Re: [avr-gcc-list] Operation problem

[Paulo Marques]

Gerard Marull Paretas wrote:
> Hello.

Hi,

> When I try to execute this line:
>
> currentsong.length=(currentsong.frames * currentsong.samples_per_frame) 
> / currentsong.samples_per_sec;
>
> currentsong.length gets no result. However, doing these operations step 
> by step produce the expected results:
>
> currentsong.length=currentsong.frames;
> currentsong.length*=currentsong.samples_per_frame;
> currentsong.length/=currentsong.samples_per_sec;
>
> The second method requires currentsong.length to be a long int 
> (uint32_t), because the multiplication of currentsong.frames by 
> currentsong.samples_per_frame does not fit on an uint16_t.

I think you just answered your own question: if all the variables 
involved are uint16_t, then that is the precision used for all he 
expression and it will overflow on the multiplication.

--
Paulo Marques
Software Development Department - Grupo PIE, S.A.
Phone: +351 252 290600, Fax: +351 252 290601
Web: www.grupopie.com

"A tautology is a thing which is tautological."