Result Containers

[JSuder-xx]

Containers meet Result. This includes a few of the userful *M functions renamed for the Elm community. In all of the examples below the m with constraint Monad m is Result.

• Result.foldl is foldM where the foldable List.
• Result.foldlArray is foldM where the foldable Array.
• Result.filterList is filterM where the container is List. Please note that Result.filter was already taken.
• Result.filterArray is filterM where the container is Array.
• Result.map2 is zipWithM where the container is List.
• Result.map2Array is zipWithM where the container is Array.

[miniBill]

Tentative +1 to the map2s.

+1 to the foldl (#60).

I'm not sure I like the filters to be honest?

Maybe this is better off split?

[JSuder-xx]

@miniBill I agree with your assessment completely 😄. I actually opened this to add the foldl (foldM), then thought the map2 would be a nice, simple, and useful addition, and then finally added the filters only for "completeness" with the Monadic generalizations on lists (*M functions), but

• the name collision with the existing Result.filter is confusing and decreases ease of Api learning and navigation.
• the filters seem less useful and I don't think they meet the bar for usefulness of inclusion in a core library.

I see you have #60 for the case that motivated this PR.

What would you prefer I do?

• Close this and let Add Result.Extra.combineFoldl #60 take care of this concern.
• Remove the filters
• Something else

[miniBill]

My preference would be:

1. open a PR for foldls
2. open a PR for map2s
3. open a PR for filters
4. close this

So we can discuss them separately