forked from mpusz/mp-units
80 lines
2.7 KiB
C++
80 lines
2.7 KiB
C++
/*
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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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#include <iostream>
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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<units::Quantity Target, units::Quantity Source>
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requires units::equivalent_dim<typename Source::dimension, typename Target::dimension>
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inline constexpr std::common_type_t<typename Target::rep, typename Source::rep> conversion_factor(Target, Source)
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{
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// get quantities looking like inputs but with Q::rep that doesn't have narrowing conversion
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typedef std::common_type_t<typename Target::rep, typename Source::rep> 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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inline auto constexpr units_str(const units::Quantity AUTO& 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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} // namespace
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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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} // namespace length
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} // namespace
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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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constexpr length::m<> lengthA = 2.0m;
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constexpr length::mm<> 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 lengthA::unit of "
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<< units_str(lengthA) << " to lengthB::unit of " << units_str(lengthB) << " :\n\n"
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<< "lengthB.count( " << lengthB.count() << " ) == lengthA.count( " << lengthA.count()
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<< " ) * conversion_factor( " << conversion_factor(lengthB, lengthA) << " )\n";
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}
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