forked from mpusz/mp-units
62 lines
2.3 KiB
C++
62 lines
2.3 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/format.h>
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#include <units/isq/si/length.h>
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#include <iostream>
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#include <type_traits>
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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<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}}.number();
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}
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} // namespace
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int main()
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{
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using namespace units::isq::si;
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std::cout << "conversion factor in mp-units...\n\n";
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constexpr length<metre> lengthA(2.0);
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constexpr length<millimetre> lengthB = lengthA;
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std::cout << STD_FMT::format("lengthA( {} ) and lengthB( {} )\n", lengthA, lengthB)
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<< "represent the same length in different units.\n\n";
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std::cout << STD_FMT::format("therefore ratio lengthA / lengthB == {}\n\n", lengthA / lengthB);
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std::cout << STD_FMT::format("conversion factor from lengthA::unit of {:%q} to lengthB::unit of {:%q}:\n\n", lengthA,
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lengthB)
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<< STD_FMT::format("lengthB.number( {} ) == lengthA.number( {} ) * conversion_factor( {} )\n",
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lengthB.number(), lengthA.number(), conversion_factor(lengthB, lengthA));
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}
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