nxt.util

Class BooleanExpression

java.lang.Object

nxt.util.BooleanExpression

public class BooleanExpression
extends java.lang.Object

A boolean expression in disjunctive normal form - i.e. a disjunction of one or more conjunctions of one or more literals

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	BooleanExpression.BadSyntaxException
static class	BooleanExpression.BooleanExpressionException
static class	BooleanExpression.SemanticWarning
static class	BooleanExpression.SemanticWarningType
static class	BooleanExpression.SyntaxError
static class	BooleanExpression.Value

Field Summary

Fields

Modifier and Type	Field and Description
static char	CONJUNCTION_OPERATOR
static char	DISJUNCTION_OPERATOR
static char	NEGATION_OPERATOR

Constructor Summary

Constructors

Constructor and Description
BooleanExpression(java.lang.String expression)

Method Summary

Modifier and Type	Method and Description
BooleanExpression.Value	evaluate(java.util.Map<java.lang.String,BooleanExpression.Value> variableValues) Evaluates the expression with the provided variable values.
static boolean	fastImplicationCheck(BooleanExpression antecedent, BooleanExpression consequent) Performs fast check whether "antecedent -> consequent" evaluates to TRUE.
int	getLiteralsCount()
java.util.List<BooleanExpression.SemanticWarning>	getSemanticWarnings()
BooleanExpression.BadSyntaxException	getSyntaxException()
java.util.Set<java.lang.String>	getVariables() Returns the set of variables used is this expression
boolean	hasErrors(boolean treatWarningsAsErrors)

Methods inherited from class java.lang.Object

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

Field Detail

CONJUNCTION_OPERATOR

public static final char CONJUNCTION_OPERATOR

See Also:

Constant Field Values

DISJUNCTION_OPERATOR

public static final char DISJUNCTION_OPERATOR

See Also:

Constant Field Values

NEGATION_OPERATOR

public static final char NEGATION_OPERATOR

See Also:

Constant Field Values

Constructor Detail

BooleanExpression

public BooleanExpression(java.lang.String expression)

Parameters:

expression - The expression string in disjunctive normal form

Method Detail

evaluate

public BooleanExpression.Value evaluate(java.util.Map<java.lang.String,BooleanExpression.Value> variableValues)
                                 throws BooleanExpression.BadSyntaxException

Evaluates the expression with the provided variable values. If for some of the expression variables (see getVariables()), there is no value in the variableValues map (or the value is null), the value is considered BooleanExpression.Value.UNKNOWN. In that case, the result may also be BooleanExpression.Value.UNKNOWN - meaning that currently we cannot evaluate the expression to neither BooleanExpression.Value.TRUE or BooleanExpression.Value.FALSE. But it is not necessary BooleanExpression.Value.UNKNOWN - the available values may still be enough to return a definitive result

Parameters:

variableValues - The keys are variable names, the values are the respective boolean BooleanExpression.Values

Returns:

The result from evaluating the expression

Throws:

BooleanExpression.BadSyntaxException - in case of error in the expression syntax

fastImplicationCheck

public static boolean fastImplicationCheck(BooleanExpression antecedent,
                                           BooleanExpression consequent)
                                    throws BooleanExpression.BadSyntaxException

Performs fast check whether "antecedent -> consequent" evaluates to TRUE. The implication "antecedent -> consequent" evaluates to TRUE when the antecedent is more restrictive than the consequent, i.e. when in no case the antecedent will be TRUE if the consequent is FALSE. In other words, if consequent is FALSE, then antecedent must also be FALSE. The current implementation only uses the boolean algebra laws and does not create the full truth table of the expression. So if this method returns true, this means that "antecedent -> consequent" evaluates to TRUE, but if the method returns false, it is still possible that "antecedent -> consequent" evaluates to TRUE - e.g. if the antecedent is always equal to FALSE, or the consequent is always equal to TRUE

Parameters:

antecedent - The antecedent of the conditional

consequent - The consequent of the conditional

Returns:

true if the boolean expression "antecedent -> consequent" evaluates to TRUE

Throws:

BooleanExpression.BadSyntaxException - in case of error in the expressions syntax

getVariables

public java.util.Set<java.lang.String> getVariables()

Returns the set of variables used is this expression

Returns:

the set of variables used is this expression

getLiteralsCount

public int getLiteralsCount()

hasErrors

public boolean hasErrors(boolean treatWarningsAsErrors)

getSyntaxException

public BooleanExpression.BadSyntaxException getSyntaxException()

getSemanticWarnings

public java.util.List<BooleanExpression.SemanticWarning> getSemanticWarnings()