A major and remarquable change / JD. Le mercredi 19 février 2014 19:37:33 UTC+1, Jeffrey Kegler a écrit : > > I've just uploaded 2.080000, a new indexed > version<https://metacpan.org/release/JKEGL/Marpa-R2-2.080000>, > to CPAN. This release > is a very big change internally, the first external sign of which is > the introduction of efficient Longest Acceptable Tokens Matching (LATM) > to the SLIF. LATM is implemented using the "forgiving > adverb"<https://metacpan.org/pod/release/JKEGL/Marpa-R2-2.080000/pod/Scanless/DSL.pod#forgiving> > . > > LATM means that the SLIF, when lexing, considers only those tokens > that would actually be acceptable to the top-level structural grammar. > Previously, the SLIF used Longet Tokens Matching (LTM), and considered > all lexemes, even those that would not be acceptable to the parse. > LTM is the tradition and the current standard practice in parsing -- > pre-Marpa parsers are not smart enough to tell lexers which lexemes they > can accept and which they cannot. > > LATM is "smarter" than LTM. This "smartness" allows you to be more > aggressive in designing your lexer -- it increases the likelihood that > the parser will know "what you meant". When context is used to help make > the decision, the chance that two of your tokens will treat the same > input string in conflicting ways is reduced. With LATM, unacceptable > tokens will not cause conflicts. > > LATM is not the default, because of backward compatibility. But I > recommend that everyone, as their preferred choice, start all new > scripts with > > lexeme default = forgiving => 1 > > > You also should be able to convert most old scripts to use LATM without a > problem, making them faster and easier to extend. > > Note that the documentation still contains warning language about the > efficiency implications of the "forgiving" adverb. These warnings > need not be heeded -- they are no longer true, and will be removed in > a future release. > >
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