Subversion Repositories planix.SVN

#include <errno.h>
#include <float.h>
#include <math.h>

static  long    tab[] =
{
        1L, 10L, 100L, 1000L, 10000L,
        100000L, 1000000L, 10000000L
};

double
pow10(int n)
{
        int m;

        if(n > DBL_MAX_10_EXP){
                errno = ERANGE;
                return HUGE_VAL;
        }
        if(n < DBL_MIN_10_EXP){
                errno = ERANGE;
                return 0.0;
        }
        if(n < 0)
                return 1/pow10(-n);
        if(n < sizeof(tab)/sizeof(tab[0]))
                return tab[n];
        m = n/2;
        return pow10(m) * pow10(n-m);
}