[antlr-interest] "An Introduction to ANTLR" presentation slides
Matt Benson
gudnabrsam at yahoo.com
Wed Feb 27 13:22:39 PST 2008
--- Terence Parr <parrt at cs.usfca.edu> wrote:
>
> On Feb 27, 2008, at 12:45 PM, Andy Tripp wrote:
>
> > Hi Matt,
> >
> > Thanks. Yea, I was very hesitant to put that
> sentence in, as I
> > wasn't sure it was
> > correct. I'd appreciate it if anyone could clarify
> this for me.
>
> hi gang. A semantic predicate is a boolean
> expression that must be
> true for the parse to pass over it; any kind of
> recognizer. A gated
> sem pred is one that forces alts to be turned on or
> off at run time.
>
> A syn pred simply specifies the sytnactic context
> that must be true
> for the parser (or lexer or tree parser) to pass.
> I.e., if you see X,
> then Y will match:
>
> a : (X)=> Y
> | ...
> ;
>
Wait--is that example literal? In rule a, how could
next token X predict Y? I -had- thought I understood
the syntactic predicate. :(
-Matt
> preds order the alts. first one that matches wins.
>
> Ter
> >
> >
> > Andy
> >
> > Matt Benson wrote:
> >>
> >> Syntactic Predicate" is just some "Symantic
> >> Predicate" that happens to be in a lexer
> >> rule rather than a parser rule.
> >>
> >>
> >
>
>
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