forked from mpusz/mp-units
134 lines
4.3 KiB
C++
134 lines
4.3 KiB
C++
// The MIT License (MIT)
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//
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// Copyright (c) 2018 Mateusz Pusz
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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#pragma once
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#include <units/bits/basic_concepts.h>
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#include <units/bits/dimension_op.h>
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namespace units {
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template<Dimension D, UnitOf<D> U, Representation Rep>
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class quantity;
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template<Dimension D, UnitOf<D> U>
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struct reference;
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namespace detail {
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template<typename D, typename D1, typename U1, typename D2, typename U2>
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using reference_multiply_impl = reference<D, downcast_unit<D,
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(U1::ratio / dimension_unit<D1>::ratio) * (U2::ratio / dimension_unit<D2>::ratio) * dimension_unit<D>::ratio>>;
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template<typename D, typename D1, typename U1, typename D2, typename U2>
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using reference_divide_impl = reference<D, downcast_unit<D,
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(U1::ratio / dimension_unit<D1>::ratio) / (U2::ratio / dimension_unit<D2>::ratio) * dimension_unit<D>::ratio>>;
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} // namespace detail
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template<Reference R1, Reference R2>
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using reference_multiply = detail::reference_multiply_impl<
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dimension_multiply<typename R1::dimension, typename R2::dimension>,
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typename R1::dimension, typename R1::unit, typename R2::dimension, typename R2::unit>;
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template<Reference R1, Reference R2>
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using reference_divide = detail::reference_divide_impl<
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dimension_divide<typename R1::dimension, typename R2::dimension>,
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typename R1::dimension, typename R1::unit, typename R2::dimension, typename R2::unit>;
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/**
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* @brief The type for quantity references
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*
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* This type is intended to be used in the quantity references definition:
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*
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* @code{.cpp}
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* namespace length_references {
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*
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* inline constexpr auto m = reference<dim_length, metre>{};
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* inline constexpr auto km = reference<dim_length, kilometre>{};
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*
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* }
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*
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* namespace references {
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*
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* using namespace length_references;
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*
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* }
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* @endcode
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*
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* Quantity references simplify quantity creation:
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*
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* @code{.cpp}
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* using namespace units::isq::si::references;
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*
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* auto d = 123 * m;
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* auto v = 70 * (km / h);
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* @endcode
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*
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* Also, it is allowed to define custom quantity references from existing ones:
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*
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* @code{.cpp}
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* constexpr auto Nm = N * m;
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* constexpr auto mph = mi / h;
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* @endcode
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*
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* The following syntaxes are not allowed:
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* `2 / s`, `km * 3`, `s / 4`, `70 * km / h`.
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*/
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template<Dimension D, UnitOf<D> U>
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struct reference {
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using dimension = D;
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using unit = U;
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// Hidden Friends
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// Below friend functions are to be found via argument-dependent lookup only
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template<Reference R2>
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[[nodiscard]] friend constexpr reference_multiply<reference, R2> operator*(reference, R2) { return {}; }
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template<Reference R2>
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[[nodiscard]] friend constexpr reference_divide<reference, R2> operator/(reference, R2) { return {}; }
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template<Representation Rep>
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[[nodiscard]] friend constexpr Quantity auto operator*(const Rep& lhs, reference)
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{
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return quantity<D, U, Rep>(lhs);
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}
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friend void /*Use `q * (1 * r)` rather than `q * r`.*/ operator*(Quantity auto, reference) = delete;
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template<Reference R2>
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[[nodiscard]] friend constexpr bool operator==(reference, R2) { return false; }
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[[nodiscard]] friend constexpr bool operator==(reference, reference) { return true; }
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};
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// type traits
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namespace detail {
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template<typename D, typename U>
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inline constexpr bool is_reference<reference<D, U>> = true;
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} // namespace detail
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} // namespace units
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