ref: a0e7c259c12866fcc551cb9da0bafdc8fd77a0db
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;
}