Why can't nullptr convert to int?

Question

Summary: nullptr converts to bool, and bool converts to int, so why doesn't nullptr convert to int?

This code is okay:

void f(bool);
f(nullptr);      // fine, nullptr converts to bool

And this is okay:

bool b;
int i(b);        // fine, bool converts to int

So why isn't this okay?

void f(int);
f(nullptr);      // why not convert nullptr to bool, then bool to int?

Answer 1

Because it is exactly the main idea of nullptr.

nullptr was meant to avoid this behavior:

struct myclass {};

void f(myclass* a) { std::cout << "myclass\n"; }
void f(int a) { std::cout << "int\n"; }

// ...

f(NULL); // calls void f(int)

If nullptr were convertible to int this behavior would occur.

So the question is "why is it convertible to bool?".

Syntax-"suggarness":

int* a = nullptr;
if (a) {
}

Which looks way better than:

if (a == nullptr) {
}