Re: [Sbcl-help] Re: Problem with alien-funcall and float arg

[Richard R. <rr...@ms...>]

I know there is a method to the madness.

Thanks
Richard

On Thu, 19 Jan 2006 er...@on... wrote:

> Richard Ray <rr...@ms...> writes:
>
>>>>>> (alien-funcall (extern-alien "TIFFSetField"
>>>>>>                              (function int system-area-pointer int float))
>>>>>>                tf 282 200.0)
>>
>> But this works
>>
>> (alien-funcall (extern-alien "TIFFSetField"
>>                               (function int system-area-pointer int double))
>>                 tf 282 200.0d0)
>>
>> But the parameter is defined as a float.
>
> This is because float is promoted to double in the variable-length
> part of variable-length argument lists.  See the comp.lang.C FAQ at
> http://c-faq.com/varargs/float.html
>
> Similarly char and short are promoted to int.
>
>> Also the parameter must be read with TIFFGetField using a (* float).
>> Using a (* double) does not cause an error but the returned value is
>> wrong.
>
> In this case the argument is a pointer type and the default argument
> promotions does not apply.
>
> -Erik
> -- 
> /d{def}def/m{mul}d/a{add}d/q{repeat}d/y 1 d 300{/x 1 d 600{/c x 600 div 4 m 2
> sub d/z y 300 div 2 m 1 sub d/r 0 d/i 0 d/t 0 d{t 1 le{/n r r m i i m sub c a
> d/b 2 r m i m z a d/r n d/i b d r r m i i m a 16 gt{exit}if} {exit}ifelse/t t
> .01 a d}loop t setgray x y moveto 1 1 rlineto stroke/x x 1 a d}q /y y 1 a d}q
>
>
>
> -------------------------------------------------------
> This SF.net email is sponsored by: Splunk Inc. Do you grep through log files
> for problems?  Stop!  Download the new AJAX search engine that makes
> searching your log files as easy as surfing the  web.  DOWNLOAD SPLUNK!
> http://sel.as-us.falkag.net/sel?cmd=lnk&kid=103432&bid=230486&dat=121642
> _______________________________________________
> Sbcl-help mailing list
> Sbc...@li...
> https://lists.sourceforge.net/lists/listinfo/sbcl-help
>