73 lines
1.9 KiB
C
73 lines
1.9 KiB
C
#include "Rts.h"
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#include <stdint.h>
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#define BYTEBUILD_DOUBLE_PRECISION 0.00000000000001
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HsInt bytebuild_paste_double(char *s0, HsInt off, double n) {
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char* s = s0 + off;
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// handle special cases
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if (n == 0 || isnan(n) || isinf(n)) {
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*s = '0';
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return 1;
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} else {
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int digit, m, m1;
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char *c = s;
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int neg = (n < 0);
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if (neg)
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n = -n;
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// calculate magnitude
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m = log10(n);
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int useExp = (m >= 14 || (neg && m >= 9) || m <= -9);
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if (neg)
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*(c++) = '-';
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// set up for scientific notation
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if (useExp) {
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if (m < 0)
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m -= 1.0;
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n = n / pow(10.0, m);
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m1 = m;
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m = 0;
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}
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if (m < 1.0) {
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m = 0;
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}
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// convert the number
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while (n > BYTEBUILD_DOUBLE_PRECISION || m >= 0) {
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double weight = pow(10.0, m);
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if (weight > 0 && !isinf(weight)) {
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digit = floor(n / weight);
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n -= (digit * weight);
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*(c++) = '0' + digit;
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}
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if (m == 0 && n > 0)
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*(c++) = '.';
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m--;
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}
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if (useExp) {
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// convert the exponent
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int i, j;
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*(c++) = 'e';
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if (m1 > 0) {
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*(c++) = '+';
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} else {
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*(c++) = '-';
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m1 = -m1;
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}
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m = 0;
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while (m1 > 0) {
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*(c++) = '0' + m1 % 10;
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m1 /= 10;
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m++;
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}
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c -= m;
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for (i = 0, j = m-1; i<j; i++, j--) {
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// swap without temporary
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c[i] ^= c[j];
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c[j] ^= c[i];
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c[i] ^= c[j];
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}
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c += m;
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}
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return (c - s);
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}
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}
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