Re: round not in math.h?

Wolfgang Jansen <[email protected]> wrote:
	I have to improve the program splitter as follows:
	
	  EIF_REAL_64 x;
	  EIF_INTEGER_64 n;
	
	  int sign = (x < 0 ? -1 : 1);
	  x = fabs(x)+0.5;
	  if (x<ULLONG_MAX) {
	    n = x;
	    x = n;
	  }
	  if (sign<0)  x = -x;
	
There is a much simpler and more portable way.
There is a round() function in C99; there wasn't in C89.
But C89 does have floor() and ceil(), and the value of
round() must always be equal to one of those.  And indeed
we can use the "add a half with same sign then chop back
towards zero" technique.

So
    #include <math.h>

    double round64(double x) {
	return x < 0.0 ? ceil(x-0.5) : floor(x+0.5);
    }

does the job easily.