Question

converting strings to floats without using stdlib.h or string.h

Answer 1

#include<stdio.h>
float stofloat(char *);

int main() {
char ch[20];// take maximum 19 length string
float i;
printf("\n enter the number as a string\n");
scanf("%[^\n]", ch);//*take a string with digit like float value
i = stofloat(ch); // in this function passing base address of the string
printf(" string =%s , float =%g \n", ch, i); // print orginal string and converted float value

return 0;
}

float stofloat(char *p) // p is a pointer which holds base address of ch string and return float value

{
// take two variables for counting the number of digits in mantissa
int i, num = 0, num2 = 0, pnt= 0, x = 0, y = 1;
float f1, f2, f3;
for (i = 0; p[i]; i++) //this loop will continue up to decimal point
if (p[i] == '.') {
pnt = i;
break;
}
for (i = 0; p[i]; i++) // this loop will cotnue up to end of the string

{
if (i < pnt)

num = num * 10 + (p[i] - 48);
else if (i == pnt)

continue;
else {
num2 = num2 * 10 + (p[i] - 48);
++x;
}
}
// it takes 10 if it has 1 digit ,100 if it has 2 digits in mantissa
for (i = 1; i <= x; i++)
y = y * 10;
f2 = num2 / (float) y;
f3 = num + f2;
return f3;
}

output1:

enter the number as a string                                                                                                 

005.549                                                                                                                       

string =005.549 , float =5.549  

output2:

enter the number as a string                                                                                                 

3.34                                                                                                                          

string =3.34 , float =3.34