Explicit type conversion

#include <cassert>
#include <iostream>
 
double f = 3.14;
unsigned int n1 = (unsigned int)f; // C-style cast
unsigned int n2 = unsigned(f);     // function-style cast
 
class C1;
class C2;
C2* foo(C1* p)
{
    return (C2*)p; // casts incomplete type to incomplete type
}
 
void cpp23_decay_copy_demo()
{
    auto inc_print = [](int& x, const int& y)
    {
        ++x;
        std::cout << "x:" << x << ", y:" << y << '\n';
    };
 
    int p{1};
    inc_print(p, p); // prints x:2 y:2, because param y here is an alias of p
    int q{1};
    inc_print(q, auto{q}); // prints x:2 y:1, auto{q} (C++23) casts to prvalue,
                           // so the param y is a copy of q (not an alias of q)
}
 
// In this example, C-style cast is interpreted as static_cast
// even though it would work as reinterpret_cast
struct A {};
struct I1 : A {};
struct I2 : A {};
struct D : I1, I2 {};
 
int main()
{
    D* d = nullptr;
//  A* a = (A*)d;                   // compile-time error
    A* a = reinterpret_cast<A*>(d); // this compiles
    assert(a == nullptr);
 
    cpp23_decay_copy_demo();
}