Thread: Few questions from "Accelerated C++"

Hi all,

I'm going through Accelerated C++ (great book by the way!) and I've written a simple program (similar to the padding program on Chapter 2) but there's a warning from gcc (with the options -Wall -pedantic) and cannot figure out how to solve it.

The problem is that there is a comparison between signed and unsugned integers in the line:

Code:

if (r==pad+1 && c==pad+1) {

I've tried defining pad as

Code:

string::size_type pad=0;

instead of int, but that doesn't work. Can someone please explain why I get this warning message and how to avoid it?

Here's my program:

Code:

#include<iostream>
#include<string>

using std::cin;
using std::cout;
using std::endl;
using std::string;

int main()
{
        cout << "Please enter your name: ";
        string name;
        cin >> name;
        const string greeting = "Hello " + name + "!";

        cout << "Please enter how much padding you'd like: ";
        int pad=0;
        cin >> pad;

        const int rows=2*pad+3;
        const string::size_type cols=greeting.size()+2*pad+2;

        for (int r=0; r!=rows; ++r) {
                string::size_type c=0;
                while (c!=cols) {
                        if (r==pad+1 && c==pad+1) {
                                cout << greeting;
                                c+=greeting.size();
                        }
                        else if (r==0 || r==rows-1 || c==0 || c==cols-1) {
                                cout << "*";
                                ++c;
                        }
                        else {
                                cout << " ";
                                ++c;
                        }
                }
                cout << endl;
        }
        return 0;
}

Thanks

Spiros

ps I'm sure I'll have plenty more questions in the near future so I'll keep posting them on this thread instead of creating new threads etc..

Even if you declare 'pad' as 'string::size_type' 'r' would still be an 'int'.

Soma

Originally Posted by Daved

The book might just be ignoring the error.

I don't think it's an error. A good compiler will warn, though.

cheers, that helped a lot. I thought that long int's where unsigned, but it seems I read the manual wrong. I changed the variables in question to unsigned int's and there's no problem at all now.

Thanks!