Using numeric_limits::max() in constant expressions

Question

I would like to define inside a class a constant which value is the maximum possible int. Something like this:

class A
{
    ...
    static const int ERROR_V         


        

Answer 1

While the current standard lacks support here, for integral types Boost.IntegerTraits gives you the compile time constants const_min and const_max.

The problem arises from §9.4.2/4:

If a static data member is of const integral or const enumeration type, its declaration in the class definition can specify a constant-initializer which shall be an integral constant expression (5.19). In that case, the member can appear in integral constant expressions.

Note that it adds:

The member shall still be defined in a name- space scope if it is used in the program and the namespace scope definition shall not contain an initializer.

As others already mentioned numeric_limits min() and max() simply aren't integral constant expressions, i.e. compile time constants.