edu.washington.cs.knowitall.logic

Class LogicExpression<E>

java.lang.Object

edu.washington.cs.knowitall.logic.LogicExpression<E>

Type Parameters:

E - the type of the base expressions

All Implemented Interfaces:

com.google.common.base.Predicate<E>

public class LogicExpression<E>
extends Object
implements com.google.common.base.Predicate<E>

A logic expression engine that operates over user specified objects.

Author:

Michael Schmitz

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	LogicExpression(String input, com.google.common.base.Function<String,Expression.Arg<E>> factory)

Method Summary

Methods

Modifier and Type	Method and Description
boolean	apply(E entity)
Expression.Apply<E>	compile(List<Expression<E>> rpn) Compile a rpn list of tokens into an expression tree.
static <E> LogicExpression<E>	compile(String input, com.google.common.base.Function<String,Expression.Arg<E>> factory)
List<String>	getArgs() Return a list of the arguments contained in the expression.
boolean	isEmpty() If the expression is empty, it returns true for all inputs.
static void	main(String[] args) Iteractively interpret logic statements from stdin such as "true | (true & false)".
List<Expression<E>>	rpn(List<Expression<E>> tokens) Converts an infix logic representation into a postfix logic representation.
List<Expression<E>>	tokenize(String input, com.google.common.base.Function<String,Expression.Arg<E>> factory) Convert an infix string logic representation to an infix list of tokens.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.google.common.base.Predicate

equals

Constructor Detail

LogicExpression

protected LogicExpression(String input,
               com.google.common.base.Function<String,Expression.Arg<E>> factory)
                   throws LogicException.TokenizeLogicException,
                          LogicException.CompileLogicException

Parameters:

input - an infix representation of the logic expression.

factory - a delegate to convert the string representation of an expression to a token.

Throws:

LogicException.TokenizeLogicException

LogicException.CompileLogicException

Method Detail

compile

public static <E> LogicExpression<E> compile(String input,
                             com.google.common.base.Function<String,Expression.Arg<E>> factory)

toString

public String toString()

Overrides:

toString in class Object

isEmpty

public boolean isEmpty()

If the expression is empty, it returns true for all inputs.

Returns:

true iff the expression is empty.

apply

public boolean apply(E entity)

Specified by:

apply in interface com.google.common.base.Predicate<E>

compile

public Expression.Apply<E> compile(List<Expression<E>> rpn)

Compile a rpn list of tokens into an expression tree.

Parameters:

rpn - a list of tokens in infix form.

Returns:

an expression tree.

getArgs

public List<String> getArgs()

Return a list of the arguments contained in the expression.

Returns:

tokenize

public List<Expression<E>> tokenize(String input,
                           com.google.common.base.Function<String,Expression.Arg<E>> factory)
                             throws LogicException.TokenizeLogicException

Convert an infix string logic representation to an infix list of tokens.

Parameters:

input - an infix string logic representation.

factory - a delegate that converts a string representation of an argument into a token object. @return

Throws:

LogicException.TokenizeLogicException

rpn

public List<Expression<E>> rpn(List<Expression<E>> tokens)
                        throws LogicException.CompileLogicException

Converts an infix logic representation into a postfix logic representation.

Parameters:

tokens - a list of tokens in infix form.

Returns:

a list of tokens in postfix (rpn) form.

Throws:

LogicException.CompileLogicException

main

public static void main(String[] args)

Iteractively interpret logic statements from stdin such as "true | (true & false)".

Parameters:

args -