Question

the operator int() function converts the string to an int

class mystring
{ 
  private:
    chat str[20];

  public:
   operator int()             // i'm assuming this converts a string to an int
   {
     int i=0,l,ss=0,k=1;

     l = strlen(str)-1;
     while(l>=0)
     {
       ss=ss+(str[l]-48)*k;
       l--;
       k*=10;
     }
     return(ss);
   } 
}

int main()
{
  mystring s2("123");
  int i=int(s2);
  cout << endl << "i= "<<i;
}

So what’s the logic behind operator int() ? What’s the 48 in there? Can someone explain to me the algorithm behind the conversion from string to int.

Answer 1

Yes this converts a string to an integer. 48 is the ASCII value for ‘0’. If you subtract 48 from an ASCII digit you’ll get the value of the digit (ex: ‘0’ – 48 = 0, ‘1’ – 48 = 1, ..). For each digit, your code calculates the correct power of 10 by using k (ranges between 1…10^{ log of the number represented by the input string}).