listfunctionocamlstrong-typingvariants

Variants and lists in Ocaml

Is it possible to define a list using variants (or something else) which would contain integers and functions simultaneously? I am particularly interested in mixing functions and some other type in a list.

Analogously is it possible to create a function which could return either a number or a function? Please if possible give code examples of both cases.

Solution 
  • type my_elt = 
  | Null
  | Int of int
  | Fun1 of (int-> unit)
  | Fun2 of (int-> int)

let eval a =function
  | Fun1 f -> f a;Null
  | Fun2 f -> Int (f a)
  |  _     -> Null

let leval a l = List.map (fun elt -> eval a elt ) l  
;;

    Test :

    let l=[Int 2;Fun1 (Printf.printf "%d");Fun2 ((+)2) ]
# leval 2 l;;
2- : my_elt list = [Null; Null; Int 4]