nltk.grammar.FeatureGrammar

type FeatureGrammar

object --+ | ContextFreeGrammar --+ | FeatureGrammar

A feature-based grammar. This is equivalent to a ContextFreeGrammar whose nonterminals are FeatStructNonterminals.

A grammar consists of a start state and a set of productions. The set of terminals and nonterminals is implicitly specified by the productions.

Instance Methods

[hide private]

__init__(self, start, productions)
Create a new feature-based grammar, from the given start state and set of Productions. source code

_calculate_indexes(self)

source code

list of Production

productions(self, lhs=None, rhs=None, empty=False)
Return the grammar productions, filtered by the left-hand side or the first item in the right-hand side.

source code

set of Nonterminal

leftcorners(self, cat)
Return the set of all words that the given category can start with.

source code

set of Nonterminal

leftcorner_parents(self, cat)
Return the set of all categories for which the given category is a left corner.

source code

_get_type_if_possible(self, item)
Helper function which returns the TYPE feature of the item, if it exists, otherwise it returns the item itself source code

Inherited from ContextFreeGrammar: __repr__, __str__, check_coverage, is_binarised, is_chomsky_normal_form, is_flexible_chomsky_normal_form, is_leftcorner, is_lexical, is_nonempty, is_nonlexical, max_len, min_len, start

Inherited from ContextFreeGrammar (private): _calculate_grammar_forms, _calculate_leftcorners

init(self, start, productions)
(Constructor)

source code

Create a new feature-based grammar, from the given start state and set of Productions.

Parameters:

start (FeatStructNonterminal) - The start symbol
productions (list of Production) - The list of productions that defines the grammar

Overrides: ContextFreeGrammar.__init__

productions(self, lhs=None, rhs=None, empty=False)

source code

Return the grammar productions, filtered by the left-hand side or the first item in the right-hand side.

Parameters:

lhs - Only return productions with the given left-hand side.
rhs - Only return productions with the given first item in the right-hand side.
empty - Only return productions with an empty right-hand side.

Returns: list of Production

A list of productions matching the given constraints.

Overrides: ContextFreeGrammar.productions