Why int& a = is not allowed in C++?

Question

I am reading about references in C++. It says that int& a = 5 gives compile time error.

In Thinking in C++ - Bruce Eckel, author says that

Answer 1

int& a = 5;

In order for the above code to work, int& needs to bind to a temporary object of type int created out of the expression 5. But binding int& to a temporay didn't appeal to Bjarne Stroustrup — and he gave an example, similar to the following, to illustrate his point:

void f(int &i) { ++i; }

float x = 10.0;
f(x); 
std::cout << x <<< std::endl;

What will the std::cout print¹? Looks like it will print 11.

It feels, ++i is changing the argument x, but it doesn't. This is one reason why the creator of C++ didn't permit temporaries to bind to non-const reference.

However, you can do this:

int const & i = 10;
int const & j = x; //x is float

And since C++11, you can do this:

int && i = 10;
int && i = x; //x is float

Hope that helps.

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^{1. assuming int& can bind to the temporary created out of x.}