forked from mpusz/mp-units
92 lines
2.8 KiB
C++
92 lines
2.8 KiB
C++
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/*
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Copyright (c) 2003-2020 Andy Little.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see http://www.gnu.org/licenses./
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*/
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#include <units/physical/si/length.h>
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/*
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get conversion factor from one dimensionally equivalent
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quantity type to another
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*/
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namespace {
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template <
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units::Quantity Target,
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units::Quantity Source
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>
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requires units::equivalent_dim<typename Source::dimension,typename Target::dimension>
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constexpr inline
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std::common_type_t<
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typename Target::rep,
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typename Source::rep
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>
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conversion_factor(Target , Source)
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{
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// get quantities looking like inputs but with Q::rep that doesnt have narrowing conversion
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typedef std::common_type_t<
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typename Target::rep,
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typename Source::rep
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> rep;
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typedef units::quantity<typename Source::dimension,typename Source::unit,rep> source;
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typedef units::quantity<typename Target::dimension,typename Target::unit,rep> target;
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return target{source{1}}.count();
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}
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// get at the units text of the quantity, without its numeric value
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auto inline constexpr units_str( units::Quantity const & q)
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{
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typedef std::remove_cvref_t<decltype(q)> qtype;
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return units::detail::unit_text<typename qtype::dimension, typename qtype::unit>();
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}
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}
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namespace {
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namespace length{
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template <typename Rep = double>
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using m = units::si::length<units::si::metre,Rep>;
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template <typename Rep = double>
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using mm = units::si::length<units::si::millimetre,Rep>;
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}
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}
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#include <iostream>
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using namespace units::si::literals;
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int main()
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{
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std::cout << "conversion factor in mpusz/units...\n\n";
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length::m<> constexpr lengthA = 2.0m;
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length::mm<> constexpr lengthB = lengthA;
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std::cout << "lengthA( " << lengthA << " ) and lengthB( " << lengthB << " )\n"
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"represent the same length in different units.\n\n";
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std::cout << "therefore ratio lengthA / lengthB == " << lengthA / lengthB << "\n\n";
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std::cout << "conversion factor from "
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"lengthA::unit of " << units_str(lengthA)
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<< " to lengthB::unit of " << units_str(lengthB) << " :\n\n"
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"lengthB.count( " << lengthB.count() << " ) == "
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"lengthA.count( " << lengthA.count() << " ) * "
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"conversion_factor( " << conversion_factor(lengthB, lengthA) << " )\n";
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}
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