CYK ParserĪ CYK parser can parse any context-free grammar at O(n^3*|G|). This is an improvement to LALR(1) that is unique to Lark. It’s surprisingly effective at resolving common terminal collisions, and allows to parse languages that LALR(1) was previously incapable of parsing. So at each point, the lexer only matches the subgroup of terminals that are legal at that parser state, instead of all of the terminals. The contextual lexer communicates with the parser, and uses the parser's lookahead prediction to narrow its choice of tokens. Lark extends the traditional YACC-based architecture with a contextual lexer, which automatically provides feedback from the parser to the lexer, making the LALR(1) algorithm stronger than ever. Lark comes with an efficient implementation that outperforms every other parsing library for Python (including PLY) It can parse most programming languages (For example: Python and Java). It's incredibly fast and requires very little memory. LALR(1) is a very efficient, true-and-tested parsing algorithm. Lark also supports user-defined rule priority to steer the automatic ambiguity resolution. The user may request to recieve all derivations (using ambiguity='explicit'), or let Lark automatically choose the most fitting derivation (default behavior). Lark by default can handle any ambiguity in the grammar (Earley+dynamic). So choose this only if you know why! Activate with lexer='standard' Doing so will provide a speed benefit, but will tokenize without using Earley's ambiguity-resolution ability. It's possible to bypass the dynamic lexer, and use the regular Earley parser with a traditional lexer, that tokenizes as an independant first step. This feature is used by default, but can also be requested explicitely using lexer='dynamic'. This is a huge improvement to Earley that is unique to Lark. Lark's Earley implementation runs on top of a skipping chart parser, which allows it to use regular expressions, instead of matching characters one-by-one. Most programming languages are LR, and can be parsed at a linear time. Lark implements the following parsing algorithms: EarleyĪn Earley Parser is a chart parser capable of parsing any context-free grammar at O(n^3), and O(n^2) when the grammar is unambiguous. Standard library of terminals (strings, numbers, names, etc.).Automatic terminal collision resolution.Stand-alone parser generator - create a small independent parser to embed in your project.Builds a parse-tree (AST) automagically based on the grammar.EBNF-inspired grammar, with extra features (See: Grammar Reference).
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