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