Parsing Expression Grammar Support for C# 3.0 Part 1 - PEG Lib and Parser Generator

<<Grammar >>
top{ // semantic top level block using C# as host language
  internal double result;
  internal bool print_(){Console.WriteLine("{0}",result);return true;}
}
Expr:    S Sum   (!. print_ / FATAL<"following code not recognized">)				;
Sum
{  //semantic rule related block using C# as host language (block can be implemented as nested struct)
        internal _Sum(calc0_direct parent){parent_=parent;}
        calc0_direct parent_;
	double v;
  	internal bool save_(){v= parent_.top.result;parent_.top.result=0; return true;}
	internal bool add_() {v+= parent_.top.result;parent_.top.result=0;return true;}
	internal bool sub_() {v-= parent_.top.result;parent_.top.result=0;return true;} 
  	internal bool store_(){parent_.top.result= v; return true;}
}	:     
	Product save_
                ('+' S Product add_
		/'-' S Product sub_)* store_		;
Product
{ //semantic rule related block using C# as host language (block can be implemented as nested struct)
        internal _Product(calc0_direct parent){parent_=parent;}
        calc0_direct parent_;
	double v;
	internal bool save_(){v= parent_.top.result;parent_.top.result=0; return true;}
	internal bool mul_(){v*= parent_.top.result;parent_.top.result=0; return true;}
	internal bool div_(){v/= parent_.top.result;parent_.top.result=0;return true;} 
	internal bool store_(){parent_.top.result= v;return true;}	
}	: 
	Value  save_
	        ('*' S Value mul_
		/'/' S Value div_)* store_		;  
Value:   Number S / '(' S Sum ')' S	;
Number
{ //semantic rule related block using C# as host language (block can be implemented as nested struct)
        internal _Number(calc0_direct parent){parent_=parent;}
        calc0_direct parent_;
	internal string sNumber;
	internal bool store_(){double.TryParse(sNumber,out parent_.top.result);return true;}
}
	:  ([0-9]+ ('.' [0-9]+)?):sNumber store_	;
S:	 [ \n\r\t\v]*					;
<</Grammar>>