On Wednesday, 23 December 2020 at 20:56:26 UTC, jmh530 wrote:
doing similar things). Abusing C++'s syntax you might have
something like
concept Bar(T) = requires(U)() {
Foo!U; //akin to something like typename T::Foo<U>;
}
where we would basically be telling the compiler that T has to
be a Foo!U, which would mean you would have to use Bar like
Bar!U...at least that's the idea. I don't think anything like
this would work currently in C++.
I don't use concepts yet as it is a very new C++ feature. The
following code does not work in XCode, although it probably
should according to cppreference. So take this with a grain of
salt (other variations should be possible):
namespace detail {
template<template<typename> typename F, class U>
constexpr void _is_instantiable(F<U> a){}
}
template<class T>
struct Foo{};
template<class T>
concept Fooish = requires(T a){
detail::_is_instantiable<Foo>(a);
};