Python/atof.c

   1
   2 /* Just in case you haven't got an atof() around...
   3    This one doesn't check for bad syntax or overflow,
   4    and is slow and inaccurate.
   5    But it's good enough for the occasional string literal... */
   6
   7 #include "pyconfig.h"
   8
   9 #include <ctype.h>
  10
  11 double atof(char *s)
  12 {
  13         double a = 0.0;
  14         int e = 0;
  15         int c;
  16         while ((c = *s++) != '\0' && isdigit(c)) {
  17                 a = a*10.0 + (c - '0');
  18         }
  19         if (c == '.') {
  20                 while ((c = *s++) != '\0' && isdigit(c)) {
  21                         a = a*10.0 + (c - '0');
  22                         e = e-1;
  23                 }
  24         }
  25         if (c == 'e' || c == 'E') {
  26                 int sign = 1;
  27                 int i = 0;
  28                 c = *s++;
  29                 if (c == '+')
  30                         c = *s++;
  31                 else if (c == '-') {
  32                         c = *s++;
  33                         sign = -1;
  34                 }
  35                 while (isdigit(c)) {
  36                         i = i*10 + (c - '0');
  37                         c = *s++;
  38                 }
  39                 e += i*sign;
  40         }
  41         while (e > 0) {
  42                 a *= 10.0;
  43                 e--;
  44         }
  45         while (e < 0) {
  46                 a *= 0.1;
  47                 e++;
  48         }
  49         return a;
  50 }