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mp-units/src/include/units/quantity_cast.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/customization_points.h>
#include <units/bits/dimension_op.h>
#include <units/bits/external/type_traits.h>
#include <cassert>
namespace units {
constexpr std::intmax_t ipow10(std::intmax_t exp)
{
assert(exp >= 0);
if (exp == 0) return 1;
std::intmax_t result = 1;
while (exp > 0) {
result *= 10;
--exp;
}
return result;
}
constexpr long double fpow10(std::intmax_t exp)
{
if (exp == 0) return 1.0L;
long double result = 1.0L;
if (exp < 0) {
while (exp < 0) {
result /= 10.0L;
++exp;
}
} else {
while (exp > 0) {
result *= 10.0L;
--exp;
}
}
return result;
}
// QuantityOf
template<typename T, typename Dim>
concept QuantityOf = Quantity<T> && Dimension<Dim> && equivalent_dim<typename T::dimension, Dim>;
// quantity_cast
namespace detail {
template<typename To, typename CRatio, typename CRep, bool NumIsOne, bool DenIsOne, bool ExpIsZero>
struct quantity_cast_impl;
template<typename To, typename CRatio, typename CRep>
struct quantity_cast_impl<To, CRatio, CRep, true, true, true> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
return To(static_cast<To::rep>(q.count()));
}
};
template<typename To, typename CRatio, constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, true, true, false> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(fpow10(CRatio::exp))));
} else {
if constexpr (CRatio::exp > 0) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(ipow10(CRatio::exp))));
}
else {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) / static_cast<CRep>(ipow10(-CRatio::exp))));
}
}
}
};
template<typename To, typename CRatio, constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, false, false, true> {
template<typename Q>
static constexpr To cast(const Q& q)
{
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) *
(static_cast<CRep>(CRatio::num) /
static_cast<CRep>(CRatio::den))));
}
};
template<typename To, typename CRatio, constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, false, false, false> {
template<typename Q>
static constexpr To cast(const Q& q)
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) *
static_cast<CRep>(fpow10(CRatio::exp)) *
(static_cast<CRep>(CRatio::num) /
static_cast<CRep>(CRatio::den))));
} else {
if constexpr (CRatio::exp > 0) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) *
static_cast<CRep>(CRatio::num) *
static_cast<CRep>(ipow10(CRatio::exp)) /
static_cast<CRep>(CRatio::den)));
}
else {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) *
static_cast<CRep>(CRatio::num) /
(static_cast<CRep>(CRatio::den) *
static_cast<CRep>(ipow10(-CRatio::exp)))));
}
}
}
};
template<typename To, typename CRatio, constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, true, false, true> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) / static_cast<CRep>(CRatio::den)));
}
};
template<typename To, typename CRatio, constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, true, false, false> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(fpow10(CRatio::exp)) * (CRep{1} / static_cast<CRep>(CRatio::den))));
} else {
if constexpr (CRatio::exp > 0) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(ipow10(CRatio::exp)) / static_cast<CRep>(CRatio::den)));
}
else {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) / (static_cast<CRep>(ipow10(-CRatio::exp)) * static_cast<CRep>(CRatio::den))));
}
}
}
};
template<typename To, typename CRatio, constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, false, true, true> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CRatio::num)));
}
};
template<typename To, typename CRatio, constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, false, true, false> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CRatio::num) * static_cast<CRep>(fpow10(CRatio::exp))));
} else {
if constexpr (CRatio::exp > 0) {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CRatio::num) * static_cast<CRep>(ipow10(CRatio::exp))));
}
else {
return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CRatio::num) / static_cast<CRep>(ipow10(-CRatio::exp))));
}
}
}
};
template<typename To, typename CRatio, not_constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, true, true, false> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(q.count() * fpow10(CRatio::exp)));
} else {
if constexpr (CRatio::exp > 0) {
return To(static_cast<To::rep>(q.count() * ipow10(CRatio::exp)));
}
else {
return To(static_cast<To::rep>(q.count() / ipow10(-CRatio::exp)));
}
}
}
};
template<typename To, typename CRatio, not_constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, false, false, true> {
template<typename Q>
static constexpr To cast(const Q& q)
{
return To(static_cast<To::rep>(q.count() * (CRatio::num / CRatio::den)));
}
};
template<typename To, typename CRatio, not_constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, false, false, false> {
template<typename Q>
static constexpr To cast(const Q& q)
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(q.count() * fpow10(CRatio::exp) * (CRatio::num / CRatio::den)));
} else {
if constexpr (CRatio::exp > 0) {
return To(static_cast<To::rep>(q.count() * CRatio::num * ipow10(CRatio::exp) / CRatio::den));
}
else {
return To(static_cast<To::rep>(q.count()) * CRatio::num / (CRatio::den * ipow10(-CRatio::exp)));
}
}
}
};
template<typename To, typename CRatio, not_constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, true, false, true> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
return To(static_cast<To::rep>(q.count() / CRatio::den));
}
};
template<typename To, typename CRatio, not_constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, true, false, false> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(q.count() * fpow10(CRatio::exp) / CRatio::den));
} else {
if constexpr (CRatio::exp > 0) {
return To(static_cast<To::rep>(q.count() * ipow10(CRatio::exp) / CRatio::den));
}
else {
return To(static_cast<To::rep>(q.count() / (ipow10(-CRatio::exp) * CRatio::den)));
}
}
}
};
template<typename To, typename CRatio, not_constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, false, true, true> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
return To(static_cast<To::rep>(q.count() * CRatio::num));
}
};
template<typename To, typename CRatio, not_constructible_from_integral CRep>
struct quantity_cast_impl<To, CRatio, CRep, false, true, false> {
template<Quantity Q>
static constexpr To cast(const Q& q)
{
if constexpr (treat_as_floating_point<CRep>) {
return To(static_cast<To::rep>(q.count() * CRatio::num * fpow10(CRatio::exp)));
} else {
if constexpr (CRatio::exp > 0) {
return To(static_cast<To::rep>(q.count() * CRatio::num * ipow10(CRatio::exp)));
}
else {
return To(static_cast<To::rep>(q.count() * CRatio::num / ipow10(-CRatio::exp)));
}
}
}
};
template<Dimension FromD, Unit FromU, Dimension ToD, Unit ToU>
struct cast_ratio;
template<BaseDimension FromD, Unit FromU, BaseDimension ToD, Unit ToU>
struct cast_ratio<FromD, FromU, ToD, ToU> {
using type = ratio_divide<typename FromU::ratio, typename ToU::ratio>;
};
template<DerivedDimension FromD, Unit FromU, DerivedDimension ToD, Unit ToU>
requires same_unit_reference<FromU, ToU>::value
struct cast_ratio<FromD, FromU, ToD, ToU> {
using type = ratio_divide<typename FromU::ratio, typename ToU::ratio>;
};
template<DerivedDimension FromD, Unit FromU, DerivedDimension ToD, Unit ToU>
struct cast_ratio<FromD, FromU, ToD, ToU> {
using from_ratio = ratio_multiply<typename FromD::base_units_ratio, typename FromU::ratio>;
using to_ratio = ratio_multiply<typename ToD::base_units_ratio, typename ToU::ratio>;
using type = ratio_divide<from_ratio, to_ratio>;
};
} // namespace detail
/**
* @brief Explcit cast of a quantity
*
* Implicit conversions between quantities of different types are allowed only for "safe"
* (i.e. non-truncating) conversion. In such cases an explicit cast have to be used.
*
* This cast gets the target quantity type to cast to. For example:
*
* auto q1 = units::quantity_cast<units::physical::si::time<units::physical::si::second>>(1q_ms);
*
* @tparam To a target quantity type to cast to
*/
template<Quantity To, typename D, typename U, typename Rep>
[[nodiscard]] constexpr auto quantity_cast(const quantity<D, U, Rep>& q)
requires QuantityOf<To, D>
{
using c_ratio = detail::cast_ratio<D, U, typename To::dimension, typename To::unit>::type;
using c_rep = std::common_type_t<typename To::rep, Rep>;
using ret_unit = downcast_unit<typename To::dimension, typename To::unit::ratio>;
using ret = quantity<typename To::dimension, ret_unit, typename To::rep>;
using cast = detail::quantity_cast_impl<ret, c_ratio, c_rep, c_ratio::num == 1, c_ratio::den == 1, c_ratio::exp == 0>;
return cast::cast(q);
}
/**
* @brief Explcit cast of a quantity
*
* Implicit conversions between quantities of different types are allowed only for "safe"
* (i.e. non-truncating) conversion. In such cases an explicit cast have to be used.
*
* This cast gets only the target dimension to cast to. For example:
*
* auto q1 = units::quantity_cast<units::physical::si::acceleration>(200q_Gal);
*
* @tparam ToD a dimension type to use for a target quantity
*/
template<Dimension ToD, typename D, typename U, typename Rep>
[[nodiscard]] constexpr auto quantity_cast(const quantity<D, U, Rep>& q)
requires equivalent_dim<ToD, D>
{
return quantity_cast<quantity<ToD, dimension_unit<ToD>, Rep>>(q);
}
/**
* @brief Explcit cast of a quantity
*
* Implicit conversions between quantities of different types are allowed only for "safe"
* (i.e. non-truncating) conversion. In such cases an explicit cast have to be used.
*
* This cast gets only the target unit to cast to. For example:
*
* auto q1 = units::quantity_cast<units::physical::si::second>(1q_ms);
*
* @tparam ToU a unit type to use for a target quantity
*/
template<Unit ToU, typename D, typename U, typename Rep>
[[nodiscard]] constexpr auto quantity_cast(const quantity<D, U, Rep>& q)
requires UnitOf<ToU, D>
{
return quantity_cast<quantity<D, ToU, Rep>>(q);
}
/**
* @brief Explcit cast of a quantity
*
* Implicit conversions between quantities of different types are allowed only for "safe"
* (i.e. non-truncating) conversion. In such cases an explicit cast have to be used.
*
* This cast gets only representation to cast to. For example:
*
* auto q1 = units::quantity_cast<int>(1q_ms);
*
* @tparam ToRep a representation type to use for a target quantity
*/
template<Scalar ToRep, typename D, typename U, typename Rep>
[[nodiscard]] constexpr auto quantity_cast(const quantity<D, U, Rep>& q)
{
return quantity_cast<quantity<D, U, ToRep>>(q);
}
/**
* @brief Explcit cast of a quantity point
*
* Implicit conversions between quantity points of different types are allowed only for "safe"
* (i.e. non-truncating) conversion. In other cases an explicit cast has to be used.
*
* This cast gets the target quantity point type to cast to or anything that works for quantity_cast. For example:
*
* auto q1 = units::quantity_point_cast<decltype(quantity_point{0q_s})>(quantity_point{1q_ms});
* auto q1 = units::quantity_point_cast<units::physical::si::time<units::physical::si::second>>(quantity_point{1q_ms});
* auto q1 = units::quantity_point_cast<units::physical::si::acceleration>(quantity_point{200q_Gal});
* auto q1 = units::quantity_point_cast<units::physical::si::second>(quantity_point{1q_ms});
* auto q1 = units::quantity_point_cast<int>(quantity_point{1q_ms});
*
* @tparam CastSpec a target quantity point type to cast to or anything that works for quantity_cast
*/
template<typename CastSpec, typename D, typename U, typename Rep>
[[nodiscard]] constexpr auto quantity_point_cast(const quantity_point<D, U, Rep>& qp)
requires is_instantiation<CastSpec, quantity_point> ||
requires(quantity<D, U, Rep> q) { quantity_cast<CastSpec>(q); }
{
if constexpr (is_instantiation<CastSpec, quantity_point>)
return quantity_point(quantity_cast<typename CastSpec::quantity_type>(qp.relative()));
else
return quantity_point(quantity_cast<CastSpec>(qp.relative()));
}
} // namespace units