build/_deps/metal-src/include/metal/map/map.hpp

#ifndef METAL_MAP_MAP_HPP
#define METAL_MAP_MAP_HPP

#include "../config.hpp"
#include "../lambda/apply.hpp"
#include "../lambda/lambda.hpp"
#include "../list/list.hpp"
#include "../list/transform.hpp"
#include "../number/if.hpp"
#include "../pair/pair.hpp"

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

/// \ingroup map
///
/// ### Description
/// Checks whether some \value is a \map.
///
/// ### Usage
/// For any \value `val`
/// \code
///     using result = metal::is_map<val>;
/// \endcode
///
/// \returns: \number
/// \semantics:
///     If `val` is a \map, then
///     \code
///         using result = metal::true_;
///     \endcode
///     otherwise
///     \code
///         using result = metal::false_;
///     \endcode
///
/// ### Example
/// \snippet map.cpp is_map
///
/// ### See Also
/// \see map, is_value, is_number, is_lambda, is_pair, is_list
template <class val>
using is_map = typename detail::_is_map<val>::type;

/// \ingroup map
///
/// ### Description
/// Constructs a \map out of a sequence of \pairs.
///
/// ### Usage
/// For any \pairs `pair_0, ..., pair_n-1`
/// \code
///     using result = metal::map<pair_0, ..., pair_n-1>;
/// \endcode
///
/// \pre: No two \pairs have the same key
/// \returns: \map
///
/// ### See Also
/// \see is_map
template <class... pairs>
using map = metal::if_<metal::is_map<metal::list<pairs...>>, metal::list<pairs...>>;

/// \ingroup map
///
/// ### Description
/// Constructs a \map out of any \value that is a specialization of a
/// template class or union whose template parameters are all themselves
/// specializations of template classes or unions that take exactly two
/// template parameters, the first \values of which are all distinct.
///
/// ### Usage
/// For any \value `val`
/// \code
///     using result = metal::as_map<val>;
/// \endcode
///
/// \returns: \map
///
/// ### Example
/// \snippet map.cpp as_map
///
/// ### See Also
/// \see map
template <class val>
using as_map = metal::apply<
    metal::lambda<metal::map>,
    metal::transform<metal::lambda<metal::as_pair>, metal::as_list<val>>>;
}

#include "../number/number.hpp"
#include "../value/distinct.hpp"

namespace metal {
/// \cond
namespace detail {
    template <class val>
    struct _is_map : false_ {
    };

    template <>
    struct _is_map<list<>> : true_ {
    };

    template <class... keys, class... vals>
    struct _is_map<list<list<keys, vals>...>> : distinct<keys...> {
    };
}
/// \endcond
}

#endif