forked from mpusz/mp-units
9527b39005
We had some fun exploring the STD UDLs for potential collisions, we have learnt our lesson and know how to proceed. Now is high time to start behaving and obeying C++ rules.
60 lines
2.2 KiB
C++
60 lines
2.2 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 <units/format.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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} // namespace
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int main()
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{
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using namespace units::physical::si;
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std::cout << "conversion factor in mp-units...\n\n";
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constexpr length<metre> lengthA = 2.0_q_m;
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constexpr length<millimetre> lengthB = lengthA;
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std::cout << 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 << fmt::format("therefore ratio lengthA / lengthB == {}\n\n", lengthA / lengthB);
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std::cout << fmt::format("conversion factor from lengthA::unit of {:%q} to lengthB::unit of {:%q}:\n\n", lengthA, lengthB)
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<< fmt::format("lengthB.count( {} ) == lengthA.count( {} ) * conversion_factor( {} )\n",
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lengthB.count(), lengthA.count(), conversion_factor(lengthB, lengthA));
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}
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