Next BAHUG meeting will be held on Monday, February 22 at 7pm at Engine Yard (SOMA, San Francisco):
Engine Yard
500 Third Street, Suite 510
San Francisco, CA 94107
Contact cell (mine): 415-570-1669.
Host's phone (Larry's): 407-718-7665
1. Larry Diehl is going to give a talk on Agda <http://wiki.portal.chalmers.se/agda/>
2. -- to be defined -- (unless somebody else volunteers to give a talk, I can prepare a talk either on Finger Trees, or on Control.Applicative, or probably something else)
Please forward this email to those who may be interested in attending. If you plan to attend, please subscribe to BAHaskell Google Group <http://groups.google.com/group/bahaskell> to follow all the discussions related to this meeting.
Looking forward to this!
> 2. -- to be defined -- (unless somebody else volunteers to give a talk, I
> can prepare a talk either on Finger Trees, or on Control.Applicative, or
> probably something else)
I vote for finger trees, there are lots of good articles out there on
applicative already.
BTW, googlegroups sets reply-to to the group by default, which is sort
of weird because it makes 'reply' work just like 'reply-all', and
harder to respond to individuals. Any argument against turning it
off?
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I also like it the way it is.
--
Jason Dusek
Me too!
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Jason Dusek
On Feb 9, 8:49 pm, Jason Dusek <jason.du...@gmail.com> wrote:
> 2010/02/09 Evan Laforge <qdun...@gmail.com>:
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having missed the talk... why wouldn't one use
* epigram
* ats
* or even coq?
Larry didn't give a talk on why we should use Agda; he just
gave a talk on Agda (while mentioning a few other systems,
too, as they came up in questions).
--
Jason Dusek
Vlad's comment led me further to wonder what else besides Agda might be cool.
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re: coq, Jake Donham (http://www.cs.cmu.edu/~jdonham/) could, since he
gave such a talk a while back when bayfp was still in business.
Thanks for the plug, but it was Twelf actually. Video and slides here:
http://www.bayfp.org/blog/?p=23
If you know one of the FP-style systems like Coq or Agda, you might
find Twelf interesting because it is based on logic programming, and
because it supports a built-in notion of binding (higher-order
abstract syntax) which makes it particularly suited for proofs about
programming languages.
Jake
P.S. anybody interested in reviving BayFP? Personally I think we FPers
of different language tribes have more to unify than to divide us.
--
Jason Dusek
Sent from my iPhone
What we don't want is for it to expand "downward" (less
static, less pure) or splinter into a group for each theorem
prover (like what happened to BayFP).
We don't need to make a point of welcoming formal methods.
That's why we learnt Haskell in the first place. Let's just
have some more formal talks or workshops.
--
Jason Dusek
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Jason Dusek
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oh, man, i'm already into the alzheimers? :(
If you have access to Google wave you can find it by looking at the
bahaskell group's waves. If you don't have access to google wave and
would like and invite let me know.
-Corey O'Connor
--Peter
Cheers,
Corey O'Connor
Why do we need a poll? If we ever take issue with a talk, for example,
if we feel that a talk on Coq is not appropriate, then we might have
to come back to our charter and chat about it. However, I don't think
we have any need to legislate or decide anything. We'd all like to see
an Epigram/Coq/Twelf talk.
--
Jason Dusek
I flailed around a little and then clicked on
"baha...@googlegroups.com" in contacts.
On Tue, Feb 23, 2010 at 3:54 PM, Jason Dusek <jason...@gmail.com> wrote:
> Why do we need a poll?
But we like playing with tech :)
It's not about tech. It's about people.
--
Jason Dusek
if there is ever a chance of having the odd meeting or so in the south
bay, that might let some of us actually attend in person to boot :-)
sincerely.
it never ceases to amaze me that supposedly otherwise intelligent
people say things like, "well, *i* don't have this problem, therefore
logically *you* must not have it, either!"
sincerely.
sincerely.
How do those living in the South Bay feel about that?
--
Jason Dusek
my personal $0.02: anything north of PA starts to suck, so PA and south is nice.
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Here is that email.
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Jason Dusek
---------- Forwarded message ----------
From: Luke Palmer <lrpa...@gmail.com>
Date: 2009/12/29
Subject: Re: [Haskell-cafe] Alternatives to type classes.
To: Jason Dusek <jason...@gmail.com>
Cc: haskell <haskel...@haskell.org>
On Tue, Dec 29, 2009 at 6:22 PM, Jason Dusek <jason...@gmail.com> wrote:
> Consider the real numbers. They "are" a group. We have an
> identity element `0', inverses and closure under the associative
> operation `+'.
>
> Group+ = (+, 0, -1 * _)
>
> They are another group, too -- the group with `*':
>
> Group* = (*, 1, 1 / _)
Ignoring 0 for sake of discussion.
> This seems like a real problem with the whole notion of
> typeclasses -- we can't really say a set/type "is" its
> extension with some new operations.
>
> One road to go on this is to make every extension of the set
> with new ops a different type; but that seems really horribly
> inconvenient. I wonder what approaches have been tried here?
I consider typeclasses a happy notational medium. They are not
perfect, they miss some cases, but they are pretty good.
For full generality at the expense of some verbosity, I like Agda's
solution pretty well. Agda allows you to "open" a record into a
scope.
record Group (a : Set) where
field
_+_ : a -> a -> a
-_ : a -> a
0 : a
conj : {a : Set} -> Group a -> a -> a -> a
conj g x y = x + y + (-x)
where open g
Maybe I even got the syntax right :-P
The cool thing is that you can use this for the invariant-keeping
property of typeclasses, too. Eg. Data.Map relies on the fact that
there is at most one Ord instance per type. By parameterizing the
module over the Ord record, we can do the same:
record Ord (a : Set) where ...
module MapMod (a : Set) (ord : Ord a) where
Map : b -> Set
Map = ...
insert : {b : Set} -> a -> b -> Map b -> Map b
insert = ...
...
So we have the liberty of being able to use different Ord instances,
but different Ord instances give rise to different Map types, so we
can not violate any invariants.
You can do something similar in Haskell using an existential type,
although it is very inconvenient:
data Ord a = ...
data MapMod map a b = MapMod { empty :: map a b, insert :: a -> b ->
map a b -> map a b, ... }
withMap :: Ord a -> (forall map. MapMod map a b -> z) -> z
withMap ord f = f ( {- implement MapMod here, using ord for ordering }- )
Then you could use maps on different Ords for the same type, but they
could not talk to each other.
Some syntax sugar could help the Haskell situation quite a lot.
Slideshare crews with formatting, here is the raw google doc: http://is.gd/8YXM9On Mon, Feb 22, 2010 at 10:36 PM, larrytheliquid <larryth...@gmail.com> wrote:
Slides: http://www.slideshare.net/larrytheliquid/intro-to-agda
On Feb 9, 8:49 pm, Jason Dusek <jason.du...@gmail.com> wrote:
> 2010/02/09 Evan Laforge <qdun...@gmail.com>:
>
> > > We are going to have two talks:
>
> > > 1. Larry Diehl is going to give a talk on Agda
> > > <http://wiki.portal.chalmers.se/agda/>
>
> > Looking forward to this!
>
> Me too!
>
> --
> Jason Dusek
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Respectfully,
Larry Diehl
www.larrytheliquid.com
Cheers,
-Mark
2010/3/16 Joseph Wofford <joseph....@gmail.com>:
--
Jason Dusek
On Apr 5, 12:16 pm, Larrytheliquid <larrytheliq...@gmail.com> wrote:
> April 14th works as far as EY is concerned.
>
> On Mon, Apr 5, 2010 at 12:08 AM, Ivan Tarasov <ivan.tara...@gmail.com>wrote:
>
>
>
>
>
> > I agree, we should postpone.
>
> > This week would probably be too soon, how about Wednesday next week (April
> > 14)?
>
> > Ivan
>
> > On Sun, Apr 4, 2010 at 11:53 PM, baguasquirrel <baguasquir...@gmail.com>wrote:
>
> >> Would it hurt to postpone it a few days so that Larry can recover from
> >> his jet lag first?
>
> >> On Apr 4, 5:05 pm, Jason Dusek <jason.du...@gmail.com> wrote:
> >> > I am not able to make the 5th.
>
> >> > --
> >> > Jason Dusek
>
> >> --
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>
> > --
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