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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

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