Re: [Caml-list] kprintf with user formatters

[Markus Mottl <markus@oefai.at>]

On Fri, 16 Jul 2004, Pierre Weis wrote:
> I don't know of any way to safely prevent the arguments of printf from
> being converted to string when interpreting the format.

This would probably require some changes in the implementation of
Printf/Format.

> Since you have a if then else, the ``???'' expression should have
> exactly the same type as the ``then kfprintf ...'' expression. Hence
> the simplest way to do so is to have another kfprintf invocation with
> the same format. Evidently you want to redirect the output of this
> invocation to /dev/null (I mean you do not want to see its output).

Not only this: I want to prevent any computations associated with
generating output strings.

> The best way to do so is not to redefine a specialized version of
> printf, it is simply to define a specialized pretty printer that would
> behave as you want and then to specialize fprintf with it:
> 
> let null_formatter =
>   let null_out s idx len = () in
>   let null_flush = ignore in
>   Format.make_formatter null_out null_flush;;

This would surely ignore any output, but "null_out" would still be called
with superfluously generated strings.

Anyway, the argument-eating function that makes use of "Obj.magic"
works for me so my problem is solved.

Regards,
Markus

-- 
Markus Mottl          http://www.oefai.at/~markus          markus@oefai.at

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