1 #include <lib9.h> 2 3 /* 4 * this table might overflow 127-bit exponent representations. 5 * in that case, truncate it after 1.0e38. 6 * it is important to get all one can from this 7 * routine since it is used in atof to scale numbers. 8 * the presumption is that C converts fp numbers better 9 * than multipication of lower powers of 10. 10 */ 11 12 static 13 double tab[] = 14 { 15 1.0e0, 1.0e1, 1.0e2, 1.0e3, 1.0e4, 1.0e5, 1.0e6, 1.0e7, 1.0e8, 1.0e9, 16 1.0e10,1.0e11,1.0e12,1.0e13,1.0e14,1.0e15,1.0e16,1.0e17,1.0e18,1.0e19, 17 1.0e20,1.0e21,1.0e22,1.0e23,1.0e24,1.0e25,1.0e26,1.0e27,1.0e28,1.0e29, 18 1.0e30,1.0e31,1.0e32,1.0e33,1.0e34,1.0e35,1.0e36,1.0e37,1.0e38,1.0e39, 19 1.0e40,1.0e41,1.0e42,1.0e43,1.0e44,1.0e45,1.0e46,1.0e47,1.0e48,1.0e49, 20 1.0e50,1.0e51,1.0e52,1.0e53,1.0e54,1.0e55,1.0e56,1.0e57,1.0e58,1.0e59, 21 1.0e60,1.0e61,1.0e62,1.0e63,1.0e64,1.0e65,1.0e66,1.0e67,1.0e68,1.0e69, 22 }; 23 24 double 25 pow10(int n) 26 { 27 int m; 28 29 if(n < 0) { 30 n = -n; 31 if(n < sizeof(tab)/sizeof(tab[0])) 32 return 1/tab[n]; 33 m = n/2; 34 return pow10(-m) * pow10(m-n); 35 } 36 if(n < sizeof(tab)/sizeof(tab[0])) 37 return tab[n]; 38 m = n/2; 39 return pow10(m) * pow10(n-m); 40 } 41