[boost] [static_if] Is there interest in a `static if` emulation library?

1 Sep 2014

      Hello all,

With C++14 generic lambdas, it is possible to implement a sort of
`static if` (see also N3613):

template< typename T >
void assign ( T& x, T const& y ) {
    x = y;

    static_if<boost::has_equal_to<T>::value>(
        std::bind([] ( auto x, auto y ) {
            assert(x == y);
            std::cout << "asserted for: " << typeid(T).name() << std::endl;
        }, x, y)
    ).else_(
        [] ( ) {
            std::cout << "cannot assert for: " << typeid(T).name() << std::endl;
        }
    );
}

The bind around the generic lambda is a bit verbose... but this code
compiles, asserts when called on int, and does not assert when called
on x_t (tested on clang 3.4.2):

    int i = 1;
    struct x_t { } x;

    assign(i, i); // asserts
    assign(x, x); // does not assert

I have attached a reference implementation.

Thank you.
--Lorenzo

P.S. I didn't do much background research... sorry if this topic has
already been considered and discussed in Boost.

[boost] [static_if] Is there interest in a `static if` emulation library?

Lorenzo Caminiti