4 ms·

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

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.)

ics 11y ago
Regarding &: https://www.fpcomplete.com/hoogle?q=%26&env=ghc-7.8-stable-14.09 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 ($)".
- mijoharas 11y ago
  There is a similar explanation if you search google for `haskell ampersand`[0] [0] http://qerub.se/ampersand http://qerub.se/ampersand
- CMCDragonkai 11y ago
  What's the difference (&) and reverse function composition?
  - dllthomas 11y ago
    Precisely the difference between function application and function composition.
typish 11y ago
Liquid Haskell might be what you are looking for: http://goto.ucsd.edu/~rjhala/papers/real_world_liquid.pdf 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 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)
seanwilson 11y ago
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.
nikita-volkov 11y ago
> 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-Function.html#v:-38- 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 http://hackage.haskell.org/package/base-prelude).

ics 11y ago

Regarding &: https://www.fpcomplete.com/hoogle?q=%26&env=ghc-7.8-stable-14.09 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 ($)".

mijoharas 11y ago
There is a similar explanation if you search google for `haskell ampersand`[0] [0] http://qerub.se/ampersand http://qerub.se/ampersand
CMCDragonkai 11y ago
What's the difference (&) and reverse function composition?
- dllthomas 11y ago
  Precisely the difference between function application and function composition.

typish 11y ago

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

seanwilson 11y ago

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.

nikita-volkov 11y ago

> 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-Function.html#v:-38- 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 http://hackage.haskell.org/package/base-prelude).