Question

If I have the following code:

int a = 1;
bool b = 1;

Does a equal to b? Even the program might return that they are the same, are they actually equal in all aspects in low level?

Also, if I use code (pseudo) such as:

if (a)
then execute();

will execute() run? I am asking for theoretical answers, and I can’t convince myself with experiments as this is not natural science. Thank you all.

Answer 1

I think you can convince yourself with the right experiments:

#include <type_traits>

int main() {
    int a = 1;
    bool b = 1;
    static_assert(! std::is_same<decltype(a), decltype(b)>::value,
                  "No, they are not the same on all aspects");
}

Perhaps the most important difference between the two is that bool can only have two values: true and false, while int can have many more. Here’s another experiment that shows a consequence of this:

#include <cassert>

int main() {
    int a = 2;
    bool b = 2;
    assert(a != b);
}

The two types may seem similar because there are implicit conversions between the two. Any integral expression that is zero can be implicitly converted to false, and any integral expression that is not zero can be implicitly converted to true. In the opposite direction, false can be implicitly converted to zero, and true converted to one. This leads to the code above ending up testing if 2 != 1.

Now the answer to the question of whether execute(); is called in the snippet from the question should be obvious: the value a will be converted to a bool in the if statement, and since it is not zero, it will convert to true and result in a call to execute().