refactor: capacitor_time_curve refactored for V2

example/capacitor_time_curve.cpp

@@ -0,0 +1,59 @@
+/*
+ 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./
+*/
+
+/*
+    capacitor discharge curve using compile_time
+    physical_quantities
+*/
+
+#include <units/isq/electromagnetism.h>
+#include <units/math.h>  // IWYU pragma: keep
+#include <units/quantity_io.h>
+#include <units/si/si.h>
+#include <iostream>
+
+int main()
+{
+  using namespace units;
+  using namespace units::si::unit_symbols;
+
+  std::cout << "mp-units capacitor time curve example...\n";
+  std::cout.setf(std::ios_base::fixed, std::ios_base::floatfield);
+  std::cout.precision(3);
+
+  constexpr auto C = 0.47 * isq::capacitance[uF];
+  constexpr auto V0 = 5.0 * isq::voltage[V];
+  constexpr auto R = 4.7 * isq::resistance[si::kilo<si::ohm>];
+
+  for (auto t = 0 * isq::time[ms]; t <= 50 * isq::time[ms]; ++t) {
+    const weak_quantity_of<isq::voltage> auto Vt = V0 * units::exp(-t / (R * C));
+
+    std::cout << "at " << t << " voltage is ";
+
+    if (Vt >= 1 * isq::voltage[V])
+      std::cout << Vt[V];
+    else if (Vt >= 1 * isq::voltage[mV])
+      std::cout << Vt[mV];
+    else if (Vt >= 1 * isq::voltage[uV])
+      std::cout << Vt[uV];
+    else if (Vt >= 1 * isq::voltage[nV])
+      std::cout << Vt[nV];
+    else
+      std::cout << Vt[pV];
+    std::cout << "\n";
+  }
+}