ref: dce2c66c1a97657bd90dfa35cd76d7efc61d5f5b
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;
}