60 lines
1.1 KiB
C
60 lines
1.1 KiB
C
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#include <stdio.h>
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#include <ctype.h>
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#include <math.h>
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#define DEC_SEP X('.') X(',')
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#define EXP_SEP X('e') X('E')
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double atof(char *s);
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int main(int argc, char *argv[])
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{
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if (argc < 2) {
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printf("error: expected argument\n");
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return 1;
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}
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printf("%f\n", atof(argv[1]));
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return 0;
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}
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/* macros for atof */
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#define SIGN(s) \
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((*s == '-') ? (s++, -1) : ((*s == '+') ? (s++, 1) : 1))
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#define ATOI(s, x, ...) \
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for (; isdigit(*s); s++, ##__VA_ARGS__) \
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x = 10 * x + (*s - '0')
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/* atof: convert string s to double */
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double atof(char s[])
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{
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double val;
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while (isspace(*s))
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s++;
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/* integer part */
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int sign = SIGN(s);
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ATOI(s, val);
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#define X(sep) *s != sep &&
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if (DEC_SEP 1) return sign * val;
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#undef X
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s++;
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/* fractional part */
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int exp = 0;
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ATOI(s, val, exp--);
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val *= sign * pow(10, exp);
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#define X(sep) *s != sep &&
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if (EXP_SEP 1) return val;
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#undef X
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s++;
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/* exponent */
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sign = SIGN(s);
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exp = 0;
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ATOI(s, exp);
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return val * pow(10, sign * exp);
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}
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