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mp-units/src/core/include/units/reference.h
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// The MIT License (MIT)
//
// Copyright (c) 2018 Mateusz Pusz
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
#pragma once
#include <units/concepts.h>
#include <units/dimension.h>
#include <units/unit.h>
namespace units {
/**
* @brief The type for quantity references
*
* This type is intended to be used in the quantity references definition:
*
* @code{.cpp}
* namespace length_references {
*
* inline constexpr auto m = reference<dim_length, metre>{};
* inline constexpr auto km = reference<dim_length, kilometre>{};
*
* }
*
* namespace references {
*
* using namespace length_references;
*
* }
* @endcode
*
* Quantity references simplify quantity creation:
*
* @code{.cpp}
* using namespace units::isq::si::references;
*
* auto d = 123 * m;
* auto v = 70 * (km / h);
* @endcode
*
* Also, it is allowed to define custom quantity references from existing ones:
*
* @code{.cpp}
* constexpr auto Nm = N * m;
* constexpr auto mph = mi / h;
* @endcode
*
* The following syntaxes are not allowed:
* `2 / s`, `km * 3`, `s / 4`, `70 * km / h`.
*/
template<Dimension auto D, Unit auto U>
struct reference {
static constexpr auto dimension = D;
static constexpr auto unit = U;
};
// Reference
template<Magnitude M, Reference R>
[[nodiscard]] consteval reference<R::dimension, M{} * R::unit> operator*(M, R)
{
return {};
}
template<Reference R1, Reference R2>
[[nodiscard]] consteval reference<R1::dimension * R2::dimension, R1::unit * R2::unit> operator*(R1, R2)
{
return {};
}
template<Reference R1, Reference R2>
[[nodiscard]] consteval reference<R1::dimension / R2::dimension, R1::unit / R2::unit> operator/(R1, R2)
{
return {};
}
template<Representation Rep, Reference R>
[[nodiscard]] constexpr quantity<R{}, Rep> operator*(const Rep& lhs, R)
{
return quantity<R{}, Rep>(lhs);
}
void /*Use `q * (1 * r)` rather than `q * r`.*/ operator*(Quantity auto, Reference auto) = delete;
template<Reference R1, Reference R2>
[[nodiscard]] consteval bool interconvertible(R1, R2)
{
return interconvertible(R1::dimension, R2::dimension) && interconvertible(R1::unit, R2::unit);
}
namespace detail {
[[nodiscard]] consteval auto common_reference(Reference auto r1, Reference auto r2)
requires requires {
{
common_dimension(r1.dimension, r2.dimension)
} -> Dimension;
{
common_unit(r1.unit, r2.unit)
} -> Unit;
}
{
return reference<common_dimension(r1.dimension, r2.dimension), common_unit(r1.unit, r2.unit)>{};
}
} // namespace detail
} // namespace units