c++ - 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_VALUE = std::numeric_limits<int>::max();
    ...
}

This declaration fails to compile with the following message:

numeric.cpp:8: error: 'std::numeric_limits::max()' cannot appear in a constant-expression numeric.cpp:8: error: a function call cannot appear in a constant-expression

I understand why this doesn't work, but two things look weird to me:

1. It seems to me a natural decision to use the value in constant expressions. Why did the language designers decide to make max() a function thus not allowing this usage?

2. The spec claims in 18.2.1 that

   For all members declared static const in the numeric_limits template, specializations shall define these values in such a way that they are usable as integral constant expressions.

   Doesn't it mean that I should be able to use it in my scenario and doesn't it contradict the error message?

Thank you.

Answer 1

Looks like a bit of a defect...

In C++0x, numeric_limits will have everything marked with constexpr, meaning you will be able to use min() and max() as compile-time constants.