if_then_else_expression.hpp

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#pragma once
#include "as_expression.hpp"
#include "conditional_expression.hpp"
#include "expression_operand.hpp"
#include "expression_stream.hpp"
#include <utility>

namespace xtd {
  namespace expressions {
    template <typename condition_t, typename then_t, typename else_t>
    struct if_then_else_expression : conditional_expression {
      
      static constexpr operator_precedence precedence = operator_precedence::ternary;
      
      
      constexpr if_then_else_expression() = default;
      
      constexpr if_then_else_expression(condition_t condition, then_t then_, else_t else_) : condition(std::move(condition)), then_(std::move(then_)), else_(std::move(else_)) {}
      
      
      template <typename... args_t>
      constexpr auto operator()(args_t&&... args) const {return condition(args...) ? then_(args...) : else_(args...);}
      
      friend inline auto operator <<(std::ostream& os, const if_then_else_expression& e) -> std::ostream& {return os << expression_stream {e.condition, e.precedence} << " ? " << expression_stream {e.then_, e.precedence} << " : " << expression_stream {e.else_, e.precedence};}
      
    private:
      [[no_unique_address]] condition_t condition;
      [[no_unique_address]] then_t then_;
      [[no_unique_address]] else_t else_;
    };

    
    template <typename condition_t, typename then_t, typename else_t>
    requires expression_operand<condition_t> || expression_operand<then_t> || expression_operand<else_t>
    constexpr auto if_then_else(condition_t condition, then_t then_, else_t else_) {
      auto condition_expression = as_expression(condition);
      auto then_expression = as_expression(then_);
      auto else_expression = as_expression(else_);
      return if_then_else_expression<std::decay_t<decltype(condition_expression)>, std::decay_t<decltype(then_expression)>, std::decay_t<decltype(else_expression)>> {std::move(condition_expression), std::move(then_expression), std::move(else_expression)};
    }

  }
}