Question

I don’t know how to convert a string value to double or float. Here is the sample string I am trying to convert: "3.45667". I am struggling with the handling of the dot.

I tried this but it is not working:

#include<stdio.h>

int main()
{
    char string_array[] = { "3.45667" };
    float float_array[20], index = 0;

    for(index = 0 ; index < 7 ; index++)
    {
        if(string_array[index] == '.')
        {
            printf("dot");
            // here, how to add dot to the float_array?
        } else
        {
            float_array = (float)(string_array[index] - '0');
        }
    }
    return 0;
}

How to add a decimal point in the above code? I think this could be done with exponent form but I don’t know how to use exponent form.

Answer 1

The following program just counts how many digits are after the decimal point and scales the result in the end, instead of each digit.

float result = 0.0;
float scale  = 0.0;

char *s = "3.14567":

while (*s) {
     if (*s >= '0' && *s <= '9') {
        result = 10.0 * result + (float)(*s - '0');
        scale *= 10.0;
     }
     else if (*s == '.') scale = 1.0;
     else  { /* ERROR HANDLING */ }
     s++;
}
result = result / (scale == 0.0 ? 1.0 : scale)