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To: caml-list@inria.fr
Subject: Re: [Caml-list] Type inference problem
References: <20010628172348.A24964@boblycat.com>
From: Remi VANICAT <vanicat@labri.u-bordeaux.fr>
Date: 28 Jun 2001 17:40:20 +0200
In-Reply-To: <20010628172348.A24964@boblycat.com>
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Vasilij Karpow <malc@boblycat.com> writes:

> Can anyone explain why O'Caml specializes the following:
> 
> let simple ?fn list =
>   let fn = match fn with
>   | Some fn -> fn
>   | None -> fun t -> t in
>   let rec print = function
>     | [] -> ()
>     | x :: xs -> print_endline (fn x); print xs
>   in
>   print list
> 
> let _ =
>   simple ["1"];
>   simple ~fn:(fun i -> string_of_int i) [1]
> 
> 
> to: val simple : ?fn:(string -> string) -> string list -> unit

it's easy. If the value was polymorphic, you would be authorized to
write :

simple [1; 2; 3; 4; 5]

which is unsound.


-- 
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat
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