interpreter.hpp

深入浅出设计模式（书配套c++源代码)。包含20个设计模式的c++实现。

#ifndef	_HFDP_CPP_INTERPRETER_MINI_DUCK_SIMULATOR_INTERPRETER_HPP_
#define _HFDP_CPP_INTERPRETER_MINI_DUCK_SIMULATOR_INTERPRETER_HPP_

#include "MiniDuckSimulator.hpp"

namespace HeadFirstDesignPatterns {
namespace Interpreter {
namespace MiniDuckSimulator {

class Interpreter : public Visitor {

	private: const Duck* _duck;

	public: explicit Interpreter( const Duck* duck ) :
		_duck( duck ) {
	}
	public: void interpret( DisplayCommand* command ) { assert( command );
		_duck->display();
	}
	public: void interpret( FlyCommand* command ) { assert( command );
		_duck->fly();
	}
	public: void interpret( QuackCommand* command ) { assert( command );
		_duck->quack();
	}
	public: void interpret( SwimCommand* command ) { assert( command );
		_duck->swim();
	}
	public: void interpret( LeftCommand* command ) { assert( command );
		std::cout << "I'm turning left..." << std::endl;
	}
	public: void interpret( RightCommand* command ) { assert( command );
		std::cout << "I'm turning right..." << std::endl;
	}
	public: void interpret( WhileCommand* command ) { assert( command );
		while( true == command->evaluate() ) {
			Context context( command->expression() );
			interpret( context );
		}
	}
	public: void interpret( Context& context ) {
		Expression* expression = context.next();
		for( ; 0 != expression; expression = context.next() ) {
			expression->accept( this );
			delete( expression );
		}
	};
};

} // namespace MiniDuckSimulator
} // namespace Interpreter
} // namespace HeadFirstDesignPatterns

#endif