Thread: Atof with scientific notation

Ok, I coded a simple representation of an extended Atof:

Code:

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <math.h>

#ifndef MAXSIZE
  #define MAXSIZE 1000
#endif  
 
enum bool {TRUE = 1, FALSE = 0}; 

long double Atof(char* s)
{
   enum bool isNegative = FALSE;
   long double val, power; 
   int i, sign, exp;
   
   /* while it's a space, keep iterating */
   for(i = 0; isspace(s[i]); i++) 
   ; 
   /* record the sign */
   sign = (s[i] == '-')? -1 : 1;
   
   /* if it is a sign, just ignore it iterating to the next index */
   if(s[i] == '-' || s[i] == '+') 
     i++; 
   
   /* get the power and the value for further manipulation */
   
   /* ----------------------------------------------------- */
   
   for(val = 0.0; isdigit(s[i]); i++) 
     val = 10 * val + (s[i] - '0');            
   if(s[i] == '.') 
     i++; 
   for(power = 1.0; isdigit(s[i]); i++) 
   {  
     val = 10 * val + (s[i] - '0');
     power *= 10;   
   }
   
   /* ----------------------------------------------------- */ 
   
   /* just ignore if 'e' or 'E' was entered */
   
   if(s[i] == 'e' || s[i] == 'E') 
   { 
     i++;
     /* test if the exponent is negative */
     if(s[i] == '-') 
        isNegative = TRUE;
     i++;
     /* test if the next char is a digit */
     if(isdigit(s[i]))
        exp = s[i] - '0';         
           
     /* if the exponent is negative, make the exp value negative
      * and return the proper value */
     if(isNegative) 
     { 
       exp = -exp;
       return (sign * val / power) * pow(10.0, exp);  
     }
     /* the exponent isn't negative, so don't make the exp value negative */
     else { 
       return (sign * val / power) * pow(10.0, exp);  
     }
   }
   /* 'e' or 'E' wasn't entered, just return the value with the adequate sign */
   else { 
     return val * sign / power;  
   }                              
}

int main(void)
{
  char strnum[MAXSIZE];
  long double d;
  
  printf("Please enter a number in scientific notation of the form ");
  printf("[number]e-[exponent] or [number]E-[exponent]: ");      
  fgets(strnum, sizeof(strnum), stdin);
  
  d = Atof(strnum);
  printf("The double value in scientific notation is %Lf\n", d);
   
  return 0;   
}

I don't understand why even declaring my vars as long double, I can't get the precision offered by this type.