GVM

This project contains my experimental project with extendable syntax grammar.

Brief

Core of project is syntax grammar (gvm.language.Grammar).

General elements of it's:

• gvm.language.TokenID - token identifier, e.g. terminal symbol
• gvm.language.ParseletID - parselet identifier, e.g. non-terminal symbol

Grammar also contains patterns for tokenize from source text to syntax tokens (gvm.language.SyntaxToken).

Example of grammar

This version is used explicit definition of grammar (e.g. parselet definition is imperative)

from gvm.language.combinators import make_sequence
from gvm.language.grammar import Grammar, ParseletKind

grammar = Grammar()

grammar.add_pattern(grammar.add_token('Whitespace'), r'\s+')
grammar.add_pattern(grammar.add_token('Name'), r'[a-zA-Z_][a-zA-Z0-9]*')
number_id = grammar.add_pattern(grammar.add_token('Number'), r'[0-9]+')
expr_id = grammar.add_parselet('expr', kind=ParseletKind.Pratt)
grammar.add_trivia(grammar.tokens['Whitespace'])

implicit = grammar.add_implicit

# expr := Number
grammar.add_parser(expr_id, number_id)
# expr := expr '+' expr
grammar.add_parser(expr_id, make_sequence(expr_id, implicit('+'), expr_id), priority=100)
# expr := expr '-' expr
grammar.add_parser(expr_id, make_sequence(expr_id, implicit('-'), expr_id), priority=100)
# expr := expr '*' expr
grammar.add_parser(expr_id, make_sequence(expr_id, implicit('*'), expr_id), priority=200)
# expr := expr '/' expr
grammar.add_parser(expr_id, make_sequence(expr_id, implicit('/'), expr_id), priority=200)
# expr := '-' expr
grammar.add_parser(expr_id, make_sequence(implicit('-'), expr_id))
# expr := '-' expr
grammar.add_parser(expr_id, make_sequence(implicit('+'), expr_id))
# expr := '(' expr ')'
grammar.add_parser(expr_id, make_sequence(implicit('('), expr_id, implicit(')')))

License

This project is published by MIT license. For full test of license view LICENSE.md

Installation

This project is used Python 3.7 as minimum version.

Also install attrs and pytest (for tests)

Testing

Run pytest