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Comment by nemo1618 | Hacker News Reader

Nice, but I was hoping for something like:

  slice :: Int{1..} -> [a] -> [[a]]
  slice n l =
    splitAt n l & \(a, b) -> a : slice n b

I don't think this is possible in Haskell. Is there a language that supports this sort of syntax?

(Also, what's up with that &? It doesn't seem to be a Prelude operator.)

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Liquid Haskell might be what you are looking for: http://goto.ucsd.edu/~rjhala/papers/real_world_liquid.pdf

An example from that paper:

    type Nat = {v:Int | 0 <=v }
    type Pos = {v:Int | 0 < v }
    div :: Nat -> d:Pos -> {v:Nat | v <= n}

The ATS programming language (http://www.ats-lang.org) is more ML-like than Haskell-like but can have ranged integer types. Something like:

    fun slice {n:int | n >= 1} (a:int n, b:list)

Regarding &: https://www.fpcomplete.com/hoogle?q=%26&env=ghc-7.8-stable-1...

If it's from lens, then it's "the flipped version of ($)".

There is a similar explanation if you search google for `haskell ampersand`[0]

[0] http://qerub.se/ampersand

What's the difference (&) and reverse function composition?

Precisely the difference between function application and function composition.

Dependently typed languages like DML, Epigram, ATS, Coq, Agda or Idris supports these kind of types. Unfortunately it quickly becomes difficult to work with this kind of typing when you introduce more complex properties.

> Also, what's up with that &? It doesn't seem to be a Prelude operator.

It's now in [Data.Function of "base"](http://hackage.haskell.org/package/base-4.8.0.0/docs/Data-Fu...) and hence in ["base-prelude"](http://hackage.haskell.org/package/base-prelude).

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