The R Project SVN R

#include "f2c.h"

#ifdef KR_headers
double pow_di(ap, bp) doublereal *ap; integer *bp;
#else
double pow_di(doublereal *ap, integer *bp)
#endif
{
double pow, x;
integer n;
unsigned long u;

pow = 1;
x = *ap;
n = *bp;

if(n != 0)
    {
    if(n < 0)
        {
        n = -n;
        x = 1/x;
        }
    for(u = n; ; )
        {
        if(u & 01)
            pow *= x;
        if(u >>= 1)
            x *= x;
        else
            break;
        }
    }
return(pow);
}