Package nltk_lite :: Package semantics :: Module evaluate :: Class Assignment

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Class Assignment

object --+    
         |    
      dict --+
             |
            Assignment

A dictionary which represents an assignment of values to variables.

An assigment can only assign values from its domain.

If an unknown expression a is passed to a model M's interpretation function i, i will first check whether M's valuation assigns an interpretation to a as a constant, and if this fails, i will delegate the interpretation of a to g. g only assigns values to individual variables (i.e., members of the class IndVariableExpression in the logic module. If a variable is not assigned a value by g, it will raise an Undefined exception.

Instance Methods

__init__(self, domain, assignment=None)
x.__init__(...) initializes x; see x.__class__.__doc__ for signature

source code

__getitem__(self, key)
x[y]

source code

copy(self)
Returns: a shallow copy of D

source code

purge(self, var=None)
Remove one or all keys (i.e.

source code

__str__(self)
Pretty printing for assignments.

source code

_addvariant(self)
Create a more pretty-printable version of the assignment.

source code

add(self, val, var)
Add a new variable-value pair to the assignment, and update self.variant. source code

Inherited from dict: __cmp__, __contains__, __delitem__, __eq__, __ge__, __getattribute__, __gt__, __hash__, __iter__, __le__, __len__, __lt__, __ne__, __new__, __repr__, __setitem__, clear, fromkeys, get, has_key, items, iteritems, iterkeys, itervalues, keys, pop, popitem, setdefault, update, values

Inherited from object: __delattr__, __reduce__, __reduce_ex__, __setattr__

Properties

Inherited from object: __class__

Method Details

init(self, domain, assignment=None)
(Constructor)

x.__init__(...) initializes x; see x.__class__.__doc__ for signature

Returns:

new empty dictionary

Overrides: dict.__init__

(inherited documentation)

getitem(self, key)
(Indexing operator)

x[y]

Overrides: dict.__getitem__: (inherited documentation)

copy(self)

Returns:

a shallow copy of D

Overrides: dict.copy

(inherited documentation)

purge(self, var=None)

Remove one or all keys (i.e. logic variables) from an assignment, and update self.variant.

Parameters:

var - a Variable acting as a key for the assignment.

str(self)
(Informal representation operator)

Pretty printing for assignments. {'x', 'u'} appears as 'g[u/x]'

Overrides: object.__str__

add(self, val, var)

Add a new variable-value pair to the assignment, and update self.variant.

We write the arguments in the order 'val, var' by analogy with the notation 'g[u/x]'.