Discussion for proposal 2015-003

[JohnReppy]

This issue is for discussion of proposal 2015-003 (Additional operations on sequences).

[rossberg-old]

All good suggestions. A couple of additional ones:

• For completeness, I think toList and toVector functions should also be added to ArraySlice, VectorSlice, ARRAY_MONO_SLICE and VECTOR_MONO_SLICE.
• One sequence functional I tend to miss more often than most of what's proposed here is appr, which is like app but iterates right-to-left. I suggest adding it to all sequence signatures (arrays, vectors, slices, lists, list pairs), along with the respective appri.
• ListPair is also strangely lacking find (and findi), which I have missed in the past.

[JohnReppy]

I added mapUnzip and mapUnzipi functions to the ListPair description.

I will also update the proposal to include Andreas' proposals.

[JohnReppy]

I have added the find and findi functions to ListPair as proposed by Andreas. I'll make the other additions when I have some more time.

[MatthewFluet]

The toList and toVector functions to the Slice/SLICE modules make sense.

A concern with appr and appri is that it begs the question of why not *r variants of all of the other list traversal functions: map, filter, all, exists, ....

[rossberg]

Because the other ones are typically applied to pure functions, where the order shouldn't matter. The app functions, however, are only intended for side effects, where order matters a lot.

[JohnReppy]

With respect to the proposed appr and appri functions, does it make sense to also define
appl and appli as aliases for app and appi? This addition would preserve consistency with the foldl/foldr etc.

[rossberg-old]

Hm, I don't have much love for aliases personally. And without actually removing app it doesn't really create any symmetry either.