Parsers

LL parsers The LALR(j) parsers are incomparable with LL(k) parsers : for any j and k both greater than 0, there are LALR(j) grammars that are not LL(k) grammars and conversely.

Conflicts As described in the introduction, LL(1) parsers recognize languages that have LL(1) grammars, which are a special case of context-free grammars (CFGs); LL(1) parsers cannot recognize all context-free languages.

Earley parsers apply the techniques and • notation of LR parsers to the task of generating all possible parses for ambiguous grammars such as for human languages.

Knuth proved that LR parsers were the most general-purpose parsers possible that would still be efficient in the worst cases.

LALR parsers handle more grammars than SLR parsers.

LALR parsers have the same states as SLR parsers, but use a more complicated, more precise way of working out the minimum necessary reduction lookaheads for each individual state.

LR parsers differ from other shift-reduce parsers in how they decide when to reduce, and how to pick between rules with similar endings.

Note also that even in validating SGML or XML 1.0 or XML 1.1 parsers, the external entities referenced by an FPI and/or URI in declared notations are not retrieved automatically by the parsers themselves.

Parsers may vary in sophistication; the first text adventure parsers could only handle two-word sentences in the form of verb-noun pairs.

These started as LALR parsers but were later changed to recursive-descent parsers.

Bottom-up parse stack Bottom-Up Parser at step 6 Like other shift-reduce parsers, an LR parser lazily waits until it has scanned and parsed all parts of some construct before committing to what the combined construct is.

But LR parsers are not suited for human languages which need more flexible but slower methods.

Canonical LR parsers handle even more grammars, but use many more states and much larger tables.

Canonical LR parsers use duplicated (or "split") states to better remember the left and right context of a nonterminal's use.

Common Lisp is extensible through standard features such as Lisp macros (code transformations) and reader macros (input parsers for characters).

DCGs are often used to write parsers or list generators, as they also provide a convenient interface to difference lists.

Gilbert and Winnick were frustrated by the genre's text parsers and frequent game over screens.

Grammar for the example A*2 + 1 LR parsers are constructed from a grammar that formally defines the syntax of the input language as a set of patterns.

He showed that the LALR parser has more language recognition power than the LR(0) parser, while requiring the same number of states as the LR(0) parser for a language that can be recognized by both parsers.

However, the "title" attribute of the "img" element specifies the internal entity "example1SVGTitle" whose declaration that does not define an annotation, so it is parsed by validating parsers and the entity replacement text is "Title of example1.