add constexpr containers (#187)

example/example_containers_set.cpp

@@ -0,0 +1,55 @@
+// Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2019 - 2022 Daniil Goncharov <neargye@gmail.com>.
+//
+// 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.
+
+#if defined(_MSC_VER)
+#  pragma warning(push)
+#  pragma warning(disable : 4244) // warning C4244: 'argument': conversion from 'const T' to 'unsigned int', possible loss of data.
+#endif
+
+#ifdef _WIN32
+#define _ITERATOR_DEBUG_LEVEL 0
+#endif
+
+#include <iostream>
+
+#include <magic_enum_containers.hpp>
+
+enum class Color { RED = 1, GREEN = 2, BLUE = 4 };
+
+int main() {
+
+  std::cout << std::boolalpha;
+  magic_enum::containers::set color_set {Color::RED, Color::GREEN, Color::BLUE};
+  std::cout << color_set.empty() << std::endl; // false
+  std::cout << color_set.size() << std::endl; // 3
+
+  color_set.clear();
+  std::cout << color_set.empty() << std::endl; // true
+  std::cout << color_set.size() << std::endl; // 0
+
+  color_set.insert(Color::GREEN);
+  color_set.insert(Color::BLUE);
+  std::cout << color_set.empty() << std::endl; // false
+  std::cout << color_set.size() << std::endl; // 2
+
+  return 0;
+}