fixadd

Section: Allegro manual (3)
Updated: version 4.2.2
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NAME

fixadd - Safe function to add fixed point numbers clamping overflow. Allegro game programming library.  

SYNOPSIS

#include <allegro.h>

fixed fixadd(fixed x, fixed y);  

DESCRIPTION

Although fixed point numbers can be added with the normal '+' integer operator, that doesn't provide any protection against overflow. If overflow is a problem, you should use this function instead. It is slower than using integer operators, but if an overflow occurs it will set `errno' and clamp the result, rather than just letting it wrap. Example: 

   fixed result;
   /* This will put 5035 into `result'. */
   result = fixadd(itofix(5000), itofix(35));
   /* Sets `errno' and puts -32768 into `result'. */
   result = fixadd(itofix(-31000), itofix(-3000));
   ASSERT(!errno); /* This will fail. */
 

RETURN VALUE

Returns the clamped result of adding `x' to `y', setting `errno' to ERANGE if there was an overflow.

 

SEE ALSO

fixsub(3), fixmul(3), fixdiv(3)