Metaprogramming.h

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/*
 * Copyright (c) 2018-2019 pongasoft
 *
 * Licensed under the Apache License, Version 2.0 or the MIT license,
 * at your option. You may not use this file except in compliance with
 * one of these licenses. You may obtain copies of the licenses at:
 *
 * https://www.apache.org/licenses/LICENSE-2.0
 * https://opensource.org/licenses/MIT
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 *
 * @author Yan Pujante
 */
#pragma once
 
#include <sstream>
#include <ostream>
#include <concepts>
 
namespace pongasoft::Utils {
 
template<typename To, typename From>
concept DynamicCastablePointer =
  std::is_pointer_v<To> &&
  requires(From* p)
{
  dynamic_cast<To>(p);
};

template<typename To, typename From>
requires std::is_pointer_v<To>
constexpr To safe_dynamic_cast(From* p) noexcept
{
  if constexpr (DynamicCastablePointer<To, From>)
    return dynamic_cast<To>(p);
  else
    return nullptr;
}

template<typename T>
concept HasNotEqual =
  requires(T const &a, T const &b)
  {
    { a != b } -> std::convertible_to<bool>;
  };

template<typename From, typename To>
concept ConvertibleTo =
  requires(From const& f)
  {
    { static_cast<To>(f) } -> std::same_as<To>;
  };

template<typename T>
concept OstreamWritable =
  requires(std::ostream& os, T const& t)
  {
    { os << t } -> std::same_as<std::ostream&>;
  };

template<typename T>
std::string typeString()
{
  std::stringstream s;
  s << typeid(T).name();
  if constexpr (std::is_const_v<typename std::remove_reference<T>::type>)
    s << " const";
  if constexpr (std::is_reference_v<T>)
    s << " &";
  return s.str();
}
 
}