Package nltk :: Package sem :: Module logic

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Module logic

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A version of first order predicate logic, built on top of the typed lambda calculus.

Classes

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Tokens

Variable

Type

ComplexType

BasicType

EntityType

TruthValueType

EventType

AnyType

TypeException

InconsistentTypeHierarchyException

TypeResolutionException

IllegalTypeException

SubstituteBindingsI
An interface for classes that can perform substitutions for variables.

Expression
This is the base abstract object for all logical expressions

ApplicationExpression
This class is used to represent two related types of logical expressions.

AbstractVariableExpression
This class represents a variable to be used as a predicate or entity

IndividualVariableExpression
This class represents variables that take the form of a single lowercase character (other than 'e') followed by zero or more digits.

FunctionVariableExpression
This class represents variables that take the form of a single uppercase character followed by zero or more digits.

EventVariableExpression
This class represents variables that take the form of a single lowercase 'e' character followed by zero or more digits.

ConstantExpression
This class represents variables that do not take the form of a single character followed by zero or more digits.

VariableBinderExpression
This an abstract class for any Expression that binds a variable in an Expression.

LambdaExpression

QuantifiedExpression

ExistsExpression

AllExpression

NegatedExpression

BinaryExpression

BooleanExpression

AndExpression
This class represents conjunctions

OrExpression
This class represents disjunctions

ImpExpression
This class represents implications

IffExpression
This class represents biconditionals

EqualityExpression
This class represents equality expressions like "(x = y)".

LogicParser
A lambda calculus expression parser.

StringTrie

ParseException

UnexpectedTokenException

ExpectedMoreTokensException

Functions

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boolean_ops()
Boolean operators

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equality_preds()
Equality predicates

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binding_ops()
Binding operators

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unique_variable(pattern=None, ignore=None)
Return a new, unique variable.

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skolem_function(univ_scope=None)
Return a skolem function over the variables in univ_scope param univ_scope

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parse_type(type_string)

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typecheck(expressions, signature=None)
Ensure correct typing across a collection of Expressions. source code

VariableExpression(variable)
This is a factory method that instantiates and returns a subtype of AbstractVariableExpression appropriate for the given variable. source code

is_indvar(expr)
An individual variable must be a single lowercase character other than 'e', followed by zero or more digits.

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is_funcvar(expr)
A function variable must be a single uppercase character followed by zero or more digits.

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is_eventvar(expr)
An event variable must be a single lowercase 'e' character followed by zero or more digits.

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demo()

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demo_errors()

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demoException(s)

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printtype(ex)

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Variables

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APP = 'APP'

_counter = Counter()

TRUTH_TYPE = t

ENTITY_TYPE = e

EVENT_TYPE = v

ANY_TYPE = ?

Function Details

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unique_variable(pattern=None, ignore=None)

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Return a new, unique variable. param pattern: Variable that is being replaced. The new variable must be the same type. param term: a set of Variables that should not be returned from this function. return: Variable

typecheck(expressions, signature=None)

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Ensure correct typing across a collection of Expressions.

Parameters:

expressions - a collection of expressions
signature - dict that maps variable names to types (or string representations of types)

is_indvar(expr)

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An individual variable must be a single lowercase character other than 'e', followed by zero or more digits.

Parameters:

expr - str

Returns:

boolean True if expr is of the correct form

is_funcvar(expr)

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A function variable must be a single uppercase character followed by zero or more digits.

Parameters:

expr - str

Returns:

boolean True if expr is of the correct form

is_eventvar(expr)

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An event variable must be a single lowercase 'e' character followed by zero or more digits.

Parameters:

expr - str

Returns:

boolean True if expr is of the correct form