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	pow10.c - 9base - revived minimalist port of Plan 9 userland to Unix
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	pow10.c (1301B)
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	1 /* Copyright (c) 2002-2006 Lucent Technologies; see LICENSE */
	2 #include <stdarg.h>
	3 #include <string.h>
	4 #include "plan9.h"
	5 #include "fmt.h"
	6 #include "fmtdef.h"
	7
	8 /*
	9 * this table might overflow 127-bit exponent representations.
	10 * in that case, truncate it after 1.0e38.
	11 * it is important to get all one can from this
	12 * routine since it is used in atof to scale numbers.
	13 * the presumption is that C converts fp numbers better
	14 * than multipication of lower powers of 10.
	15 */
	16
	17 static
	18 double tab[] =
	19 {
	20 1.0e0, 1.0e1, 1.0e2, 1.0e3, 1.0e4, 1.0e5, 1.0e6, 1.0e7, 1.0e8, 1…
	21 1.0e10,1.0e11,1.0e12,1.0e13,1.0e14,1.0e15,1.0e16,1.0e17,1.0e18,1…
	22 1.0e20,1.0e21,1.0e22,1.0e23,1.0e24,1.0e25,1.0e26,1.0e27,1.0e28,1…
	23 1.0e30,1.0e31,1.0e32,1.0e33,1.0e34,1.0e35,1.0e36,1.0e37,1.0e38,1…
	24 1.0e40,1.0e41,1.0e42,1.0e43,1.0e44,1.0e45,1.0e46,1.0e47,1.0e48,1…
	25 1.0e50,1.0e51,1.0e52,1.0e53,1.0e54,1.0e55,1.0e56,1.0e57,1.0e58,1…
	26 1.0e60,1.0e61,1.0e62,1.0e63,1.0e64,1.0e65,1.0e66,1.0e67,1.0e68,1…
	27 };
	28
	29 double
	30 __fmtpow10(int n)
	31 {
	32 int m;
	33
	34 if(n < 0) {
	35 n = -n;
	36 if(n < (int)(sizeof(tab)/sizeof(tab[0])))
	37 return 1/tab[n];
	38 m = n/2;
	39 return __fmtpow10(-m) * __fmtpow10(m-n);
	40 }
	41 if(n < (int)(sizeof(tab)/sizeof(tab[0])))
	42 return tab[n];
	43 m = n/2;
	44 return __fmtpow10(m) * __fmtpow10(n-m);
	45 }