Some extra functions, fixes #20

[hdgarrood]

Some of this is already in purescript-posets, but it could potentially be more helpful to have it in Prelude.

[garyb]

I wonder if we'd be better off with breaking some of these out into libraries like purescript-ordering for Data.Ord, etc instead. Adding these to the Prelude as they are are going to cause some problems: min, max, and abs are already defined in purescript-math, succ and pred will conflict with purescript-enums.

Also, this is just a personal opinion, but I think keeping the Prelude compact is something we should try to hold on to.

[hdgarrood]

Ok, makes sense.

Exporting generalised versions of functions with the same name as Math functions doesn't both me very much though, particularly since I find I use integers far more often than floating point numbers, and nothing in Math works for Int. If we have generalised min, max, and abs, is there a reason to use the Math versions at all?

[sharkdp]

I haven't looked at all the new functions in this PR, but I would strongly vote in favor of generalizing max and min!

Exporting generalised versions of functions with the same name as Math functions doesn't both me very much though, particularly since I find I use integers far more often than floating point numbers, and nothing in Math works for Int.

👍
It seems a shame that we have no min/max :: Int -> Int -> Int which we would get for free.

If we have generalised min, max, and abs, is there a reason to use the Math versions at all?

Related: purescript-deprecated/purescript-math#8

[hdgarrood]

Since I finally got around to publishing purescript-posets (now purescript-orders, given that we decided Ord should be a total ordering), I think we can close this.