array: add S.size

[davidchambers]

This is equivalent to Haskell's length function.

I quite often find myself using S.prop('length') as Array a -> Integer; it will be convenient to be able to use S.length S.size in these situations instead. :)

[gabejohnson]

As I mentioned in #413 I think size or count would be a more appropriate name given that not all Foldable structures have a "length" (e.g. sets and trees).

[davidchambers]

Thanks for raising the question of naming, Gabe. I took the name from Haskell (and Ramda), but we're not forced to follow Haskell's lead.

Let's indicate our preferences via emoji:

• 👍 = length
• 😄 = size
• ❤️ = count

[davidchambers]

@Avaq? @safareli? @scott-christopher? Do you have preferences?

[Avaq]

Oh - I had cast my vote using a mobile app. Guess it didn't work. I prefer size, because JavaScript has conditioned me to treat length like a Number.

[davidchambers]

Now that #413 has been merged we're able to include tests for lists. :)

[safareli]

the function could also be moved in s-type-classes

[davidchambers]

Good point, Irakli! It would be nice to decide upon a rule we can apply to tell us whether a particular function warrants inclusion in sanctuary-type-classes. Does anyone have a suggestion?

[safareli]

If a function is polymorphic and it's input have some algebraic constraints, maybe.

[gabejohnson]

It's interesting that given the definition of reduce for Pair, size(Pair(1, 2)) === 1.

Though the "size" of a Pair is encoded in the type, so it really doesn't matter.

[davidchambers]

I like your suggestion, Irakli. :)

I will open a pull request to define size in sanctuary-type-classes. There are no doubt some other S functions whose implementations should move to Z too.

[davidchambers]

Superseded by sanctuary-js/sanctuary-type-classes#61