't know how) and get on with your life.

I already found newer libs anyway. 

I really don't know why somebody can't make a simple and well intentioned point without getting attacked by people who feel threatened over every little thing. I said from the start that I think Haskell is cool. I'd just like it to pay a bit more attention to practical issues whilst making progress with its theoretical ones. 

Why don't you just put it in the forum rules that nobody is ever allowed to criticise anything? 

 

At the end of the day, I'm just a typical manager who's atypical in wishing he could tell his programmers to study a bit of Haskell without making it a synch for the manager next door to knife him in the back for suggesting something that looks this unstable. This is the real deal on how Haskell looks out there in the mass market. You can lead a horse to water...

[Ertugrul Söylemez]

Adrian May <adrian.ale...@gmail.com> wrote:

> I really don't know why somebody can't make a simple and well
> intentioned point without getting attacked by people who feel
> threatened over every little thing.

It's because we're failing to see the problem. I mean, if you can
pinpoint the source of your problems we could work on a solution, and we
would be happy to do that. However, it is important to keep in mind
that Haskell is very active and things change a lot. This is not a
problem, it's the mindset of this community. If you are turning it into
a problem, feel free, but then the only suggestion I can make here is
that Haskell is probably not the right choice for your particular
development strategy.

In other words, for Haskell it's simply wrong to assume that you can use
legacy code that hasn't been maintained for many years. Regardless of
whether you like it, this is the way to go. If you want to use Haskell,
be prepared to maintain your code. This usually boils down to making
small adjustments. When the big breaking change in the base library
came I had to adjust a number of type signatures in my projects and I
was done. These adjustments become necessary from time to time, and you
should be ready to perform them.

> I said from the start that I think Haskell is cool.

Unfortunately that doesn't really help. What you are trying to achieve
is a shift in our fundamental philosophy, which is very unlikely to
happen, even if the shift is small. Using Haskell is great, but does
require you to keep up to date.

The other option is to go with old compiler and library versions. They
are all available, if you need them for your project, but this is a bad
solution.

> I'd just like it to pay a bit more attention to practical issues
> whilst making progress with its theoretical ones.

It's very difficult to combine those. Communities solve these problems
differently. Most communities try to keep compatible at the expense of
eliminating much of the potential for innovation. The Haskell community
prefers to go the innovation route and is prepared to repair occasional
breakages. They do occur, and we fix them.

> Why don't you just put it in the forum rules that nobody is ever
> allowed to criticise anything?

Because that's wrong. I criticize things a lot, sometimes with a much
stronger tone than you did. =)

> At the end of the day, I'm just a typical manager who's atypical in
> wishing he could tell his programmers to study a bit of Haskell
> without making it a synch for the manager next door to knife him in
> the back for suggesting something that looks this unstable. This is
> the real deal on how Haskell looks out there in the mass market. You
> can lead a horse to water...

If it's your decision, you shouldn't be afraid to make it. You are the
manager of your team! Don't let yourself be stabbed by another manager.
Recognize that your choice can lead to higher productivity, if you don't
let yourself be distracted by this pointless matter. And yes, it is
pointless. If you simply move on and get to productive Haskell work,
you will find that this is a non-issue.

In particular, you want to make educated decisions, which means that you
should probably research the current standards in the Haskell community.
If you would have performed that research from the beginning, you would
have come to the conclusion that WASH was a bad choice to begin with,
which leads me to another very important point:

I have worked in many SCRUM-based teams. While I could question the
general usefulness of this paradigm, I have to say that it has taught me
a number of very important things, and one thing in particular:
Programmer choices should be made by programmers. You shouldn't have
made the decision about the web framework in the first place. Get a
team of Haskell programmers and let them choose the best tool for the
job.

[Raphael Gaschignard]

On Fri, May 3, 2013 at 4:37 PM, Simon Peyton-Jones <sim...@microsoft.com> wrote:

One of the great things about the Haskell mailing lists is the supportive, respectful tone that is the dominant mode of discourse.  I sense that things are getting a little out of control in this particular thread.  Even though this particular issue is clearly extremely frustrating for those involved, it would be great to turn down the emotional temperature.

I don’t know why Haskell folk tend to be so generous and helpful, but they really are. (Maybe it’s the hylomorphisms.)  Anyway, let’s keep it that way.

Agreed, the thing that surprised me the most when I started reading this list was how nice people were, even when faced with some pretty hostile people.

I think we all agree that dependency management is hard in any system, especially with a lot of generally unmaintained pieces. And the fact that 100% backwards compatibility doesn't seem to be a directive in the language committee like it might be for languages like C++ might frustrate people.

I'm pretty sure most of us have experienced some issue with dependencies breaking , and its probably the most frustrating problem we can have have in any language. It's hard not to take this all a bit personally. Maybe if we think more about how to solve this (getting people to maintain their stuff, for example) we can make the world a better place instead of bickering about issues that are more or less language-agnostic really.

On a side note is there a place where we can see what packages have broken on recent releases?

 

Simon

 

From: haskell-ca...@haskell.org [mailto:haskell-ca...@haskell.org] On Behalf Of Gregory Collins
Sent: 03 May 2013 08:27
To: Adrian May
Cc: Haskell Cafe
Subject: Re: [Haskell-cafe] Backward compatibility

 

On Fri, May 3, 2013 at 6:48 AM, Adrian May <adrian.ale...@gmail.com> wrote:

May I venture a guess that you never tried to manage a 5-10 million line project?

 

I build a project a couple orders of magnitude bigger than that dozens of times every day. Similar stories are not uncommon among people who inhabit this list. But thanks, citing that figure as an excuse to be condescending to that person was really worth a giggle this morning. :)

 

 

That's what I do. I'm not a programmer, I'm a manager. I run teams of a few dozen people on subprojects within huge telecom-related projects, and my job is to try and keep it all from collapsing in a heap of bugs. 

 

If you had any experience of that you'd run a mile from any technology with this hit and miss attitude.

 

You keep saying things like this. Actually, you're in this situation because one or more people within your organization have made a succession of very bad choices. Haskell is not to blame. Personally, I almost can't believe you're taking this tack on the list now that the details of your situation are apparent: you've let a 5-10 million line project spiral out of control without putting the necessary software engineering infrastructure and controls in place.

 

 

I can't tell people what version they should be using because half of them work for a completely different company. They have their own dependencies coming from other projects that I'm not even allowed to know about.

... and the truth emerges. This issue you're having reflects a lot more strongly on your technical culture than it does on any instability in GHC.

 

Listen: someone within your organization decided to build a product based on a very old library which is no longer maintained by anyone. If this library were actually critical to your business, you would fork it and either get someone in-house or pay a contractor to fix bugs and keep it up to date. (And there are plenty of people here who might be interested in a contract gig to fix this for you if you asked).

 

Repeatedly claiming in the most histrionic terms that GHC ought to freeze forever and never deprecate anything again so that you can avoid doing your job properly is simply not realistic, especially given Haskell's social culture (newsflash: it's a research platform), and is not going to garner you any sympathy on this list, either. You could practically be the poster boy for why we have the motto "avoid success at all costs".

 

You have two options: stay on GHC 6.x (the bits didn't get deleted from the internet), and if that isn't practical, fix Wash (or pay someone to do it if you don't know how) and get on with your life.

 

G

--
Gregory Collins <gr...@gregorycollins.net>

[Ertugrul Söylemez]

Raphael Gaschignard <dasu...@gmail.com> wrote:

> I'm pretty sure most of us have experienced some issue with
> dependencies breaking , and its probably the most frustrating problem
> we can have have in any language. It's hard not to take this all a bit
> personally. Maybe if we think more about how to solve this (getting
> people to maintain their stuff, for example) we can make the world a
> better place instead of bickering about issues that are more or less
> language-agnostic really.

The problem can't be solved technically. It's a human problem after all
and it's amplified by the experimentalism in this community. I think
the best we can do is to acknowledge its existence, which places us way
ahead of mainstream programming communities.

We don't pretend that type X in lib-0.1.0 is the same as type X in
lib-0.2.0. What we need to work on is the ability to actually combine
multiple versions of the same package conveniently, i.e. we shouldn't
view this combination as an error.

[Adrian May]

How about this: can you guys give me a detailed example of a justified deprecation: one so extremely obviously called for that even I would agree. I just want to understand the kind of logic that's applied over these things.

[Neil Davies]

Isn't this a problem of timescale?

Nothing can be backward compatible for ever (or at least nothing that
is being developed or maintained)

There will be, in the life of non-trival length project, change.

We rely (and I mean rely) on Haskell s/w that was written over 10 years ago - we accept that
when we want to recompile it (about every 2/3 years as the systems it interacts with are updated)
there will be a cost of change to bring it up to latest libraries etc.

But the joy is that (combined with the regression and property tests around it) we can have very high
confidence that once the "old" stuff recompiles it will operate the same. And as it is key to our business
that is a nice feeling - let's me sleep soundly at night.

The beauty of the Haskell ecosystem is that such change is nowhere as hazardous as with other approaches.
Therefore its total costs are less.

The experimentalism in this community is to be applauded and encouraged - it is spawning robust
solutions to the "real" underlying problems of constructing a society that can actually support the
technical infrastructure it is creating. Don't forget the motivation for Ada was that the projected
costs of supporting the US defence infrastructure was projected to exceed the projected GDP of
the US by 2012. Maintaining essential safety critical systems isn't an optional extra.

We see that the same Ada-like scenario is working its way out in companies today - large Telcos,
Goverment projects etc - I also see that formalism, such as embodied in Haskell, is the ONLY hope
we have to contain the costs of maintenance complexity.

Yes, the underlying issue is a human one - but it lies in the low value given to medium to long
term sustainability of organisations (e.g Telcos) compared to the relative high value that is given
to novelty. Perhaps this is an inevitable by-product of a marketing driven, short term driven
business culture?

Neil

[Ertugrul Söylemez]

Changes already made in the base library or in one of the platform
libraries:

* base: Eq and Show independent of Num. Broke a lot of code. Reason:
Makes function-like numeric types possible.

* base: Deprecated and finally removed the old exception system.
Replaced by extensible exceptions, added new masking system. Broke
a lot of code. Reason: Makes the whole exception handling more
sensible.

* mtl: Unified transformer and Identity variants. Broke some code.
Reason: Makes the internals much more maintainable and the whole
library design more sensible.

* Haskell: Changed the type specializing behavior in local bindings.
Broke a lot of code. Reason: Makes type inference infer more
specialized types, makes code more concise, but occasionally
requires a type signature when you specifically want more
polymorphic types.

Often demanded changes that may or may not happen in the future:

* base: Make Functor a superclass of Monad. One of the two most
commonly demanded change to the base library. Will break lots and
lots of code. Reason: Would greatly simplify a lot of code.

* base: Fix the numeric type classes. The other most commonly
demanded change. Will break lots and lots of code, including most
of the base library. Reason: Would make numeric code much more
sensible and algebraic.

My personal demands. Unlikely to happen in the near future:

* Add RankNTypes, ScopedTypeVariables, TupleSections and TypeFamilies
to standard Haskell. Shouldn't break any existing code.

* Replace all special arrow classes by category classes, i.e. turn
ArrowChoice and ArrowLoop into CategoryChoice and CategoryLoop.
Introduce ApplicativeFix. Will break some existing code.

* Factor Applicative and Alternative into four classes:
- (Functor f) => Apply f (<*>)
- (Apply f) => Applicative f pure
- (Functor f) => Plus f (<|>)
- (Plus f) => Alternative empty
Would break everything. Everything.

I could go on. The point is that you are probably the first person to
complain about those changes. =)

[Ertugrul Söylemez]

Neil Davies <semanticp...@gmail.com> wrote:

> Isn't this a problem of timescale?
>
> Nothing can be backward compatible for ever (or at least nothing that
> is being developed or maintained)

I was referring to the Dependency Hell. I don't consider breaking
changes a problem.

[Adrian May]

Changes already made in the base library or in one of the platform
libraries:

 

So could you pick the most unassailable and tell me more about it please?

[Guy]

Ertugrul Söylemez wrote:
> Often demanded changes that may or may not happen in the future:
>
> * base: Make Functor a superclass of Monad. One of the two most
> commonly demanded change to the base library. Will break lots and
> lots of code. Reason: Would greatly simplify a lot of code.
>
> * base: Fix the numeric type classes. The other most commonly
> demanded change. Will break lots and lots of code, including most
> of the base library. Reason: Would make numeric code much more
> sensible and algebraic.

That's what I thought of when I saw the original complaint - GHC is too backwards compatible! There's far too much
boilerplate because of the Functor => Applicative => Monad mess. Float/Double being Enums is ridiculous. None of this
gets fixed because of the fear that new GHC won't compile old code.

Perhaps we need some system for maintainers to vote on whether they consider the value of a breaking change to be worth
the effort of fixing their packages to work with it. In my own code, I usually find that this effort is minor, and I'm
more than happy to do it in return for a better language/library.

PS The proposal to fix Functor => Applicative => Monad has patches attached for GHC and base, but the backwards
compatibility bogeyman always seems to trump something that will break a lot of code.

[Tobias Dammers]

On Fri, May 03, 2013 at 01:23:55PM +0300, Guy wrote:
> That's what I thought of when I saw the original complaint - GHC is
> too backwards compatible! There's far too much boilerplate because
> of the Functor => Applicative => Monad mess. Float/Double being
> Enums is ridiculous. None of this gets fixed because of the fear
> that new GHC won't compile old code.

>

> PS The proposal to fix Functor => Applicative => Monad has patches
> attached for GHC and base, but the backwards compatibility bogeyman
> always seems to trump something that will break a lot of code.

This kind of "breaks everything" changes would require something similar
to what Python is doing with the 2 -> 3 transition, and considering how
painfully slowly it is progressing there, I understand perfectly well why
people don't want to go there.

[Adrian May]

PS The proposal to fix Functor => Applicative => Monad has patches attached for GHC and base, but the backwards compatibility bogeyman always seems to trump something that will break a lot of code.

I think that should be fixed as well, but it would be tantamount to a new language. 

I guess you need some kind of versioning system for the libraries. Why not put them all in a public source control server and have ghc force people to say which snapshot they wanted. That would be your final breaking change, and it's a one-liner in the Makefile. Then you could thrash around as much as you liked and people like me would have nothing to complain about. Naturally, the compiler itself should keep supporting old modes.

Adrian.

[Ertugrul Söylemez]

I'll just pick a random example: Eq and Show are no longer superclasses
of Num. I'm the author of the Netwire library, a library for functional
reactive programming. Before that change you would write the following
code to express a clock that runs twice as fast as the real time clock
and oscillates up and down while gradually increasing:

liftA2 (\t o -> 2*t + sin o) time (integral_ 0 . v)

Thanks to the change you can now write it as:

2*time + sin (integral_ 0 . v)

[Michael Sloan]

Dependency breakage is certainly an unavoidable problem.  However, I think Haskell is also in a much better position for having a technical solution to the frustration of breakages.

Barring issues with changing datatypes / class instances, we can already express many of the API changes you'd want to make to some library [1].  Now, no one actually does what this proposal suggests - it's a lot of work, and it doesn't work in general.  However, the fact that Haskell makes something like this seem reasonable is heartening.

Of course, even if we had good tools that automatically refactored code to use new APIs, it wouldn't be possible for any non-superficial changes.  Even so, if a good enough refactoring tool existed, and it was popular with both authors and users, a lot of the annoyance of dependency breakages could be removed.

-Michael

[1] http://haskellwiki.gitit.net/The%20Monad.Reader/Issue2/EternalCompatibilityInTheory

[Adrian May]

On 3 May 2013 18:56, Ertugrul Söylemez <e...@ertes.de> wrote:

Adrian May <adrian.ale...@gmail.com> wrote:

> > Changes already made in the base library or in one of the platform
> > libraries:
>
> So could you pick the most unassailable and tell me more about it
> please?

I'll just pick a random example:  Eq and Show are no longer superclasses
of Num.  I'm the author of the Netwire library, a library for functional
reactive programming.  Before that change you would write the following
code to express a clock that runs twice as fast as the real time clock
and oscillates up and down while gradually increasing:

    liftA2 (\t o -> 2*t + sin o) time (integral_ 0 . v)

Thanks to the change you can now write it as: 

    2*time + sin (integral_ 0 . v)

I never doubted that people add new stuff for valid reasons. What I'm interested in is whether or not it could have been done without breaking anything. But having thought about it for a while, I'm tending to think that version controlling all the standard modules is the only general solution. 

You'd have them all in a git ... ahem ... darcs repo which every dev would clone the entire history of. Something prominent in the project would say which version you want. (We could brainstorm about hierarchies of that but it probably wouldn't work anyway.) GHC would just switch its internals according to that number and fetch the right version of the module out of darcs as part of the compilation process. 

If you really wanted to protect people from future changes, you'd make it obligatory to tell ghc which version you want, but seeing as I seem to be more worried about this than anybody else around here, I might as well assume you'd default to the latest, but please, at least issue a warning so that people know this offbeat system even exists.

)

I could have my project source in a completely different source control system cos this darcs interaction is internal to the compiler. 

This ain't gonna mean I don't have to maintain stuff, but having the choice about when to do so would be a great help. Better still, I could take a fifty year old codebase, build it out of the box, and nudge the version along one step at a time so I have some kind of chance, which would render my original post completely redundant. 

But best of all, I'd no longer care which dev had which Haskell Platform version. They'd just get nagged into upgrading ghc whenever it saw a too racy module version. That would mean I could let them finish what they were doing on their own branch, check it into the old-style mainline and then tell them to merge it onto the new-style mainline, expecting a few puzzles along the way. For their next feature they'd branch off the new mainline and in a few weeks the old one would be history. (I'm not sure you've all figured out that those few weeks are necessary.)

Seeing as you guys like theoretical rigour so much, maybe I should put it this way: if you show me a lump of text and call it source code for a program, I'll think you mean that it contains all the information I need to turn it into one. If it fails to specify which versions of which external libraries it assumes are hanging around somewhere, then it hardly meets that definition. Looking at it that way, compiler errors are not the worst thing that could happen: it might build an entirely different program. I've seen two huge projects hit the trash can because of build system vagueness, and that's what I learned out of it.

Just imagine never having to negotiate with the backward-compatibility whingers anymore!

Adrian.

[David Thomas]

I'd also like to see these two.  It occurs to me there may be language tweak that could reduce breakage and add some convenience in both cases.  It would not surprise me at all if this has been thought of, examined, and discarded, but I don't have time to dig so I'll just lay it out quickly, and if it has been discussed before someone will probably know where.

The idea is to allow definitions of superclass operations in subclass instances.  If there are such definitions, it's treated as if there were instances defined for each class (potentially a source translation, even).  I think default definitions of superclass operations in the subclass would be used last (that is, only for the automatic instance of the superclass, and only if the superclass didn't have a default for that).

This should allow existing instances of Num to just work (and I think Monad too, with some care).  It would also mean if you're making something that's a Monad or a Num you could just lay out the one instance in all one place, reducing a bit of boilerplate.  At the same time, you'd have the flexibility to just use the superclasses where you just want pieces.

[Tom Ellis]

On Fri, May 03, 2013 at 09:34:21PM +0800, Adrian May wrote:
> I never doubted that people add new stuff for valid reasons. What I'm
> interested in is whether or not it could have been done without breaking
> anything. But having thought about it for a while, I'm tending to think
> that version controlling all the standard modules is the only general
> solution.

I think you may be overestimating the severity of the "breakage" that
applies to the WashNGo package.

In Haskell2010 a number of module locations were renamed in order to reduce
clutter. For example, IO became System.IO, List became Data.List and Monad
became Control.Monad.

I'm pretty sure that updating all of these module names will fix the
problem. No one has bothered because the package is very old and there are
more suitable alternatives these days.

Tom

[Alexander Solla]

On Fri, May 3, 2013 at 6:34 AM, Adrian May <adrian.ale...@gmail.com> wrote:

On 3 May 2013 18:56, Ertugrul Söylemez <e...@ertes.de> wrote:

Adrian May <adrian.ale...@gmail.com> wrote:

> > Changes already made in the base library or in one of the platform
> > libraries:
>
> So could you pick the most unassailable and tell me more about it
> please?

I'll just pick a random example:  Eq and Show are no longer superclasses
of Num.  I'm the author of the Netwire library, a library for functional
reactive programming.  Before that change you would write the following
code to express a clock that runs twice as fast as the real time clock
and oscillates up and down while gradually increasing:

    liftA2 (\t o -> 2*t + sin o) time (integral_ 0 . v)

Thanks to the change you can now write it as: 

    2*time + sin (integral_ 0 . v)

I never doubted that people add new stuff for valid reasons. What I'm interested in is whether or not it could have been done without breaking anything. But having thought about it for a while, I'm tending to think that version controlling all the standard modules is the only general solution. 

Seeing how type class constraints were removed, obviously, the change could not have been done without breaking code.

On the other hand, the solution is a regular expression away.  Even a 5-10 million line project could survive that, even if it means issuing a ticket, going through testing and QA, etc.

GHC changes are an issue management needs to consider, but the maintenance burden they introduce are minimal and typically mechanically fixable.  If management is unwilling to allocate resources to deal with these issues, then it behooves management to settle on a single version of the Haskell Platform (or even just GHC, if appropriate) or move on to another language, and lose the productivity benefits of Haskell.

You'd have them all in a git ... ahem ... darcs repo which every dev would clone the entire history of. Something prominent in the project would say which version you want. (We could brainstorm about hierarchies of that but it probably wouldn't work anyway.) GHC would just switch its internals according to that number and fetch the right version of the module out of darcs as part of the compilation process. 

If you really wanted to protect people from future changes, you'd make it obligatory to tell ghc which version you want, but seeing as I seem to be more worried about this than anybody else around here, I might as well assume you'd default to the latest, but please, at least issue a warning so that people know this offbeat system even exists.

Surely, as a manager, you have taken at least a basic course in economics.  And you understand how resources, such as open source developer time, are allocated.  Everybody's time is valuable, and the professional academics who work on GHC will use the same economic principles you use (making changes with the highest marginal benefit).  The hobbyist open source developers will do the same thing, except their utility functions will include their personal preferences.

Do you really want this done?  I suggest cash payments to the experience Haskell developer of your choice.

)

I could have my project source in a completely different source control system cos this darcs interaction is internal to the compiler. 

This ain't gonna mean I don't have to maintain stuff, but having the choice about when to do so would be a great help.

You already have that choice. 

[Brandon Allbery]

On Fri, May 3, 2013 at 5:30 AM, Adrian May <adrian.ale...@gmail.com> wrote:

How about this: can you guys give me a detailed example of a justified deprecation: one so extremely obviously called for that even I would agree. I just want to understand the kind of logic that's applied over these things.

This might not be possible because your notion of a justified change may not align with other people's. IIRC the removal of the Show constraint on Num was driven by type level natural numbers? which matter to the type hackers but not to someone whose main concern is getting an unmaintained web interface running. (OTOH it also may not have any effect on said web server, since it mostly affected people who take the somewhat risky action of defining their own Num instances; I suspect the exceptions change would have more impact on web stuff.)

As for the exceptions stuff, that was a multi-step change. Exception handling was somewhat unprincipled and came in two forms, which used the same function names but in different ways. There was support for IO exceptions in the Prelude and conflicting support for general exceptions, which behaved somewhat differently when handed an IO exception, in Control.Exception. One key behavior was that you had to handle all exceptions or none at all; the only way to choose specific exceptions was to handle all of them, inspect the exception object, and rethrow if it wasn't one you wanted to handle. And inspecting the exception object to see what it had in it could be tricky at times, because there wasn't much guidance with respect to user defined exceptions and some library exceptions did things slightly differently from the ones in the base.

The exception cleanup made IO exceptions and other exceptions behave consistently and got rid of the conflicting definitions. This did require source changes, as anyone relying on the Prelude exceptions had to add an import of Control.Exception and anyone using old-style exceptions generally had to add a type annotation to their handler; more ideally, they'd rewrite their exception code to handle specific exceptions or exception classes instead of poking at the exception object to determine whether it was one they cared about or not --- but this was not necessary to get older code running again, only the added type annotation was necessary.

--

brandon s allbery kf8nh                               sine nomine associates

allb...@gmail.com                                  ball...@sinenomine.net

unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net

[Adrian May]

Barring issues with changing datatypes / class instances, we can already express many of the API changes you'd want to make to some library [1].  Now, no one actually does what this proposal suggests - it's a lot of work, and it doesn't work in general.  However, the fact that Haskell makes something like this seem reasonable is heartening.

[1] http://haskellwiki.gitit.net/The%20Monad.Reader/Issue2/EternalCompatibilityInTheory

Thanks Michael, that seems to be what I was talking about, only 8 years earlier, better thought through, and somewhat more readable.

So why do you say it doesn't work in general?

[Ozgur Akgun]

Hi,

On 3 May 2013 11:43, Tobias Dammers <tdam...@gmail.com> wrote:

> PS The proposal to fix Functor => Applicative => Monad has patches
> attached for GHC and base, but the backwards compatibility bogeyman
> always seems to trump something that will break a lot of code.

This kind of "breaks everything" changes would require something similar
to what Python is doing with the 2 -> 3 transition, and considering how
painfully slowly it is progressing there, I understand perfectly well why
people don't want to go there.

There is one very big advantage in the Haskell-world though. 

Most of the struggle will be at the compile time. The biggest headache caused by

the Python 2 -> 3 transition is how you get a runtime error 2 weeks after you think

you've fixed everything!

(Yeah, I know code coverage analysis is an option when you don't have static

type checking, but ...)

Cheers,

Ozgur

[Guy]

David Thomas wrote:
> I'd also like to see these two. It occurs to me there may be language tweak that could reduce breakage and add some
> convenience in both cases. It would not surprise me at all if this has been thought of, examined, and discarded, but I
> don't have time to dig so I'll just lay it out quickly, and if it has been discussed before someone will probably know
> where.
>
> The idea is to allow definitions of superclass operations in subclass instances. If there are such definitions, it's
> treated as if there were instances defined for each class (potentially a source translation, even). I think default
> definitions of superclass operations in the subclass would be used last (that is, only for the automatic instance of the
> superclass, and only if the superclass didn't have a default for that).
>
> This should allow existing instances of Num to just work (and I think Monad too, with some care). It would also mean if
> you're making something that's a Monad or a Num you could just lay out the one instance in all one place, reducing a bit
> of boilerplate. At the same time, you'd have the flexibility to just use the superclasses where you just want pieces.

http://hackage.haskell.org/trac/ghc/wiki/DefaultSuperclassInstances

I'm surprised that the various superclass proposals haven't got more attention, seeing as it would allow for this kind
of class hierarchy clean-up without breaking lots of code.

[David Thomas]

That's approximately what I was describing, yes.  Thanks!

[Adrian May]

I'm having a bit of trouble getting my brain around that, but if anybody cares about attracting new users, that might be relevant in itself. Perhaps I could be seen as an example of your swing-state. I'm no Haskell expert but I'd like to push it if I could cos I'm so sick of seeing huge codebases land in the dustbin due to the evils of imperative coding. The version-controlled modules thing is immediately comforting for me cos I know what it is and I could fire it at the manager next door who doesn't know much but fancies my job. 

[David Thomas]

That's approximately what I was describing, yes.  Thanks!

On Fri, May 3, 2013 at 7:54 AM, Guy <guytsal...@yahoo.com> wrote:

[Brandon Allbery]

On Fri, May 3, 2013 at 10:54 AM, Guy <guytsal...@yahoo.com> wrote:

http://hackage.haskell.org/trac/ghc/wiki/DefaultSuperclassInstances

I'm surprised that the various superclass proposals haven't got more attention, seeing as it would allow for this kind of class hierarchy clean-up without breaking lots of code.

IIRC they've been tried and found to actually cause more backward compatibility issues than they solve because there are so many packages which have created their own instances, and nobody's found a workaround that doesn't either do that or lead to bizarre type errors.

[Tobias Dammers]

Well; this is an additional problem that comes with the pragmatic choice
for a language that doesn't believe in type checking and compile-time
guarantees, but I think it is largely orthogonal. At least
theoretically, you could have 100% test coverage, which would put the
Python project in the same situation as the Haskell one (except that the
tests themselves would also have to be converted...)

The problem I'm talking about, though, is that such a change would split
the ecosystem in two (say, "Traditional Haskell" and "Functor-Correct
Haskell"), just like the 2/3 separation is all over the Python ecosystem
and causes all sorts of headaches. "Should I be using Python 2 or 3" is
not a question that has a simple answer, and that *is* a problem.

>
> Cheers,
> Ozgur

[Niklas Hambüchen]

While I certainly enjoy the discussion, how about addressing one of the
original problems:

On 02/05/13 13:27, Adrian May wrote:
> I just tried to use Flippi. It broke because of the syntax change so I
> tried WASH. I couldn't even install it because of the syntax change.

I just fixed that in https://github.com/nh2/flippi (note that I have
never seen this code before nor even known about it).

https://github.com/nh2/flippi/commit/5e2fa93f82b4123d0d5b486209c3b722c4c1313d

Had to delete 5 imports and convert one time value.

Took me around 3 minutes.

[Edward Kmett]

"Tantamount to a new language" to fix a minor detail in a typeclass hierarchy? That is just histrionic. No language is that stable.

Scala makes dozens of changes like that between minor versions, and while I hardly hold up their development practices as the best in the industry it is still somehow seen as enterprise ready.

-Edward

[Edward Kmett]

So basically it boiled down drop the haskell98 package dependency and use the new exception system, and import the right things to avoid the use of the no longer exported Prelude catch?

[Bardur Arantsson]

On 05/03/2013 06:44 PM, Niklas Hambüchen wrote:
> While I certainly enjoy the discussion, how about addressing one of the
> original problems:
>
> On 02/05/13 13:27, Adrian May wrote:
>> I just tried to use Flippi. It broke because of the syntax change so I
>> tried WASH. I couldn't even install it because of the syntax change.
>
> I just fixed that in https://github.com/nh2/flippi (note that I have
> never seen this code before nor even known about it).
>
> https://github.com/nh2/flippi/commit/5e2fa93f82b4123d0d5b486209c3b722c4c1313d
>
> Had to delete 5 imports and convert one time value.
>
> Took me around 3 minutes.
>

+1

[Bardur Arantsson]

On 05/03/2013 06:49 PM, Edward Kmett wrote:
> "Tantamount to a new language" to fix a minor detail in a typeclass

> hierarchy? That is just histrionic. *No* language is that stable.
>
> Scala makes dozens of changes like that between *minor* versions, and while

> I hardly hold up their development practices as the best in the industry it
> is still somehow seen as enterprise ready.
>
> -Edward

Indeed. It's all turned into absurd hyperbole at this point.

Regards,

[Tom Murphy]

On Thu, May 2, 2013 at 9:48 PM, Adrian May <adrian.ale...@gmail.com> wrote:

Is anybody in the Haskell community still interested in attracting new users? If so I suggest you go play with Ruby on Rails. Then you'll know what it's like to approach a complex and unfamiliar system where every crumb requires a precise version of every other. If you had my job, you'd find out what you needed to know within half an hour.

 

Rails is in many ways as (more?) backwards-incompatible as Haskell. E.g., Rails 4 requires(!) Ruby 1.9.3+. 1.9.3 was released in the fall of 2011. When new major versions of Rails or Ruby come out, developers are generally expected to make the incremental changes to keep up. It's the "donkey in a well" thing -- you never get buried if you make small changes over time.

Tom

[Hilco Wijbenga]

On 3 May 2013 09:44, Niklas Hambüchen <ma...@nh2.me> wrote:
> While I certainly enjoy the discussion, how about addressing one of the
> original problems:
>
> On 02/05/13 13:27, Adrian May wrote:
>> I just tried to use Flippi. It broke because of the syntax change so I
>> tried WASH. I couldn't even install it because of the syntax change.
>
> I just fixed that in https://github.com/nh2/flippi (note that I have
> never seen this code before nor even known about it).
>
> https://github.com/nh2/flippi/commit/5e2fa93f82b4123d0d5b486209c3b722c4c1313d
>
> Had to delete 5 imports and convert one time value.
>
> Took me around 3 minutes.

It seems fair to say that Haskell's designers lean more to evolution
than maintaining backward compatibility. This reminds me of "Go" (the
programming language). The approach chosen by Go's designers was to
create a tool (gofix) that would automatically fix one's code to
comply with the latest standard. See
[http://talks.golang.org/2012/splash.article#TOC_17.] (yes, include
that last period).

Given the apparent simplicity of the changes needed to keep one's
Haskell code up to snuff and the strong typing inherent in Haskell
code, would it not be possible to create something similar? If there
is a tool that moves (most of) one's code from Haskell version n to
n+1 then making breaking changes would be even less of an issue.

Just an idea, I have no clue about its feasibility...

[Nicolas Trangez]

I mentioned the same on #haskell today. Something like Coccinelle
(http://coccinelle.lip6.fr) "semantic patches" could be really useful to
automate (some) API & language changes. Somewhat like (but better than)
the Python '2to3' tool.

I think some message about a GSoC project regarding an AST-based
refactoring tool was posted to this list. That might be a useful
building block for such tool?

Imagine one day whenever a new HP release is made, GitHub pull-requests
are created automatically based on a automatically-generated patch
verified through a compilation&test-cycle on TravisCI for GH-hosted
packages published on Hackage.

Nicolas

[Niklas Hambüchen]

On 04/05/13 01:52, Nicolas Trangez wrote:
> On Fri, 2013-05-03 at 10:40 -0700, Hilco Wijbenga wrote:
>> Given the apparent simplicity of the changes needed to keep one's
>> Haskell code up to snuff and the strong typing inherent in Haskell
>> code, would it not be possible to create something similar? If there
>> is a tool that moves (most of) one's code from Haskell version n to
>> n+1 then making breaking changes would be even less of an issue.
>>
>> Just an idea, I have no clue about its feasibility...
>
> I mentioned the same on #haskell today. Something like Coccinelle
> (http://coccinelle.lip6.fr) "semantic patches" could be really useful to
> automate (some) API & language changes. Somewhat like (but better than)
> the Python '2to3' tool.
>
> I think some message about a GSoC project regarding an AST-based
> refactoring tool was posted to this list. That might be a useful
> building block for such tool?

Yes, I proposed that.

It seems to be already in the making by some, but seems to need more
concentrated community effort/support/contribution.

It would also *hugely* reduce the time spent on what my next email is about.

[Niklas Hambüchen]

All right, here you go: https://github.com/nh2/WashNGo

https://github.com/nh2/WashNGo/commit/08010e7404219470a827f3e4172004f9d2aedc29

Took me around 75 minutes.

Think about it a bit:

I just ported thirty thousand lines of code that I have never seen
before and that has bit-rotted for over six years to the latest
programming environment.

It being Haskell, I am pretty confident it does *exactly* what it's
supposed to do.

I want to see anyone do that with an equivalently sized + outdated Ruby
/ Python project.

On 02/05/13 13:27, Adrian May wrote:
> I just tried to use Flippi. It broke because of the syntax change so I
> tried WASH. I couldn't even install it because of the syntax change. I

> persisted for a while but gave up because getPackageId doesn't exist in
> any form at all anymore. This was only the install script: what would
> WASH itself have in store for me to get my brain around?

[Adrian May]

Well I'm enormously grateful to Niklas for fixing those two things. Simon was right that people are very supportive around here. 

Even though I've been advised against WASH already, it seems important to fix that stuff because it's a liability to Haskell to have broken code kicking around where people might find it. I found flippi just by googling for "haskell wiki engine", in fact I think I was pointed there by wikipedia, and there's nothing on the WASH page to warn anybody. So it's great that Niklas fixed it, thereby preventing impressionable people from having a Rails-day like I did.

But is it correct to extrapolate from the fact that people like you can fix it in 5 and 75 minutes, that everybody else can and that's how industry should calculate its maintenance costs? You guys all know a hell of a lot more about Haskell than I do, but I've been playing with it for a few years now, and I never met anybody independently of Haskell who had even heard of it. 

On 3 May 2013 16:44, Ertugrul Söylemez <e...@ertes.de> wrote:

If it's your decision, you shouldn't be afraid to make it.  You are the

manager of your team!  Don't let yourself be stabbed by another manager.
Recognize that your choice can lead to higher productivity

Middle management in big companies isn't really about minimising maintenance costs, or even getting anything done. It's about building yourself a botnet of colleagues you can trigger to DDoS one another. You don't need much of a trigger: it's the timing that counts: every bot has to perceive the attack to be already underway and successful by the time you trigger them. Then they'll be grateful that you pointed out something they hadn't noticed before, after all, they wouldn't want to screw up with any other bot. The main reason you'd want to DDoS somebody at all is so that all your bots know the network is operational and that they're safer on the inside. That's why most managers spend more time trying to sabotage one another's projects than doing anything useful themselves, and why the most useless of them always wind up at the top.

It's in that context that I'd like you to try and imagine why my priorities might be different from yours. Please don't say that it's my culture's fault. That would be true, but it wouldn't be helpful because if nothing improved in the last 3000 years it probably won't in the next 3000 either.

Whether a manager wants to behave in this Machiavellian way or not, he'd better assume that he's surrounded by botnets that want him on the inside. If he has any aspirations to keep both his job and a modicum of autonomy, he wouldn't want to give them a trigger on a plate. Backward compatibility is a very potent trigger because everybody knows what it means, and it would be potty to imagine you could convert somebody else's botnet into mutinying against the controller with the notion that backward compatibility doesn't matter. Referential transparency is not a very good defence because nobody knows what you're talking about.

Take a guess how fast I can hire programmers here in Taiwan: about once every 3 months. I turn down 90% of applicants cos I know they'd waste more of my time than they save. I'm talking about the kind of people who can spend a whole week wondering why the bug never changes before I come along and ask them if they're even editing the right file. It's not obvious to people in my position why writing a coding standard that says "nobody is allowed to write anything that a monkey wouldn't understand" is a bad idea.

Hopefully I've now shown that I must be nuts to be interested in Haskell at all. So why am I? Well I described my OP as a lullaby, not a rant. If you want to hear a rant, ask me what I think of imperative programming. Last time I saw an 8 million line project land in the bin, I could have said that I'd told them so 2 years earlier, but instead, I actually shed tears for all the developers who'd been stuck in that office til 11 every night, chasing bugs around in circles that could never be fixed. For the guy who was publicly humiliated for giving a presentation about how to track a bug down through all that spaghetti and then fix it by wrapping "if (p!=NULL)" around the crash instead of wondering what was null or why, when in all fairness, that was the only thing any of them ever did. For that whole quirky culture that refers to bugs by a six-digit ID beginning with 3, and that doesn't lose it's cool even after two months unable to even build the thing, followed by another two when it can't make it to the idle screen without crashing. Of course I knew it would be pointless to ask those self-satisfied architects if they'd finally figured out that it wasn't smart to riddle the build system with cyclic dependencies so the testers didn't even know what they were testing, or to chop the whole thing into a guzzillion separate pseudo-processes so every debugger would spend 90% of his time trying to single-step over those asynchronous interfaces. Did they fail? I'm afraid not. The controllers just rounded up their best bots, found another venture capitalist and proudly boasted about how they'd turned 2 million lines into 8 in only two years. How would the VC know to ask why they needed all those lines if no new features were coming out? 

You thought I was pissed off with Haskell? Oh no. That's not what I'm pissed off about.

But I'm still not crazy enough to start a project at work in Haskell: what I'm debating is whether or not to give people a few presentations and a few hours in the week to study your language in the hope that it will improve their imperative code, plant a seed of suspicion that OO might not be the last word, nurture a healthy fear of data, and perhaps one day take over Haskell stuff that I might foolishly dare to write for the company. This language has got an important message for the world, and the reason I'm trying to tell you guys this stuff is that I want it to get through.

Once they sent a security consultant to lecture us about how to avoid writing vulnerabilities through which people could jailbreak their phones from the network. Towards the end of the day when he'd explained how buffer overflows work, he dropped "using a language other than C/C++" into his list of possible remedies. The whole room was immediately filled with uproarious laughter. I have to go at this gently and ensure that the carrot looks bigger than the stick at all times. And I can't make myself vulnerable to easy pot-shots about backward compatibility or anything else. 

So what would their first impression be? They'd be dazzled but scared. ***Please bear in mind that if I scare a report by making him feel that his job security depends on him learning something new or taking more responsibility, then he's liable to throw a tantrum and plot against me in self defence.*** If most of his colleagues also think I'm crazy to be going on about this offbeat language, then I'm toast. At the beginning they'll spend a lot of time feeling humiliated by it always saying No, and there'll be a strong tendency for them to say:

 

    "It's not my fault: none of the examples on the web work either, and not even Adrian can make them work." 

At that point I look like an idiot and Haskell at that company will be caught in the crossfire of my assassination. That's why breaking old code is best avoided (as long as it doesn't conflict with progress) especially in a world where lots of unmaintained stuff is still on the web. 

That's why I'm very grateful to Niklas for fixing that prehistoric code. And why I think it's better only to deprecate things if you really need to. Does that make me ultra-conservative? Where I work, conservative is when you're still worried about how long it takes to dereference a virtual.

Do you finally see where I'm coming from? If you want this language to catch on, you have to think about programming the people, not just the computers. You could also just soldier on as a brilliant microculture until you get swamped by something like F# that's not even where you were in 98, and one day people will tell you "Haskell? Monads? That's not what I mean by FP. FP is something like F#." (Apologies to anybody who works on F#: my issue with it is that nobody I know is likely to figure out the functional way to do something if it's that easy for them to bottle out and do it the imperative way.)

Maybe that is the new plan. Maybe Haskell already gave up wanting to be anything but a research platform. Maybe you guys calculate that if I really want to push FP I should be pushing some hybrid like F# or Ocaml. Remember how C++ succeeded where Smalltalk failed because it sneaked the changes under the table instead of calling for revolution. If that is the plan then I'd appreciate somebody putting me in the picture. Otherwise, please try to understand that the problems I'm up against are not about whether Num is derived from Eq or whatever.

mfG,

Adrian.

 

[Niklas Hambüchen]

I think you missed my point.

My point was to show that what you understand as "backward
compatibility" here is totally delivered by Haskell and its environment,
and how easy it is to be "conservative" (where "keeping it running" as
it is is only a matter of renaming a few imports).

> it seems important to fix that stuff

It is not.

I did not "fix" Flippi nor WASH; it is the same unmaintained code that
you should not use. If there's a security hole or it just doesn't work,
nobody will fix it, nobody will even mention it or care, because it is
clear that this is code from the past.

> it's a liability to Haskell to have broken
> code kicking around where people might find it.

There really is no reason to delete open-source code.

> and there's nothing on the WASH page to warn anybody.

The fact that it doesn't build and that the last change is from 2007 the
*is* the warning that it is completely unmaintained and not the way to
do things today.

(One could even say that by making it build on 7.6, I have removed this
warning and given the illusion that everything is fine.)

Of course I agree that it would be better if there were warnings on
their web sites that said "sorry guys, this project is dead now".

I would even be happy with newhackage sending every package maintainer a
quarterly question "Would you still call your project X 'maintained'?"
for each package they maintain; Hackage could really give us better
indications concerning this.

Still I'd say that in this case, the fact that it did not build, hasn't
had a single change in the last half decade, and that you cannot find
any recent discussion about it anywhere on the Internet, make it pretty
clear what is going on here, even for non-technical people.

> Please don't say that it's my culture's fault.

From your story it sounds like you have a problem with developer
simplemindedness and management wars idiocy.

I believe you that that's how it goes in many large organizations.

Nobody is forcing you to be part of that.

There are a lot of places that would care about you trying to get
software development right (it sounds like you do) and, surprise, the
chances that they use something like Haskell are much higher. Not
because they like research platforms, but because it's one of the
reasons for their success.

On 04/05/13 16:06, Adrian May wrote:
> Even though I've been advised against WASH already, it seems important
> to fix that stuff because it's a liability to Haskell to have broken
> code kicking around where people might find it. I found flippi just by
> googling for "haskell wiki engine", in fact I think I was pointed there
> by wikipedia, and there's nothing on the WASH page to warn anybody. So
> it's great that Niklas fixed it, thereby preventing impressionable
> people from having a Rails-day like I did.
>
> But is it correct to extrapolate from the fact that people like you can
> fix it in 5 and 75 minutes, that everybody else can and that's how
> industry should calculate its maintenance costs? You guys all know a
> hell of a lot more about Haskell than I do, but I've been playing with
> it for a few years now, and I never met anybody independently of Haskell
> who had even heard of it.
>
> On 3 May 2013 16:44, Ertugrul Söylemez <e...@ertes.de

> On 4 May 2013 02:33, Niklas Hambüchen <ma...@nh2.me <mailto:ma...@nh2.me>>

> wrote:
>
> All right, here you go: https://github.com/nh2/WashNGo
>
> https://github.com/nh2/WashNGo/commit/08010e7404219470a827f3e4172004f9d2aedc29
>
> Took me around 75 minutes.
>
> Think about it a bit:
>
> I just ported thirty thousand lines of code that I have never seen
> before and that has bit-rotted for over six years to the latest
> programming environment.
>
> It being Haskell, I am pretty confident it does *exactly* what it's
> supposed to do.
>
> I want to see anyone do that with an equivalently sized + outdated Ruby
> / Python project.
>
>
> On 02/05/13 13:27, Adrian May wrote:
> > I just tried to use Flippi. It broke because of the syntax change so I
> > tried WASH. I couldn't even install it because of the syntax change. I
> > persisted for a while but gave up because getPackageId doesn't
> exist in
> > any form at all anymore. This was only the install script: what would
> > WASH itself have in store for me to get my brain around?
>
>

_______________________________________________

[Ben Doyle]

You might want to check out FPComplete, if you haven't already. They're far more focused on making it easy for organizations to adopt Haskell than the community can be. As they say: "Where the open-source process is not sufficient to meet commercial adoption needs, we provide the missing pieces."

[Carter Schonwald]

What pray tell are those missing pieces? Aren't they mostly building a browser based ide plus doing training courses ?

On May 4, 2013 1:42 PM, "Ben Doyle" <benjamin.p...@gmail.com> wrote:

You might want to check out FPComplete, if you haven't already. They're far more focused on making it easy for organizations to adopt Haskell than the community can be. As they say: "Where the open-source process is not sufficient to meet commercial adoption needs, we provide the missing pieces."

[Ben Doyle]

> What pray tell are those missing pieces? Aren't they mostly building a browser based ide > plus doing training courses ?

Sure, and I believe they plan to have that browser-based IDE talk to a virtual server, with a compiler and set of libraries they maintain. That'd solve Adrian's problems, no? So long as he can bring himself to use Yesod over WASH?

Perhaps more importantly, they're well-spoken and business-savvy, and they can persuasively promise that they'll make a risk-averse corporation's (overblown) worries go away. If he's in a management battle, he ought to know where to hire some mercenaries. 

[Adrian May]

Oops, forgot hit hit reply-all the first time, well spotted by Niklas...

---------- Forwarded message ----------
From: Adrian May <adrian.ale...@gmail.com>
Date: 5 May 2013 14:22
Subject: Re: [Haskell-cafe] Backward compatibility
To: Niklas Hambüchen <ma...@nh2.me>

The fact that it doesn't build and that the last change is from 2007 the
*is* the warning that it is completely unmaintained and not the way to
do things today.

(One could even say that by making it build on 7.6, I have removed this
warning and given the illusion that everything is fine.)

That only makes sense if you assume everybody is familiar with Haskell and its culture. But that neglects trying to make it attractive to people who aren't.

Of course I agree that it would be better if there were warnings on
their web sites that said "sorry guys, this project is dead now".

I would even be happy with newhackage sending every package maintainer a
quarterly question "Would you still call your project X 'maintained'?"
for each package they maintain; Hackage could really give us better
indications concerning this.

Something like that would make a lot of sense to me. 

 

Still I'd say that in this case, the fact that it did not build, hasn't
had a single change in the last half decade, and that you cannot find
any recent discussion about it anywhere on the Internet, make it pretty
clear what is going on here, even for non-technical people.

Half a decade is nothing to most programming cultures.

A newbie looks for sample code and blames himself if he can't get it working.

 

> Please don't say that it's my culture's fault.

From your story it sounds like you have a problem with developer

simplemindedness and management wars idiocy. Nobody is forcing 

you to be part of that. There are a lot of places ...

Perhaps I'd rather help those who need it than preach to the converted.

You summed it up nicely as two problems: (1) bitchy managers and (2) untrained programmers. I'd like to use Haskell to help with (2) but I still have to work around (1). My plan is to start by winning the hearts and minds of the developers before sticking my neck out far enough to get it severed. There's another plan where I'm pitching VCs about a start up, in which case I'd have a lot more control, but I'd still have to prove that my elite imperative squad were willing and able to learn a new trick before committing myself.

I've actually learned quite a lot from this discussion and that largely enables me to preempt any Rails-day problems. But that's only me. Lots of people might be flirting with Haskell just out of curiosity and bouncing off it for these reasons. There have been a lot of good ideas suggested about how to minimise that, and I'd also throw in that it would be cool if people could tell the compiler to behave as it did half a decade ago when the code was written so people could prove to themselves that the code works in principle, then they could clock the compiler forward little by little, reading its release notes along the way. That's a lot friendlier than being confronted with an apparently endless series of error messages when you've barely learned to read them, and not even knowing if you're making things better or worse. If the desired compiler/modules version was in the makefile, that, I think, would be a general solution.

The FPComplete thing also looks helpful. I could use that to sell the language to newbies. The mercenaries would come later though. 

Thanks to everybody for helping out with this. 

Adrian.

[Simon Marechal]

On 05/05/2013 11:41 AM, Adrian May wrote:
> Half a decade is nothing to most programming cultures.
> A newbie looks for sample code and blames himself if he can't get it
> working.

I ran into this kind of trouble when I was starting to learn Haskell. I
had error messages like that :

test.hs:1:8:
Could not find module `List'
It is a member of the hidden package `haskell98-2.0.0.2'.
Use -v to see a list of the files searched for.

I then proceeded to figure how to include this haskell98 package, and
later ran into other problems. Perhaps this message could be hard coded
to tell the user that this is deprecated code, and he should use
Data.List instead. This certainly would be friendlier, but I am unsure
it would change anything about adoption:
* all major tutorials are up to date
* almost everyone understands the concept of bit rot, and, as it has
been demonstrated, it is much more manageable than with other
"production ready" languages
* google works fairly well

Everything changes all the time in the javascript and ruby world, but
this doesn't seem to reduce adoption.

There have been several people pointing out the case of PHP. I would say
that with an ageing codebase, you can't upgrade your distribution
because the little things that change will break your code in places you
don't even imagine. With a 10 years old Haskell program, you can choose
to upgrade the codebase, or you can stick with your old binary.

> it would be cool if people could tell the compiler to behave as it did
> half a decade ago when the code was written so people could prove to
> themselves that the code works in principle, then they could clock the
> compiler forward little by little, reading its release notes along the way.

But how would that work ? You would need some archaeologist to tell you
how old the code is so that you could give the proper flags to the
compiler. But if you know how to do that, then you know exactly how to
fix the code.

But you already can do this all by yourself : just install every compilers.

[Raphael Gaschignard]

On Sun, May 5, 2013 at 8:25 PM, Simon Marechal <si...@banquise.net> wrote:

I ran into this kind of trouble when I was starting to learn Haskell. I

had error messages like that :

test.hs:1:8:
    Could not find module `List'
    It is a member of the hidden package `haskell98-2.0.0.2'.
    Use -v to see a list of the files searched for.

I then proceeded to figure how to include this haskell98 package, and
later ran into other problems. Perhaps this message could be hard coded
to tell the user that this is deprecated code, and he should use
Data.List instead.

Forgive me if I'm wrong, but I feel like I've seen such "suggestions" in GHC errors before.

If so, does that mean there's some sort of mechanism in the compiler already in place for such error recognition? Like some simple pattern stuff?  If not, I think that it might not be bad to consider this stuff (misused packaged, changed semantics that create compiler errors), and to put something into place for future modifications. This could make it a lot easier to deal with unmaintained code.

[ami...@gmail.com]

+1

Tom

_______________________________________________

[Brandon Allbery]

On Sun, May 5, 2013 at 7:55 AM, Raphael Gaschignard <dasu...@gmail.com> wrote:

Forgive me if I'm wrong, but I feel like I've seen such "suggestions" in GHC errors before.

If so, does that mean there's some sort of mechanism in the compiler already in place for such error recognition? Like some simple pattern stuff?  If not, I think that it might not be bad to consider this stuff (misused packaged, changed semantics that create compiler errors), and to put something into place for future modifications. This could make it a lot easier to deal with unmaintained code.

There's some very limited capability now; the GHC folks are tossing around ideas for something more general like that.

[Alberto G. Corona]

The case of WASH is a pity. Architecturally It was more advanced that many recent haskell web frameworks.  The package would have been a success with little changes in the DSL syntax.

I suspect that there are many outstanding packages with great ideas abandoned, like WASH

 

2013/5/5 Brandon Allbery <allb...@gmail.com>

_______________________________________________
Haskell-Cafe mailing list
Haskel...@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe

--
Alberto.

[Darren Grant]

Just to be clear,  is WASH beyond redemption,  or would it be worth reviving again? If so,  why?

Cheers,
Darren

[Tom Ellis]

On Sun, May 05, 2013 at 10:46:23PM +0200, Alberto G. Corona wrote:
> The case of WASH is a pity. Architecturally It was more advanced that many
> recent haskell web frameworks. The package would have been a success with
> little changes in the DSL syntax.

Could you briefly summarise the difference between WASH's approach and that
of the more recent frameworks?

[Alberto G. Corona]

Well, the main one is  that is in the group of continuation based frameworks, like other advanced web frameworks such are seaside (smalltalk) ocsigen (ocaml) or coccoon (JavaScript)  . That means that it is not based on the event model, and the  flow is in a single procedure. This makes the navigation much more readable, as a console application. But WASH is  not continuation based, but log based, and the log was stored in the client, that means that it was also restful to a certain level. That approach solved the big problems of memory usage and serialization of continuation based frameworks.

 

It also solved the problem of form safety before the development of formlets and the widespread of applicative functors.

 

But I do not pretend to resucitate WASH. I just miss a continuation of this line of work , but this was not the case. 

 

I  took a deeper look at WASH after developping MFlow, years after the discontinuation of WASH. MFlow coincidentally, is log based in a different way. I supposed that it was based on continuations, and I didn't like them, but it was not. If the project would have been prosecuted, who knows...It had a edge over other web developments in other languages, but it was hard to understand, just because the approach was original and unique. 

 

I consider MFlow as a continuation of WASH in "philosophical" terms.

2013/5/6 Tom Ellis <tom-lists-has...@jaguarpaw.co.uk>

--
Alberto.