Thread: is_pointer<T> trait question.

I came upon this sample code which the author said that std::is_pointer<T>::value always evaluate to false. The author didn't explain why this doesn't work and I haven't been able to find an explainable after search the web.This code wouldn't compile either with the error "incompatible operand type 'int' and 'int*'; i think this maybe related to the 'false' evaluation of the std::is_pointer<T>::value.

So what makes std::is_pointer<T>::value always evaluated to false in this case?

Code:

template <typename T>
void foo_bad(const T& val) {
   std::cout << (std::is_pointer<T>::value ? *val : val)                     
                  << std::endl;
}

The compilation error has nothing to do with is_pointer.

The "test ? a : b" expression requires a and b to be of the same (or compatible) types. *val and val are not.

I came upon this sample code which the author said that std::is_pointer<T>::value always evaluate to false.

O_o

Assuming you didn't copy the wrong code, the author is simply wrong.

[Edit]
The code is broken as grumpy explains.

I'm saying that `std::is_pointer<T>::value' would not always be false when the code is otherwise corrected.
[/Edit]

Soma