Examples with an alternate way to create quantities refactored

- examples modified to provide a unified library look-and-feel - originals moved to a dedicated subdirectory for further reference and comparison
2020-03-01 14:44:45 +01:00
parent 0c5864cc87
commit 4b33c0f7c5
10 changed files with 644 additions and 259 deletions
@@ -0,0 +1,79 @@
+/*
+ Copyright (c) 2003-2020 Andy Little.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see http://www.gnu.org/licenses./
+*/
+
+#include <units/physical/si/length.h>
+#include <iostream>
+
+/*
+  get conversion factor from one dimensionally equivalent
+  quantity type to another
+*/
+
+namespace {
+
+template<units::Quantity Target, units::Quantity Source>
+  requires units::equivalent_dim<typename Source::dimension, typename Target::dimension>
+inline constexpr std::common_type_t<typename Target::rep, typename Source::rep> conversion_factor(Target, Source)
+{
+  // get quantities looking like inputs but with Q::rep that doesn't have narrowing conversion
+  typedef std::common_type_t<typename Target::rep, typename Source::rep> rep;
+  typedef units::quantity<typename Source::dimension, typename Source::unit, rep> source;
+  typedef units::quantity<typename Target::dimension, typename Target::unit, rep> target;
+  return target{source{1}}.count();
+}
+
+// get at the units text of the quantity, without its numeric value
+inline auto constexpr units_str(const units::Quantity AUTO& q)
+{
+  typedef std::remove_cvref_t<decltype(q)> qtype;
+  return units::detail::unit_text<typename qtype::dimension, typename qtype::unit>();
+}
+
+}  // namespace
+
+namespace {
+
+namespace length {
+
+template<typename Rep = double>
+using m = units::si::length<units::si::metre, Rep>;
+
+template<typename Rep = double>
+using mm = units::si::length<units::si::millimetre, Rep>;
+
+}  // namespace length
+}  // namespace
+
+using namespace units::si::literals;
+
+int main()
+{
+  std::cout << "conversion factor in mpusz/units...\n\n";
+
+  constexpr length::m<> lengthA = 2.0q_m;
+  constexpr length::mm<> lengthB = lengthA;
+
+  std::cout << "lengthA( " << lengthA << " ) and lengthB( " << lengthB << " )\n"
+            << "represent the same length in different units.\n\n";
+
+  std::cout << "therefore ratio lengthA / lengthB == " << lengthA / lengthB << "\n\n";
+
+  std::cout << "conversion factor from lengthA::unit of "
+            << units_str(lengthA) << " to lengthB::unit of " << units_str(lengthB) << " :\n\n"
+            << "lengthB.count( " << lengthB.count() << " ) == lengthA.count( " << lengthA.count()
+            << " ) * conversion_factor( " << conversion_factor(lengthB, lengthA) << " )\n";
+}