[boost] Re: Interest in a Recursive Descent Parsing Library

From: Joel de Guzman (joel_at_[hidden])
Date: 2004-12-24 18:21:45

christopher diggins wrote:

> struct StartRule {
>  template<typename Elem_T>
>  static bool Accept(ParserInputStream<Elem_T>& in) {
>    switch (in.GetChar()) {
>      case 'a' : return match<RuleA>(in);
>      case 'b' : return match<RuleB>(in);
>      case 'c' : return match<RuleC>(in);
>      case 'd' : return match<RuleD>(in);
>      default : return false;
>    }
>  }
> }
> 
> This approach requires the programmer to figure out the FIRST(N) table 
> by hand. I have found that there are typically only a couple of 
> performance bottlenecks where lookahead is actually needed, and that 
> generating these tables by hand to be easy. Perhaps other's experience 
> is different.
> 
> I would be curious how to express the above grammars in Spirit, with and 
> without the hand-rolled lookahead rule.

See: http://www.boost.org/libs/spirit/doc/switch_parser.html.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net