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In formal language theory, the left corner of a production rule in a context-free grammar is the left-most symbol on the right side of the rule. [1] For example, in the rule A→Xα, X is the left corner. The left corner table associates to a symbol all possible left corners for that symbol, and the left corners of those symbols, etc. Given the ...
The multiple valid parse trees are computed simultaneously, without backtracking. GLR is sometimes helpful for computer languages that are not easily described by a conflict-free LALR(1) grammar. LC Left corner parsers use LR bottom-up techniques for recognizing the left end of alternative grammar rules. When the alternatives have been narrowed ...
In computer science, a left corner parser is a type of chart parser used for parsing context-free grammars.It combines the top-down and bottom-up approaches of parsing. The name derives from the use of the left corner of the grammar's production rules.
Grammatical abbreviations are generally written in full or small caps to visually distinguish them from the translations of lexical words. For instance, capital or small-cap PAST (frequently abbreviated to PST) glosses a grammatical past-tense morpheme, while lower-case 'past' would be a literal translation of a word with that meaning.
The following example demonstrates the common case of parsing a computer language with two levels of grammar: lexical and syntactic. The first stage is the token generation, or lexical analysis, by which the input character stream is split into meaningful symbols defined by a grammar of regular expressions.
A grammar that uses phrase structure rules is a type of phrase structure grammar. Phrase structure rules as they are commonly employed operate according to the constituency relation, and a grammar that employs phrase structure rules is therefore a constituency grammar ; as such, it stands in contrast to dependency grammars , which are based on ...
A GLR parser (generalized left-to-right rightmost derivation parser) is an extension of an LR parser algorithm to handle non-deterministic and ambiguous grammars. [1] The theoretical foundation was provided in a 1974 paper [ 2 ] by Bernard Lang (along with other general context-free parsers such as GLL).
The nature of branching is most visible with full trees. The following trees have been chosen to illustrate the extent to which a structure can be entirely left- or entirely right-branching. The following sentence is completely left-branching. The constituency-based trees are on the left, and the dependency-based trees are on the right: [7]