Re: list composition functions

[Alain Frisch <frisch@clipper.ens.fr>]

On 16 Oct 2000, Julian Assange wrote:
> Imagine you have the follow three functions,
> 
> let mirror x = [x;x]
> let plus1 x = [x+1]
> let none x = []
> 
> I'm trying to define an operator (>>) that will then operate like so
> 
> (mirror >> mirror >> plus1) [1]
> 
> [2;2;2;2]

You could try something like:

let build_transformer f x =
    List.concat (List.map f x)

let (>>) t1 t2 x =
    t1 (t2 x)

let mirror = build_transformer (fun x -> [x;x])
let plus1  = build_transformer (fun x -> [x+1])
let none   = build_transformer (fun x -> [])


(mirror and none are not generalized since their definition
is expansive)


-- 
  Alain Frisch