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Date: Fri, 9 Oct 2009 07:25:41 +0200 (SAST)
Subject: Why type inference fails in this code
From: rouanvd@softwarerealisations.com
To: caml-list@yquem.inria.fr
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X-Spam: no; 0.00; inference:01 compiler:01 ocaml:01 inference:01 messes:01 foo:01 haskell:01 infers:01 foo:01 workarounds:01 int:01 int:01 string:02 string:02 workaround:03 

Hi everyone

I am trying to decide what language to use to write a compiler for my own
programming language.
I am leaning towards OCaml, but I don’t want the type system or debugging
tools to be a problem.

I found this code snippet in a post and was wondering why the type
inference messes up with
The following code:

======================================================
type t = MyInt of int | MyFloat of float | MyString of string ;;

let foo printerf = function
  | MyInt i -> printerf string_of_int i
  | MyFloat x -> printerf string_of_float x
  | MyString s -> printerf (fun x -> x) s
;;
======================================================

I have done the same thing in Haskell and it correctly infers the type of
foo.

I read that there are lots of workarounds for the above code snippet, but
I would like to
Know why this code fails and what is the best workaround for this type of
code.

Regards
Rouan.