How to Fix Comparison Error Between Pointer and Integer in C

Comparison Error in C : Pointer vs. Integer

When attempting to compile a simple function from Bjarne Stroustrup's C book, third edition, developers may encounter the compile time error:

error: ISO C++ forbids comparison between pointer and integer

This issue arises when comparing a pointer with an integer. In the provided code:

<code class="cpp">#include <iostream>
#include <string>
using namespace std;
bool accept()
{
    cout << "Do you want to proceed (y or n)?\n";
    char answer;
    cin >> answer;
    if (answer == "y") return true;
    return false;
}</code>

The error appears in the if statement where answer is compared to a string literal ("y"). Since answer is a character variable, it must be compared to a character constant.

Solution

There are two solutions to this issue:

1. Use a string Variable:
   Declare answer as a string type instead of char. This will allow you to compare answer to a string literal correctly:

   <code class="cpp">string answer;
   if (answer == "y") return true;</code>

2. Use Character Constant:
   Instead of comparing answer to a string literal, use a character constant enclosed in single quotes:

   <code class="cpp">if (answer == 'y') return true; // Note single quotes for character constant</code>

Both methods effectively resolve the error by ensuring that the comparison is between compatible types.

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