1#define _GNU_SOURCE 2#include "libc.h" 3#include <math.h> 4#include <stdint.h> 5 6double exp10(double x) { 7 static const double p10[] = {1e-15, 1e-14, 1e-13, 1e-12, 1e-11, 1e-10, 1e-9, 1e-8, 8 1e-7, 1e-6, 1e-5, 1e-4, 1e-3, 1e-2, 1e-1, 1, 9 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 10 1e9, 1e10, 1e11, 1e12, 1e13, 1e14, 1e15}; 11 double n, y = modf(x, &n); 12 union { 13 double f; 14 uint64_t i; 15 } u = {n}; 16 /* fabs(n) < 16 without raising invalid on nan */ 17 if ((u.i >> 52 & 0x7ff) < 0x3ff + 4) { 18 if (!y) 19 return p10[(int)n + 15]; 20 y = exp2(3.32192809488736234787031942948939 * y); 21 return y * p10[(int)n + 15]; 22 } 23 return pow(10.0, x); 24} 25 26weak_alias(exp10, pow10); 27