The Exotic Library API Idiom: a simple structure for separating internals from the public interface. Yeah, I really love naming things!

exotic_lib_api_idiom.hpp

// Copyright (c) October 2026 Félix-Olivier Dumas. All rights reserved.
// Licensed under the terms described in the LICENSE file

namespace exotic::internal::foo {

    namespace detail {

        template<typename T>
        struct impl {
            using value_type = T;

            void run();
        };

    }

    namespace api {

        // generic API
        template<typename T>
        struct custom : detail::impl<T> {};

        // specialized APIs can be added here
        struct standard : custom<int> {};

    }

}


// public facade
namespace exotic {

    template<typename T>
    using foo = internal::foo::api::custom<T>;

    using standard_foo = internal::foo::api::standard;

}


// user code only sees the facade :)
exotic::foo<float> a;
exotic::standard_foo b;