λ Lessons

#1

Post by lelf » Fri, Aug 08, 2014, 11:43 PM UTC

λ Lessons
stevekrouse.github.io

Re: λ Lessons

#2

Post by nwhitehead » Sat, Aug 09, 2014, 1:23 AM UTC

Doesn't appear to work on ipad.

Re: λ Lessons

#3

Post by paf31 » Sat, Aug 09, 2014, 1:29 AM UTC

Very nice. It took me a while to realize that array literals aren't supported, but once I did that I was able to write concatMap and watch it being evaluated.

A couple of points:

- If there is a syntax error, the box just turns red. It would be nice to see what the issue is.

- You could probably make it clearer that it's possible to execute arbitrary expressions, by editing the map term, for example.

Re: λ Lessons

#4

Post by TrainedMonkey » Sat, Aug 09, 2014, 1:35 AM UTC

Neat, however it feel clunky. Few things that bugged me:

1. Clear does not work. Firefox 22.0, private mode.

2. Clicking to expand gets tedious fast. Adding shortcut like space would be nice.

3. No syntax highlighting on function editor, also lists could use some colors.

Re: λ Lessons

#5

Post by gravity13 » Sat, Aug 09, 2014, 1:50 AM UTC

Really awesome stuff JP and Steve! I've been having similar ideas about the subject myself :)

Re: λ Lessons

#6

Post by fyolnish » Sat, Aug 09, 2014, 2:26 AM UTC

Would love to play with this, but clicking the expansions crashes Safari on my machine

Re: λ Lessons

#7

Post by mrcactu5 » Sat, Aug 09, 2014, 3:01 AM UTC

there is a typo

  This document implements a small, dyanmically-typed, 
  subset of Haskell that includes integers, lists, functions,      
  pattern matching and recursion.

Also, Haskell is strictly typed... but most of us aren't ready for that anyway :-P

Re: λ Lessons

#8

Post by justinpombrio » Sat, Aug 09, 2014, 4:53 AM UTC

TrainedMonkey wrote: post #4

Neat, however it feel clunky. Few things that bugged me: 1. Clear does not work. Firefox 22.0, private mode. 2. Clicking to expand gets tedious fast. Adding shortcut like space would be nice. 3. No syntax highlighting on function editor, also lists could use some colors.

4. Hitting 'enter' after editing only sometimes gets you out of editing mode; seemingly only if your expression is well-formed?

5. 'Clear' clears some lines but not all. It usually seems to clear all but the top two lines for me.

Chrome v.36 in Ubuntu

Re: λ Lessons

#9

Post by justinpombrio » Sat, Aug 09, 2014, 5:11 AM UTC

This will be a cool demo once the kinks get worked out. It lets you see first-hand that you can choose which redex to beta-expand first. Haskell is an excellent choice for this because -- unlike almost every other language -- it does not matter the order you evaluate subexpressions in. I feel like this could be useful to show someone when teaching them to program.

The language in the function editor on the right looks like Haskell. I'm confused as to what the language you run is supposed to be, though. It doesn't seem to have Haskell syntax or semantics. The lists aren't comma-separated, and the main expression seems to require parenthesis? And what is this program doing?

    (map (plus 1) [12])
    (( 1) : (map (plus 1) [2]))
    (( 1) : (( 2) : (map (plus 1) [])))
    (( 1) : (( 2) : []))
    (( 1) : [( 2)])
    [( 1)( 2)]

vs. in Haskell

    Prelude> map (+ 1) [1, 2]
    [2,3]

Re: λ Lessons

#10

Post by janpaul123 » Sat, Aug 09, 2014, 5:27 AM UTC

mrcactu5 wrote: post #7

there is a typo This document implements a small, dyanmically-typed, subset of Haskell that includes integers, lists, functions, pattern matching and recursion. Also, Haskell is strictly typed... but most of us aren't ready for that anyway :-P

Thanks, fixed in https://github.com/stevekrouse/hs.js/commit/9882af6312f93a29...