#ifndef METAL_LAMBDA_ALWAYS_HPP
#define METAL_LAMBDA_ALWAYS_HPP

#include "../config.hpp"

namespace metal {
/// \cond
namespace detail {
    template <class val>
    struct _always;
}
/// \endcond

/// \ingroup lambda
///
/// ### Description
/// Lifts a \value to an n-ary \lambda that always evaluates to that \value,
/// regardless of the argument(s) it's [invoked](\ref invoke) with.
///
/// ### Usage
/// For any and \value `val`
/// \code
///     using result = metal::always<val>;
/// \endcode
///
/// \returns: \lambda
/// \semantics:
///     Equivalent to
///     \code
///         using result = metal::lambda<expr>;
///     \endcode
///     where `expr` is an \expression such that
///     \code
///         template<class...>
///         using expr = val;
///     \endcode
///
/// ### Example
/// \snippet lambda.cpp always
///
/// ### See Also
/// \see lambda, invoke, partial, bind
template <class val>
using always = typename detail::_always<val>::type;
}

#include "../lambda/lambda.hpp"
#include "../value/identity.hpp"

namespace metal {
/// \cond
namespace detail {
    template <class val>
    struct _always {
        template <class...>
        using impl = identity<val>;

        using type = lambda<impl>;
    };
}
/// \endcond
}

#endif