An Introduction to the Boost Spirit Parser framework

#pragma once

#include <boost/spirit.hpp>
#include <string>
#include <exception>

namespace Calculator
{
	class CParser;
	namespace Private
	{
		////////////////////////////////////////////////////////////////////////////////
		///	A set of functors that are used as callbacks from within the parser framework
		///
		////////////////////////////////////////////////////////////////////////////////
		struct FinishedProcessing
		{
		public:
			FinishedProcessing( CParser &parser ) : m_parser( parser ) {}
			template <typename IteratorT>
			void operator()( IteratorT, IteratorT ) const
			{
				m_parser.SetProcessingFinished();
			}
			template <typename CharT>
			void operator()( CharT ) const
			{
				m_parser.SetProcessingFinished();
			}
		private:
			CParser &m_parser;
		};
	}	// namespace Private

	////////////////////////////////////////////////////////////////////////////////
	///	The syntax, defined according to specific boost::spirit	requirements
	///
	////////////////////////////////////////////////////////////////////////////////
	struct Syntax :
		public boost::spirit::grammar<Syntax>
	{
	public:
		Syntax( CParser &parser );
		virtual ~Syntax();
		template <typename ScannerT>
		struct definition
		{
		public:
			definition( Syntax const &self )
			{
				integer =
					lexeme_d[ (+digit_p) ]
					;
				factor =
					integer |
					vars |
					'(' >> expression >> ')' |
					( '-' >> factor ) |
					( '+' >> factor )
					;
				term =
					factor >> *( ( '*' >> factor) | ( '/' >> factor ) )
					;
				expression =
					term >> *( ( '+' >> term ) | ( '-' >> term ) )
					;
				assignment =
					vars
					>> '=' >> expression
					;
				var_decl =
					lexeme_d
					[
						( ( alpha_p >> *( alnum_p | '_' ) )
						- vars )[vars.add]
					]
					;
				declaration =
					"int" >> var_decl >> *( ',' >> var_decl )
					;
				baseExpression =
					str_p( "exit" )[*self.m_finishedProcessing] |
					str_p( "mod" ) >> integer |
					declaration |
					assignment |
					'?' >> expression
					;
			}
			boost::spirit::symbols<int> vars;
			boost::spirit::rule<ScannerT> integer, factor, term,
				expression, assignment, var_decl, declaration,
				baseExpression;
			const boost::spirit::rule<ScannerT> &start() const { return baseExpression; }
		};
		friend struct definition;
	private:
		Private::FinishedProcessing *m_finishedProcessing;
	};

}	// namespace Calculator