Markdown Interpolation

[Evan Czaplicki]

I just implemented this on the markdown branch. You can embed arbitrary expressions in markdown using double curly braces. (please no bug reports yet, I implemented it today as an experiment)

Here are some examples you can look through (and run once you move to the new branch).

Let me know what you think of this. I feel like I should add more restrictions, but maybe I am being overcautious.

[Joseph Collard]

At a glance, this looks great! I will rewrite my directory page over the weekend using this (scrapping my css flag) and let you know how it goes.

Joe

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[Evan Czaplicki]

Okay, very glad to hear that :) I am thinking of how to nicely allow a limited set of style flags for a markdown block. I am imagining a record that lets you set leading, typeface, etc. but I have not been able to think of an acceptable syntax for this yet.

One way may be to change the type of markdown blocks to TextBlock and then have something like this:

format : TextStyle -> TextBlock -> Element

main = format { defaultStyle | leading <- 2 } [markdown| hats on racks on racks |]

This seems alright, but I feel like it could be better. Any other ideas?

[Joseph Collard]

I think it should be:

format : [TextStyle] -> TextBlock -> Element

where TextStyle is something like:

data TextStyle = Bold | Italic | FontSize Int | ... 

My $0.02

Joe

[Joseph Collard]

On a second look, the way you had it is fine. I didn't realize TextStyle was a record.

Joe

[Jeff Smits]

Looks great Evan :)

I think formatting it like you propose is fine. But would the expected behaviour be that this formatting overrides that of interpolated values?

[sh...@sheeo.dk]

I love this feature -- really makes Elm a potential killer language for writing interactive articles.

[Evan Czaplicki]

Thanks :) How I'm thinking of it, it would not override anything. The goal of this record would be to specify text layout things that do not belong at the level of text. Currently my list of things that belong in the record include:

• line spacing
• fonts for paragraphs, headers, and code
• syntax highlighters for code blocks (perhaps this could also be a record that's easy to mess around with)
  
• padding for paragraphs

I think margins and borders do not belong here. They can be done with embedded elements. Are there any other things that maybe belong in this group?

[Evan Czaplicki]

sheeo, that's a really great way of framing it! :D

Perhaps this also makes Elm closer to the "traditional" workflow. The words people can create markdown blocks. The designers can create widgets using only Elements and Forms (way easier than CSS and HTML) resulting in pure functions from data to graphics. The coder can work on the diagrams and interaction. I'm not sure how much I believe in this division of labour in general (coders write better code), but it seems plausible.

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[Alex Shroyer]

Would this be a way to get Tangle-like interaction in a document?  Would the interpolated Element/Form be able to tell if I click/drag it?

[Evan Czaplicki]

Yes, as long as drags can be detected on Elements and Forms. So the hoverable API would probably make this possible, like this. (looks like there may be a display bug with hoverable elements.)

[Evan Czaplicki]

markdown branch is now merged into the dev branch. Go to the dev branch to use this feature!

[Alex Shroyer]

Noob Git question: How does one "go to" or "move to" a particular branch of Elm?

Is it just git clone <git clone url> ?

[Jeff Smits]

if you have cloned the git repo, use git checkout <branchname>

in this case git checkout dev

On Tue, Oct 29, 2013 at 4:28 PM, Alex Shroyer <ashr...@gmail.com> wrote:

Noob Git question: How does one "go to" or "move to" a particular branch of Elm?

Is it just git clone <git clone url> ?

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[Evan Czaplicki]

Yeah, so it'd be this process:

git clone https://github.com/evancz/Elm.git

cd Elm

git checkout dev

cabal install

You can also use the following command to see what branch you are on:

git status

I use the "GitHub for Mac" application for most things. It is nice and covers all of the basics. You can learn the command line things as they become necessary.

[Alex Shroyer]

Thanks Jeff and Evan!

[Joseph Collard]

I am just now trying to use the markdown interpolation but every time I use it, the output for the interpolation is {{ ... }}. Any idea what I might be doing wrong?

Joe

[Evan Czaplicki]

Which branch are you on?

[Joseph Collard]

I was on the dev branch. However, I just did a pull and recompiled and it seems to be working correctly now.

Joe

[Joseph Collard]

However, it should be noted that the latest dev branch breaks the Sprite library.

AnimationTest using the latest elm-runtime.js can be found here: 

http://people.cs.umass.edu/~jcollard/GalagaBroken/AnimationTest.html

[Evan Czaplicki]

I think I know the bug you are seeing. I think it showed up in Chrome 31. They changed the behavior of caching of images in JS. When you create a new Image(url) it no longer caches the result, so the onload event gets called every time a new image is created. This can actually cause an infinite loop in the renderer and mess things up pretty catastrophically.

I think this means we need to implement some sort of image url cache to deal with this.

[Alex Shroyer]

Just tried to build the dev branch (using the command:  cabal install --force-reinstalls) and got this error:

[13 of 48] Compiling Parse.Helpers    ( compiler/Parse/Helpers.hs, dist/build/Parse/Helpers.o )

compiler/Parse/Helpers.hs:17:19:

    Module `Text.Read' does not export `readMaybe'

cabal: Error: some packages failed to install:

Elm-0.10.0.2 failed during the building phase. The exception was:

ExitFailure 1

Suggestions?  I'm using Ubuntu 12.10 on ARM have had some issues with Haskell packages in the past which were solved with additional build constraints.

[Mads Flensted-Urech]

I see the same thing, also on ubuntu 12.04.

Strange thing is that a seach on hoogle shows no (relevant) hits for readMaybe

[Evan Czaplicki]

Can you check to see if the relevant library had a new release recently? I don't know if hoogle searches "old" APIs.

[Mads Flensted-Urech]

This problem is related to GHC version. I was building with 7.4.2, but the above API change requires the newer base package that is part of 7.6.x . 

So one of the packages that Elm depend on depend on a newer version of base. This shows how important it is that a package manager at least manages dependencies to the base/core correctly, i.e. cabal should be choosing the highest possible version within the boundaray of the current base/core. Something think about in elm-get.

I am currently working on some scripts to setup docker containers with a working version of ghc and building different version of elm. I'll post separately about that once it works.

[Evan Czaplicki]

I switched out that dependency in the dev branch so it no longer needs readMaybe. Does that resolve the issue for you guys? Sorry for the trouble!

[Alex Shroyer]

Well dang.  

[47 of 47] Compiling Main             ( compiler/Compiler.hs, dist/build/elm/elm-tmp/Main.o )

Linking dist/build/elm/elm ...

Custom build step: compiling standard libraries

elm: internal error: setNumCapabilities: not supported in the non-threaded RTS

    (GHC version 7.4.2 for arm_unknown_linux)

    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

Good news is it appears to be an ARM issue rather than an Elm issue.

[Mads Flensted-Urech]

I get this one too in 7.4.2 (64bit on Intel). Googling this changeset shows up. Will have to check why the RTS is not configured for multithreading, if I understand the error correctly.

[Mads Flensted-Urech]

Ok - found it. You need to build with -threaded option to ghc:

cabal build --ghc-option=-threaded

In researching this I fond it strange that I could not search for either setNumCapabilities or getNumProcessors on hoogle to found the module they belonged to. Here Elm doc's are much better.

Anyway found the solution here

[Alex Shroyer]

Thanks Mads, you are awesome.  Quick question, should this command:

cabal build --ghc-option=-threaded 

be executed in my new (dev branch checked out) Elm/ directory?

[Mads Flensted-Urech]

You are welcome. Yes - here is the full list of "install" commands that currently work for me (using ghc 7.4) when I start from a clean setup:

cd Elm

cabal update

cabal install --only-dependencies

cabal configure

cabal build --ghc-option=-threaded

cabal install

[Evan Czaplicki]

Hmm, I think I am responsible for this. I took off the -O2 and -threaded flags from the .cabal file to try to bring down install times. Perhaps that was misguided in the first place. I'll add them back and ping this thread when it's added. Would you mind trying to install again after that to see if this is resolved?

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[Mads Flensted-Urech]

No problem, can easily re-test

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[Alex Shroyer]

I'll definitely re-install to test, Evan.  I want to play with markdown and also get the new and improved compiler error messages. :)

[Evan Czaplicki]

Okay, it should be updated. Let me know if the issue is resolved!

Unfortunately though, I decided to wait until later for the markdown interpolation, so it is "turned off" in dev at the moment. I was thinking of making a separate branch for it, but I did not do that yet.

On Fri, Dec 13, 2013 at 11:00 AM, Alex Shroyer <ashr...@gmail.com> wrote:

I'll definitely re-install to test, Evan.  I want to play with markdown and also get the new and improved compiler error messages. :)

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[Mads Flensted-Urech]

Yes - now it works with just "cabal build"

With regards to ghc version, is it you target that Elm should compile on both 7.4 and 7.6 ?

[Alex Shroyer]

Working for me on ARM as well.  Thank you Evan and Mads!

[Evan Czaplicki]

Mads, not explicitly, but I'd like to be as permissive as possible. My main goal is to minimize the amount of install crap that people have to go through (cabal hell, etc.) and I don't think I need any 7.6 features. I stopped using multiway ifs because of this.

Glad it's working!