opendarwin man page for fixadd

fixadd(3alleg4) 						  Allegro manual						   fixadd(3alleg4)

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(3alleg4), fixmul(3alleg4), fixdiv(3alleg4)

Allegro 							   version 4.4.2						   fixadd(3alleg4)