Re: [Caml-list] printf hook

[Pierre Weis <pierre.weis@inria.fr>]

> 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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