Implicit casts between booleans and numbers in C++

Certainly! In C++, numeric types like int and float can be implicitly converted to the bool type. When this happens:

• The numeric value 0 (or 0.0, 0.0f, etc.) becomes false
• Any non-zero numeric value becomes true

Here's an example:

1#include <iostream>
2
3int main() {
4  bool value1 = 0;
5  bool value2 = 1;
6  bool value3 = -5;
7  bool value4 = 0.0;
8  bool value5 = 0.1f;
9
10   // Prints bools as true/false instead of 1/0
11  std::cout << std::boolalpha;
12
13  std::cout << value1 << '\n';  // Outputs false
14  std::cout << value2 << '\n';  // Outputs true
15  std::cout << value3 << '\n';  // Outputs true
16  std::cout << value4 << '\n';  // Outputs false
17  std::cout << value5 << '\n';  // Outputs true
18}

1false
2true
3true
4false
5true

As you can see, the integer values 1 and -5 both evaluate to true, because they are non-zero. The integer 0 and the floating point 0.0 both evaluate to false.

The opposite is also possible (though less common). true implicitly converts to the integer value 1, and false converts to 0.

This implicit conversion allows us to use the result of boolean expressions in arithmetic operations. But it's generally clearer to avoid this and keep arithmetic and boolean logic separate.