How can i check if given int(or any other data type) is signed or unsigned? I found this function while searching,
std::numeric_limits<int>::is_signed
But i can only input the data type, is there a way that i can check by variable name, like.
signed int x = 5;
Now i want to make a function which checks that x is a signed int or not.
And if you guys can answer these little questions, that would be highly appreciated.
is there a way that i can check by variable name
Since C++11, we have decltype to get the type of a variable or expression:
std::numeric_limits<decltype(x)>::is_signed
Historically, it was trickier; the only way to infer a type from a variable was through template argument deduction:
template <typename T>
bool is_signed(T const &) {
return std::numeric_limits<T>::is_signed;
}
Why do we use '::' these operators after std?
That's the scope resolution operator, saying that we want the name numeric_limits to be looked up in the namespace std.
What do they mean when we use them in
std::cout, is it the same?
Yes. Like most names in the standard library, cout is also scoped inside namespace std.
Here
numeric_limits<>is a class or what?
It's a class template, containing various static variables and functions that describe the type used as the template argument. Here's a reference: http://en.cppreference.com/w/cpp/types/numeric_limits
And again, why are we using these '::' before is_signed?
Again, that resolves the scope by saying we want the name is_signed to be looked up inside the class scope of std::numeric_limits<int>.