boost/hana/bool.hpp
/*! @file Defines the `Logical` and `Comparable` models of `boost::hana::integral_constant`. @copyright Louis Dionne 2013-2017 Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) */ #ifndef BOOST_HANA_BOOL_HPP #define BOOST_HANA_BOOL_HPP #include <boost/hana/fwd/bool.hpp> #include <boost/hana/concept/integral_constant.hpp> #include <boost/hana/config.hpp> #include <boost/hana/core/to.hpp> #include <boost/hana/core/when.hpp> #include <boost/hana/detail/operators/arithmetic.hpp> #include <boost/hana/detail/operators/comparable.hpp> #include <boost/hana/detail/operators/logical.hpp> #include <boost/hana/detail/operators/orderable.hpp> #include <boost/hana/eval.hpp> #include <boost/hana/fwd/core/tag_of.hpp> #include <boost/hana/fwd/eval_if.hpp> #include <boost/hana/fwd/if.hpp> #include <boost/hana/fwd/value.hpp> #include <cstddef> #include <type_traits> #include <utility> BOOST_HANA_NAMESPACE_BEGIN ////////////////////////////////////////////////////////////////////////// // integral_constant ////////////////////////////////////////////////////////////////////////// //! @cond namespace ic_detail { template <typename T, T N, typename = std::make_integer_sequence<T, N>> struct go; template <typename T, T N, T ...i> struct go<T, N, std::integer_sequence<T, i...>> { using swallow = T[]; template <typename F> static constexpr void with_index(F&& f) { (void)swallow{T{}, ((void)f(integral_constant<T, i>{}), i)...}; } template <typename F> static constexpr void without_index(F&& f) { (void)swallow{T{}, ((void)f(), i)...}; } }; template <typename T, T v> template <typename F> constexpr void with_index_t<T, v>::operator()(F&& f) const { go<T, ((void)sizeof(&f), v)>::with_index(static_cast<F&&>(f)); } template <typename T, T v> template <typename F> constexpr void times_t<T, v>::operator()(F&& f) const { go<T, ((void)sizeof(&f), v)>::without_index(static_cast<F&&>(f)); } // avoid link-time error template <typename T, T v> constexpr with_index_t<T, v> times_t<T, v>::with_index; } // avoid link-time error template <typename T, T v> constexpr ic_detail::times_t<T, v> integral_constant<T, v>::times; template <typename T, T v> struct tag_of<integral_constant<T, v>> { using type = integral_constant_tag<T>; }; //! @endcond ////////////////////////////////////////////////////////////////////////// // Operators ////////////////////////////////////////////////////////////////////////// namespace detail { template <typename T> struct comparable_operators<integral_constant_tag<T>> { static constexpr bool value = true; }; template <typename T> struct orderable_operators<integral_constant_tag<T>> { static constexpr bool value = true; }; template <typename T> struct arithmetic_operators<integral_constant_tag<T>> { static constexpr bool value = true; }; template <typename T> struct logical_operators<integral_constant_tag<T>> { static constexpr bool value = true; }; } #define BOOST_HANA_INTEGRAL_CONSTANT_BINARY_OP(op) \ template <typename U, U u, typename V, V v> \ constexpr integral_constant<decltype(u op v), (u op v)> \ operator op(integral_constant<U, u>, integral_constant<V, v>) \ { return {}; } \ /**/ #define BOOST_HANA_INTEGRAL_CONSTANT_UNARY_OP(op) \ template <typename U, U u> \ constexpr integral_constant<decltype(op u), (op u)> \ operator op(integral_constant<U, u>) \ { return {}; } \ /**/ // Arithmetic BOOST_HANA_INTEGRAL_CONSTANT_UNARY_OP(+) // Bitwise BOOST_HANA_INTEGRAL_CONSTANT_UNARY_OP(~) BOOST_HANA_INTEGRAL_CONSTANT_BINARY_OP(&) BOOST_HANA_INTEGRAL_CONSTANT_BINARY_OP(|) BOOST_HANA_INTEGRAL_CONSTANT_BINARY_OP(^) BOOST_HANA_INTEGRAL_CONSTANT_BINARY_OP(<<) BOOST_HANA_INTEGRAL_CONSTANT_BINARY_OP(>>) #undef BOOST_HANA_INTEGRAL_CONSTANT_UNARY_OP #undef BOOST_HANA_INTEGRAL_CONSTANT_BINARY_OP ////////////////////////////////////////////////////////////////////////// // User-defined literal ////////////////////////////////////////////////////////////////////////// namespace ic_detail { constexpr int to_int(char c) { int result = 0; if (c >= 'A' && c <= 'F') { result = static_cast<int>(c) - static_cast<int>('A') + 10; } else if (c >= 'a' && c <= 'f') { result = static_cast<int>(c) - static_cast<int>('a') + 10; } else { result = static_cast<int>(c) - static_cast<int>('0'); } return result; } template<std::size_t N> constexpr long long parse(const char (&arr)[N]) { long long base = 10; std::size_t offset = 0; if (N > 2) { bool starts_with_zero = arr[0] == '0'; bool is_hex = starts_with_zero && arr[1] == 'x'; bool is_binary = starts_with_zero && arr[1] == 'b'; if (is_hex) { //0xDEADBEEF (hexadecimal) base = 16; offset = 2; } else if (is_binary) { //0b101011101 (binary) base = 2; offset = 2; } else if (starts_with_zero) { //012345 (octal) base = 8; offset = 1; } } long long number = 0; long long multiplier = 1; for (std::size_t i = 0; i < N - offset; ++i) { char c = arr[N - 1 - i]; if (c != '\'') { // skip digit separators number += to_int(c) * multiplier; multiplier *= base; } } return number; } } namespace literals { template <char ...c> constexpr auto operator"" _c() { return hana::llong<ic_detail::parse<sizeof...(c)>({c...})>{}; } } ////////////////////////////////////////////////////////////////////////// // Model of Constant/IntegralConstant ////////////////////////////////////////////////////////////////////////// template <typename T> struct IntegralConstant<integral_constant_tag<T>> { static constexpr bool value = true; }; template <typename T, typename C> struct to_impl<integral_constant_tag<T>, C, when<hana::IntegralConstant<C>::value>> : embedding<is_embedded<typename C::value_type, T>::value> { template <typename N> static constexpr auto apply(N const&) { return integral_constant<T, N::value>{}; } }; ////////////////////////////////////////////////////////////////////////// // Optimizations ////////////////////////////////////////////////////////////////////////// template <typename T> struct eval_if_impl<integral_constant_tag<T>> { template <typename Cond, typename Then, typename Else> static constexpr decltype(auto) apply(Cond const&, Then&& t, Else&& e) { constexpr bool cond = static_cast<bool>(Cond::value); return eval_if_impl::apply(hana::bool_<cond>{}, static_cast<Then&&>(t), static_cast<Else&&>(e)); } template <typename Then, typename Else> static constexpr decltype(auto) apply(hana::true_ const&, Then&& t, Else&&) { return hana::eval(static_cast<Then&&>(t)); } template <typename Then, typename Else> static constexpr decltype(auto) apply(hana::false_ const&, Then&&, Else&& e) { return hana::eval(static_cast<Else&&>(e)); } }; template <typename T> struct if_impl<integral_constant_tag<T>> { template <typename Cond, typename Then, typename Else> static constexpr decltype(auto) apply(Cond const&, Then&& t, Else&& e) { constexpr bool cond = static_cast<bool>(Cond::value); return if_impl::apply(hana::bool_<cond>{}, static_cast<Then&&>(t), static_cast<Else&&>(e)); } //! @todo We could return `Then` instead of `auto` to sometimes save //! a copy, but that would break some code that would return a //! reference to a `type` object. I think the code that would be //! broken should be changed, but more thought needs to be given. template <typename Then, typename Else> static constexpr auto apply(hana::true_ const&, Then&& t, Else&&) { return static_cast<Then&&>(t); } template <typename Then, typename Else> static constexpr auto apply(hana::false_ const&, Then&&, Else&& e) { return static_cast<Else&&>(e); } }; BOOST_HANA_NAMESPACE_END #endif // !BOOST_HANA_BOOL_HPP