Package nltk :: Package sem :: Module evaluate

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Module evaluate

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This module provides data structures for representing first-order models.

Classes

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Error

Undefined

Valuation
A dictionary which represents a model-theoretic Valuation of non-logical constants.

Assignment
A dictionary which represents an assignment of values to variables.

Model
A first order model is a domain D of discourse and a valuation V.

Functions

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trace(f, *args, **kw)

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bool

is_rel(s)
Check whether a set represents a relation (of any arity).

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set of tuple of str

set2rel(s)
Convert a set containing individuals (strings or numbers) into a set of unary tuples.

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int of tuple of str

arity(rel)
Check the arity of a relation.

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bool or a set of tuples

app(rel, arg, trace=False)
Apply a relation (as set of tuples) to an argument.

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VariableExpression or IndividualVariableExpression

make_VariableExpression(var)
Convert a string into an instance of VariableExpression

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propdemo(trace=None)
Example of a propositional model.

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folmodel(trace=None)
Example of a first-order model.

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foldemo(trace=None)
Interpretation of closed expressions in a first-order model.

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satdemo(trace=None)
Satisfiers of an open formula in a first order model.

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demo(num=0, trace=None)
Run exists demos.

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Variables

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mult = 30

Function Details

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is_rel(s)

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Check whether a set represents a relation (of any arity).

Parameters:

s (set) - a set containing tuples of str elements

Returns: bool

set2rel(s)

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Convert a set containing individuals (strings or numbers) into a set of unary tuples. Any tuples of strings already in the set are passed through unchanged.

For example:

set(['a', 'b']) => set([('a',), ('b',)])
set([3, 27]) => set([('3',), ('27',)])

Parameters:

s (set)

Returns: set of tuple of str

arity(rel)

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Check the arity of a relation.

Parameters:

rel (set of tuples)

Returns: int of tuple of str

app(rel, arg, trace=False)

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Apply a relation (as set of tuples) to an argument.

If rel has arity n <= 1, then app returns a Boolean value. If If rel has arity n > 1, then app returns a relation of arity n-1.

Parameters:

arg - any appropriate semantic argument
rel (set of tuples)

Returns: bool or a set of tuples

Decorators:

@decorator(trace)

make_VariableExpression(var)

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Convert a string into an instance of VariableExpression

Parameters:

var (str)

Returns: VariableExpression or IndividualVariableExpression

demo(num=0, trace=None)

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Run exists demos.

num = 1: propositional logic demo
num = 2: first order model demo (only if trace is set)
num = 3: first order sentences demo
num = 4: satisfaction of open formulas demo
any other value: run all the demos

Parameters:

trace - trace = 1, or trace = 2 for more verbose tracing