ParseLib

.NET library that provides components for dynamic parsers generation.

Features

• End-to-end solution with a built-in lexical analyzer.
• Fluent Regular Expressions building interface.
• LALR(1) grammars with a flexible conflicts handling mechanism.
• Unicode support.
• In-memory dynamic type generation.
• Async sequential parser implementation out-of-the-box.

For more information check the project's wiki page or examine the samples folder.

Usage Sample

First, we need to configure a grammar itself. For sample code we will define a single number terminal and a set of rules for basic math operations:

vardigit=Rex.Char("0-9");vargrammar=newGrammar();grammar.CreateTerminals("+","-","/","*","(",")");grammar.CreateNonTerminals("expr");grammar.CreateWhitespace("ws",Rex.Char(' ').OneOrMore());grammar.CreateTerminal("expr:num",digit.OneOrMore());grammar.AddRule("expr:unary","- expr").ReduceOn("*","/","+","-");grammar.AddRule("expr:add","expr + expr").ReduceOn("+","-").ShiftOn("*","/");grammar.AddRule("expr:sub","expr - expr").ReduceOn("+","-").ShiftOn("*","/");grammar.AddRule("expr:mul","expr * expr").ReduceOn("*","/","+","-");grammar.AddRule("expr:div","expr / expr").ReduceOn("*","/","+","-");grammar.AddRule("expr:group","( expr )");

Then, we need a user-defined parser class where handers for the grammar tokens and rules are implemented. The parser also determines a target type of the output:

publicabstractclassExpressionParser:StringParser{publicExpressionParser(stringexpression):base(expression){}[CompleteToken("num")]publicintCompleteNumber()=>Int32.Parse(GetLexeme());[Reduce("expr:add")]publicintAdd(intx,inty)=>x+y;[Reduce("expr:sub")]publicintSub(intx,inty)=>x-y;[Reduce("expr:mul")]publicintMul(intx,inty)=>x*y;[Reduce("expr:div")]publicintDiv(intx,inty)=>x/y;[Reduce("expr:unary")]publicintNegate(intx)=>-x;}

Finally, based on the grammar and the parser we can build a parser factory. The factory is just a wrapper for an appropriate constructor defined by a type of the parser was generated:

varfactory=grammar.CreateStringParserFactory<ExpressionParser>("expr");varparser=factory("-2 + -(2 * 2)");parser.Parse();Console.WriteLine(parser.GetResult());