Package nltk_lite :: Module featurestructure :: Class AliasedFeatureVariable

Class AliasedFeatureVariable

SubstituteBindingsI --+    
                      |    
        FeatureVariable --+
                          |
                         AliasedFeatureVariable

A set of variables that are constrained to be equal. An aliased variable can be used in place of a simple variable. In particular, an aliased variable stands for a single feature value, and requires that each its aliases are bound to that same value. Aliased variables can be categorized according to their values in a set of bindings:

An aliased variable is unbound if none of its aliases is assigned a value.
An aliased variable is bound if at least one of its aliases is bound, and all of its bound aliases are assigned the same value. (If at least one alias is unbound, then the aliased variable is said to be partially bound.)
An aliased variable is inconsistant if two or more aliases are bound to different values.

Instance Methods

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__init__(self, *aliases)
Construct a new feature structure variable that contains the given aliases.

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string

identifier(self)
Raise ValueError, since aliased variables do not have a single identifier. source code

aliases(self)
Returns: A list of the variables that are constrained to be equal by this aliased variable.

source code

__repr__(self)
Returns: A string representation of this feature structure variable.

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__cmp__(self)

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__hash__(self)

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Inherited from FeatureVariable: alias, substitute_bindings

Static Methods

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Inherited from FeatureVariable: parse

Class Variables

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Inherited from FeatureVariable (private): _next_numbered_id

Instance Variables

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_aliases
The set of aliases contained by this aliased variable.

Method Details

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init(self, aliases)
(Constructor)*

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Construct a new feature structure variable that contains the given aliases. If aliases contains aliased variables, then they are replaced by their lists of aliases.

Raises:

ValueError - If no aliases are specified.

Overrides: FeatureVariable.__init__

identifier(self)

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Raise ValueError, since aliased variables do not have a single identifier.

Returns: string: This variable's unique identifier.
Overrides: FeatureVariable.identifier

aliases(self)

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Returns:: A list of the variables that are constrained to be equal by this aliased variable.

repr(self)
(Representation operator)

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Returns:: A string representation of this feature structure variable. A feature structure variable with identifiers X1, X2, ..., Xn is represented as '?<X1=X2=...=Xn>'.
Overrides: FeatureVariable.__repr__