How to write simple parser for if and while statem

问题:

I need to write a simple parser that will convert the tokens to parser tree. I've already wrote LexicalAnalyzer that returns the tokens. Now, I want to write rules for "if and while" statements(for the beginning), so I could pass this rules to parser and it will create a tree. So i need to write the parser in the way, so I could write new rules.

Can you advise me how I can implement it in C#? Can you give me some example?

回答1:

In a recursive descent parser it's easy to implement these statements if you have the normal block and expression parsers. In pseudo-code, they are basically:

void ParseIf()
{
  Match("if");
  Match("(");
  ParseExpression();
  Match(")");
  ParseBlock();
}

and

void ParseWhile()
{
  Parse("while");
  Parse("(");
  ParseExpression();
  Parse(")");
  ParseBlock();
}