ref: 121ff4e951df1d5d2076d85292d5f5a3ad74765e
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;
}