refactor(example): avg_speed example refactored for V2

example/avg_speed.cpp

@@ -0,0 +1,166 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#include <units/isq/space_and_time.h>
+#include <units/quantity_io.h>
+#include <units/si/cgs/cgs.h>
+#include <units/si/international/length.h>
+#include <units/si/unit_symbols.h>
+#include <exception>
+#include <iostream>
+
+namespace {
+
+using namespace units;
+using namespace units::si::unit_symbols;
+
+constexpr quantity<isq::speed[m / s], int> fixed_int_si_avg_speed(quantity<isq::length[m], int> d,
+                                                                  quantity<isq::time[s], int> t)
+{
+  return d / t;
+}
+
+constexpr quantity<isq::speed[m / s]> fixed_double_si_avg_speed(quantity<isq::length[m]> d, quantity<isq::time[s]> t)
+{
+  return d / t;
+}
+
+constexpr quantity_of<isq::speed> auto avg_speed(quantity_of<isq::length> auto d, quantity_of<isq::time> auto t)
+{
+  return quantity_cast<isq::speed>(d / t);
+}
+
+template<quantity_of<isq::length> D, quantity_of<isq::time> T, quantity_of<isq::speed> V>
+void print_result(D distance, T duration, V speed)
+{
+  const auto result_in_kmph = quantity_cast<km / h>(speed);
+  std::cout << "Average speed of a car that makes " << distance << " in " << duration << " is " << result_in_kmph
+            << ".\n";
+}
+
+void example()
+{
+  // SI (int)
+  {
+    constexpr auto distance = 220 * isq::length[km];
+    constexpr auto duration = 2 * isq::time[h];
+
+    std::cout << "SI units with 'int' as representation\n";
+
+    print_result(distance, duration, fixed_int_si_avg_speed(distance, duration));
+    print_result(distance, duration, fixed_double_si_avg_speed(distance, duration));
+    print_result(distance, duration, avg_speed(distance, duration));
+  }
+
+  // SI (double)
+  {
+    constexpr auto distance = 220. * isq::length[km];
+    constexpr auto duration = 2. * isq::time[h];
+
+    std::cout << "\nSI units with 'double' as representation\n";
+
+    // conversion from a floating-point to an integral type is a truncating one so an explicit cast is needed
+    print_result(distance, duration,
+                 fixed_int_si_avg_speed(quantity_cast<int>(distance), quantity_cast<int>(duration)));
+    print_result(distance, duration, fixed_double_si_avg_speed(distance, duration));
+    print_result(distance, duration, avg_speed(distance, duration));
+  }
+
+  // Customary Units (int)
+  {
+    using namespace units::si::international::unit_symbols;
+
+    constexpr auto distance = 140 * isq::length[mi];
+    constexpr auto duration = 2 * isq::time[h];
+
+    std::cout << "\nUS Customary Units with 'int' as representation\n";
+
+    // it is not possible to make a lossless conversion of miles to meters on an integral type
+    // (explicit cast needed)
+    print_result(distance, duration, fixed_int_si_avg_speed(quantity_cast<si::metre>(distance), duration));
+    print_result(distance, duration, fixed_double_si_avg_speed(distance, duration));
+    print_result(distance, duration, avg_speed(distance, duration));
+  }
+
+  // Customary Units (double)
+  {
+    using namespace units::si::international::unit_symbols;
+    constexpr auto distance = 140. * isq::length[mi];
+    constexpr auto duration = 2. * isq::time[h];
+
+    std::cout << "\nUS Customary Units with 'double' as representation\n";
+
+    // conversion from a floating-point to an integral type is a truncating one so an explicit cast is needed
+    // also it is not possible to make a lossless conversion of miles to meters on an integral type
+    // (explicit cast needed)
+    print_result(
+      distance, duration,
+      fixed_int_si_avg_speed(quantity_cast<quantity<isq::length[m], int>>(distance), quantity_cast<int>(duration)));
+    print_result(distance, duration, fixed_double_si_avg_speed(distance, duration));
+    print_result(distance, duration, avg_speed(distance, duration));
+  }
+
+  // CGS (int)
+  {
+    constexpr auto distance = 22'000'000 * isq::length[si::cgs::centimetre];
+    constexpr auto duration = 7200 * isq::time[si::cgs::second];
+
+    std::cout << "\nCGS units with 'int' as representation\n";
+
+    // it is not possible to make a lossless conversion of centimeters to meters on an integral type
+    // (explicit cast needed)
+    print_result(distance, duration, fixed_int_si_avg_speed(quantity_cast<si::metre>(distance), duration));
+    print_result(distance, duration, fixed_double_si_avg_speed(distance, duration));
+    print_result(distance, duration, avg_speed(distance, duration));
+  }
+
+  // CGS (double)
+  {
+    constexpr auto distance = 22'000'000. * isq::length[si::cgs::centimetre];
+    constexpr auto duration = 7200. * isq::time[si::cgs::second];
+
+    std::cout << "\nCGS units with 'double' as representation\n";
+
+    // conversion from a floating-point to an integral type is a truncating one so an explicit cast is needed
+    // it is not possible to make a lossless conversion of centimeters to meters on an integral type
+    // (explicit cast needed)
+    print_result(
+      distance, duration,
+      fixed_int_si_avg_speed(quantity_cast<quantity<isq::length[m], int>>(distance), quantity_cast<int>(duration)));
+
+    print_result(distance, duration, fixed_double_si_avg_speed(distance, duration));
+    print_result(distance, duration, avg_speed(distance, duration));
+  }
+}
+
+}  // namespace
+
+int main()
+{
+  try {
+    example();
+  } catch (const std::exception& ex) {
+    std::cerr << "Unhandled std exception caught: " << ex.what() << '\n';
+  } catch (...) {
+    std::cerr << "Unhandled unknown exception caught\n";
+  }
+}