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v0.5.1
https://github.com/python/cpython
09 December 2020, 11:06:31 UTC
Revision 1fae982b9b6fff5a987a69856b91339e5d023838 authored by Benjamin Peterson on 25 June 2016, 21:03:21 UTC, committed by Benjamin Peterson on 25 June 2016, 21:03:21 UTC 
2.7.12 final
1 parent 95d9555
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Tip revision: 1fae982b9b6fff5a987a69856b91339e5d023838 authored by Benjamin Peterson on 25 June 2016, 21:03:21 UTC
2.7.12 final
Tip revision: 1fae982
atof.c 

/* Just in case you haven't got an atof() around...
   This one doesn't check for bad syntax or overflow,
   and is slow and inaccurate.
   But it's good enough for the occasional string literal... */

#include "pyconfig.h"

#include <ctype.h>

double atof(char *s)
{
    double a = 0.0;
    int e = 0;
    int c;
    while ((c = *s++) != '\0' && isdigit(c)) {
        a = a*10.0 + (c - '0');
    }
    if (c == '.') {
        while ((c = *s++) != '\0' && isdigit(c)) {
            a = a*10.0 + (c - '0');
            e = e-1;
        }
    }
    if (c == 'e' || c == 'E') {
        int sign = 1;
        int i = 0;
        c = *s++;
        if (c == '+')
            c = *s++;
        else if (c == '-') {
            c = *s++;
            sign = -1;
        }
        while (isdigit(c)) {
            i = i*10 + (c - '0');
            c = *s++;
        }
        e += i*sign;
    }
    while (e > 0) {
        a *= 10.0;
        e--;
    }
    while (e < 0) {
        a *= 0.1;
        e++;
    }
    return a;
}
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