When are temporary variables created by C++ compiler?

[chinmay.sahoo]

Provided that function parameter is a "const reference", compiler generates temporary variable in following2 ways.

a) The actual argument is the correct type, but it isn't Lvalue

double Cube(const double & num)
{
num = num * num * num;
return num;
}
double temp = 2.0;
double value = cube(3.0 + temp); // argument is a expression and not a Lvalue;

b) The actual argument is of the wrong type, but of a type that can be converted to the correct type

long temp = 3L;
double value = cuberoot ( temp); // long to double conversion