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From: Pierre Weis <pierre.weis@inria.fr>
Message-Id: <200207121241.OAA24723@pauillac.inria.fr>
Subject: Re: [Caml-list] printf hook
In-Reply-To: <004001c2298d$de86f7f0$3700a8c0@warp> from Nicolas Cannasse at "Jul 12, 102 12:21:20 pm"
To: warplayer@free.fr (Nicolas Cannasse)
Date: Fri, 12 Jul 2002 14:41:11 +0200 (MET DST)
Cc: Jean-Christophe.Filliatre@lri.fr, caml-list@inria.fr
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> I just found something quite funny :
> 
> let print x =
>     printf "BEGIN";
>     printf x;
>     flush stdout
> 
> print "test";;
> print "%d" 10; (** TOO MUCH ARGS **)

This is normal, isn't it ?

> ============
> 
> let print x =
>     printf "BEGIN";
>     let r = printf x in
>     flush stdout;
>     r
> 
> print "test";
> print "%d" 10; (** WORKING **)

This is also perfectly regular: your code

let print x =
  printf "BEGIN";
  let r = printf x in
  flush stdout;
  r

is functionally equivalent to

let print x =
  let r = printf x in
  r

which is again functionally equivalent to

let print x = printf x

which is again equivalent to

let print = printf

The type checker gives an hint on that fact, since print is reported
having the same type as printf:

        Objective Caml version 3.04+15 (2002-06-18)

#open Printf;;
# let print x =
  printf "BEGIN";
  let r = printf x in
  flush stdout;
  r;;
val print : ('a, out_channel, unit) format -> 'a = <fun>
# printf;;
- : ('a, out_channel, unit) format -> 'a = <fun>

Pierre Weis

INRIA, Projet Cristal, Pierre.Weis@inria.fr, http://pauillac.inria.fr/~weis/


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