Re: [Caml-list] getting the type of a polymorphic data ?

[Diego Olivier Fernandez Pons <Diego.FERNANDEZ_PONS@etu.upmc.fr>]

    Bonjour,

> Not quite.
>
> # Hashtbl.hash 0x4000_0000;;
> - : int = 0
> # Hashtbl.hash 0;;
> - : int = 0

Yes but

# let x = 0x4000_0000;;
val x : int = -1073741824

If the only case of collision is due to modulo 2^31 then it is - at
least for me - reasonable since the user is supposed to have a minimal
knowledge of computer science. And Caml allows him to check with
max_int / min_int for overflows.

(* obviously doesn't typecheck, just for example *)

let hashable = function x ->
  x < max_int && x > min_int && Obj.is_int (Obj.repr x)

hashable x, y => hash injective




        Diego Olivier

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