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Package nltk_lite :: Package parse :: Module category :: Class Category |
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object
--+ |FeatureStructure
--+ |object
--+ | | |Nonterminal
--+ | Category
GrammarCategory
A Category
is a specialized feature structure, intended
for use in parsing. It can act as a Nonterminal
.
Category
differs from a FeatureStructure
in these ways:
repr()
representation of a Category, the head goes
to the left, on the outside of the brackets. Subclasses of
Category
may change the feature name that is designated
as the head, which is _head by default.
Category
may contain a list of
required features, which are names of features whose value is
None if unspecified. A Category lacking a feature that is required in
it will not unify with any Category that has that feature. If a
required feature's value is None
, it is considered to be
not present. (Mixing different subclasses of Category
is
probably a bad idea.)
True
and False
are allowed as values. A
feature named foo
with a value of True
is
simply expressed as +foo
. Similarly, if it is
False
, it is expressed as -foo
.
Method Summary | |
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__init__(self,
**features)
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__cmp__(self,
other)
| |
Return a new Category based on this one, with its / feature set
to other . | |
bool
|
Return true if self and other assign the same value
to to every feature. |
__hash__(self)
| |
boolean
|
Return true if this non-terminal is not equal to other . |
Return a string representation of this feature structure. | |
__setitem__(self,
name,
value)
| |
Return a deep copy of self . | |
Return a list of all features that have values. | |
Freezing a Category memoizes its hash value, to make comparisons on it faster. | |
bool
|
Returns whether this Category is frozen (immutable). |
get_feature(self,
*args)
| |
has_feature(self,
name)
| |
str or None
|
Return the head of this category (the value shown outside the brackets in its string representation). |
Parse a CFG line involving Categories . (Class method)
| |
list of FeatureStructure
|
Return a list of all feature structures that can be reached from self by multiple feature paths. |
remove_unbound_vars(self)
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Return a list of the names of all required features. | |
Category
|
Return the node value corresponding to this Category . |
Inherited from FeatureStructure :
__getitem__ ,
__str__ ,
apply_bindings ,
equal_values ,
parse ,
rename_variables ,
subsumes ,
unify
Inherited from object :
__delattr__ ,
__getattribute__ ,
__new__ ,
__reduce__ ,
__reduce_ex__ ,
__setattr__
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Class Variable Summary | |
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str |
headname = '_head'
|
str |
k = 'reentrance'
|
list |
requiredFeatures = []
|
SRE_Pattern |
v = \s*->\s*
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Instance Method Details |
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__div__(self, other)
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__eq__(self,
other)
|
__ne__(self, other)
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__repr__(self)
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deepcopy(self, memo=None)
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feature_names(self)
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freeze(self)Freezing a Category memoizes its hash value, to make comparisons on it faster. After freezing, the Category and all its values are immutable.
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frozen(self)Returns whether this Category is frozen (immutable).
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head(self)
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reentrances(self)
|
required_features(self)
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symbol(self)
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Class Method Details |
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parse_rules(cls, s)Parse a
lhs is a Category, and each rhs is a
sequence of Categories.
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Class Variable Details |
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headname
|
k
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requiredFeatures
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v
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Generated by Epydoc 2.1 on Tue Sep 5 09:37:21 2006 | http://epydoc.sf.net |