On 11/6/07, Nicolas Pouillard <nicolas.pouillard@gmail.com> wrote:
> Excerpts from tmp123's message of Tue Nov 06 18:05:48 +0100 2007:
> > Hello,
> >
> > In order to implement a function that prints log messages only, by
> > example, if a boolean flag is true, and does nothing elsewhere, I've
> > been reading the (long) post sequence "kprintf with user formatters"
> > (2004 Jun 30).
> >
> > In this context, "does nothing" means not convert parameters to text nor
> > evaluate them.
>
> Have a look to the Printf.ifprintf [1] function, it does exactly what you want.
>
> Regards,
>
Actually it doesn't:

   log (lazy (Printf.printf "%s" (awfully_long_computation ())))

when log_val is false (or sylvain's solution, which I prefer), will
not behave like

   Printf.ifprinf "%s" (awfully_long_computation ())

(it won't evaluate its arguments).

Till
-- 
http://till-varoquaux.blogspot.com/