ref: 68cda8f4a0a560c08ad8e025e334bd66f9ef2bcd
dir: /sys/src/cmd/python/Python/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;
}