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Date: Tue, 8 Jun 2010 13:28:44 +0200
Message-ID: <AANLkTikI4-YKT7A3AaNoippzvyAZBRU-HlhaGAh6QwrC@mail.gmail.com>
Subject: Re: [Caml-list] Converting variants with only constant constructors 
	to integers
From: Kaustuv Chaudhuri <kaustuv.chaudhuri@inria.fr>
To: caml-list caml-list <caml-list@yquem.inria.fr>
Cc: bluestorm <bluestorm.dylc@gmail.com>
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X-Spam: no; 0.00; variants:01 constructors:01 integers:01 foo:01 integers:01 foo:01 compiler:01 segfaults:01 ocaml:01 val:01 4.2:98 caml-list:01 constructor:01 int:01 int:01 

2010/6/7 bluestorm <bluestorm.dylc@gmail.com>:
> If you were, for example, to change your definition of "foo" (in a way not
> always representable as integers, such as adding a constructor with
> parameters), int_of_foo would become incorrect. The compiler wouldn't warn
> you, and you could get pretty bad failures (segfaults). You're on your own.

%identity will never cause a seg fault.

  % ocaml
          Objective Caml version 3.12.0+dev25 (2010-05-20)

  # external intify : 'a -> int = "%identity" ;;
  external intify : 'a -> int = "%identity"
  # intify "hello, world" ;;
  - : int = 70165942419644
  # intify [10; 20] ;;
  - : int = 70165942402044
  # intify 4.2 ;;
  - : int = 70165942392140
  # intify 322L ;;
  - : int = 70165942379652
  # intify 322L ;;
  - : int = 70165942369800

Obviosly if you write code that depends on such values, then your code
is most likely broken:

  # let x = [10; 20] ;;
  val x : int list = [10; 20]
  # intify x ;;
  - : int = 70165942003824
  # Gc.compact () ;;
  - : unit = ()
  # intify x ;;
  - : int = 70165941843960

-- Kaustuv