ref: c7fd8fe47a96d447d8ea327f14314fc1f55f377f
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;
}