who can explain? (reference)

[Mher Didaryan]

#include <iostream>

void func1(int &a);
void func2(const int &a);

int main()
{
double d = 5.5;
//func1(d); error,,, why?
func2(d); // no error,,, why?
return 0;
}

void func1(int &a)
{
std::cout << a << std::endl;
}

void func2(const int &a)
{
std::cout << a << std::endl;
}

[cire]

//func1(d); error,,, why?

d is not an int. The compiler can't create a temporary int to feed to the function because a non-const reference will not bind to a temporary.

func2(d); // no error,,, why?

In this case the compiler can create a temporary int to feed to the function because a const reference will bind to a temporary.

[Mher Didaryan]

thank you cire,,, but why a non-const reference will not bind to a temporary and a const reference will bind to a temporary?

[o1vk4iN6]

Modifying a temporary value doesn't make sense, it's to help prevent errors that can be caused by accidentally modifying a value that otherwise has no meaning being modified.

void func1(int &a)
{
    a = 10;
}

int main()
{
    double foo = 0;

    func1(foo); // if this was legal

    std::cout << foo; // outputs 0

}

[Mher Didaryan]

thanks a lot xerzi