static_assert on initializer_list::size()

Question

Why is std::initializer_list<_E>::size not allowable in a static_assert, even though it\'s declared as a constexpr in my libstdc++ (v. 4.6)?

For example, the foll

Answer 1

Use following syntax:

LIVE DEMO

#include 

template
class Point
{
    std::initializer_list data;
public:
    constexpr Point(std::initializer_list init)
        : data
        (
            init.size() == Length ?
            init : throw 0
        )
    {}
};

int main()
{
    constexpr Point a{{1,2,3}};
    constexpr Point b{{1,2,3}}; // compile time error
}

Refer following SO.

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EDIT: Interesting that works on GCC 4.8.1, but does not work on Clang 3.4. Maybe this is related to constexpr of .size() (afaik, in C++14 it is constexpr).