No fold/reduce functions available in codeworld?

[maspotts]

Shared Program: https://code.world/#Pss8gW_0yQqOj_L9wLm0QDQ

Description

I'm trying to show my kid how to replace this pattern:

picture1 & picture2 & picture2

with (the codeworld equivalent of) this pattern:

foldl1 (&) listOfPictures

but I can't find foldl (or foldl1, foldl', foldr, etc.) in codeworld:

Variable not in scope:
      foldl :: ((Number, Number) -> Number, Number, [Number]) -> t

and I also can't import Data.List:

Could not find module Data.List

Is this possible, or am I trying to do something that's forbidden within codeworld?

[cdsmith]

There is no general fold in CodeWorld's educational dialect. There are specific folds, including pictures, which does what you want. Other than that, I would recommend writing a recursive function.

If you want the Haskell base, you should use http://code.world/haskell, and import the CodeWorld module. That will get you a standard Haskell environment.

[bbarker]

Just to elaborate slightly, I think the lack of folds is due to type classes not being exposed in the CodeWorld language.

[maspotts]

Thanks so much for that explanation (and the detail). I definitely want to stay within codeworld because of the Picture type; I did try to step out (code.world/haskell) but I couldn't import Extras.Cw (due to it being hidden). I guess my ideal scenario would be a way to use pure haskell but have the whole of codeworld base + extras available; is that possible?

But for now the pictures function (which I had totally missed - doh!) is a great solution.

Thanks again,

Mike

[cdsmith]

@maspotts Yes, http://code.world links with the codeworld-base package, while http://code.world/haskell links with codeworld-api and hides codeworld-base. The ideal situation would be that everything in codeworld-base is also available in either base or codeworld-api... but you are right that the Extras.* modules do not yet exist in codeworld-api. If anyone wants to complete that port, I would be happy to review the pull request. I agree with the change in principle, but it's not on my list of changes I'll be making soon.

[cdsmith]

You can also see #1477 for some discussion of using base from the CodeWorld educational dialect. It is possible, but it's complex enough that I definitely wouldn't recommend it for students. But if you want to use it to implement some kind of framework to provide to your students to import by hash, that would be quite reasonable.

[maspotts]

Thanks: funnily enough #1477 was also from me, before I discovered the github repo, so thanks for pointing out all those replies to me! :). I'm finding codeworld (in the browser) ideal for onboarding my mathematically inclined 7th grader to coding; he's using it to code up his extra credit algebra homework currently; but it would certainly be awesome to be able to access the codeworld environment (especially Picture) from codeworld/haskell so as to be able to to gently transition him to pure haskell (and perhaps then purescript) at some point. Being able to import all of codeworld-base (including extras) would be perfect. (Naively my goal would be to enable him to evolve to writing idiomatic haskell but still have access to all the codeworld functions he's used to.)

Mike

[cdsmith]

Picture is already available in http://code.world/haskell; just import the CodeWorld module.

The Extras.* modules are not.

[maspotts]

Yes I found that: thanks! Unfortunately he needed a bigger coordinate grid than the default (10,10) so we had to use CustomGraphed() from Extras.Cw, which means we couldn't use code.world.haskell for that because we couldn't import Extras.Cw .

[cdsmith]

I've filed a more targeted issue for Extras not being available in codeworld-api. I think everything else here has been resolved, so I'll close this. Please reopen if you disagree.

[maspotts]

Thanks!