./devel/py-grako, Grammar compiler

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Branch: pkgsrc-2021Q4, Version: 3.99.9, Package name: py39-grako-3.99.9, Maintainer: pkgsrc-users

Grako (for grammar compiler) is a tool that takes grammars in a variation of
EBNF as input, and outputs memoizing (Packrat) PEG parsers in Python.

Grako can also compile a grammar stored in a string into a Grammar object that
can be used to parse any given input, much like the re module does with
regular expressions.

Grako is different from other PEG parser generators:
* Generated parsers use Python's very efficient exception-handling system to
backtrack. Grako generated parsers simply assert what must be parsed. There
are no complicated if-then-else sequences for decision making or
backtracking. Memoization allows going over the same input sequence several
times in linear time.
* Positive and negative lookaheads, and the cut element (with its cleaning of
the memoization cache) allow for additional, hand-crafted optimizations at
the grammar level.
* Delegation to Python's re module for lexemes allows for (Perl-like) powerful
and efficient lexical analysis.
* The use of Python's context managers considerably reduces the size of the
generated parsers for code clarity, and enhanced CPU-cache hits.
* Include files, rule inheritance, and rule inclusion give Grako grammars
considerable expressive power.
* Automatic generation of Abstract Syntax Trees and Object Models, along with
Model Walkers and Code Generators make analysis and translation approachable.

Master sites:

Filesize: 155.545 KB

Version history: (Expand)