Thread: Implement atof

Write code to implement atof (string to float)

Code:

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;
}

#include<iostream>

using namespace std;

double atof( char *s)
{
int sign=1

if(s == NULL)
return 0;
if( *s == '-')
sign=-1;
double out=0;
while( s !=NULL || *s !='\0')
{
if(*s == ' ')
continue;
if(*s == '.')
break;
if( *s > '9' || *s < '0')
return 0;
out= out*10+(*s - '0');
s++;
}
double decimalOut=0;
int decCount=0;
while( s != NULL && *s == '.')
{
if(*s == ' ')
continue;
if(*s == '\0')
break;
if( *s > '9' || *s < '0')
return 0;
decimal= decimal*10+(*s - '0');
decimalCount++;
}

return sign*(out + (0.1 ^ decimalCount)*decimalcount);
}