Module org.apache.jena.arq

Package org.apache.jena.sparql.expr

Class ExprNone

java.lang.Object

org.apache.jena.sparql.expr.ExprNode

org.apache.jena.sparql.expr.ExprNone

All Implemented Interfaces:

Expr

public class ExprNone
extends ExprNode

Marker, used in place of a null. This may be tested for using ==

Field Summary

Fields inherited from interface org.apache.jena.sparql.expr.Expr

CMP_EQUAL, CMP_GREATER, CMP_INDETERMINATE, CMP_LESS, CMP_UNEQUAL, NONE

Method Summary

Modifier and Type	Method	Description
Expr	applyNodeTransform(NodeTransform transform)	Rewrite, applying a node->node transformation
Expr	copySubstitute(Binding binding)	Deep copy with substitution
boolean	equals(Expr other, boolean bySyntax)	General equality operation - consider this to be 'protected'
NodeValue	eval(Binding binding, FunctionEnv env)	Evaluate this expression against the binding
int	hashCode()	Expr are used in both syntax and algebra.
void	visit(ExprVisitor visitor)

Methods inherited from class org.apache.jena.sparql.expr.ExprNode

asVar, deepCopy, equals, equalsBySyntax, getConstant, getExpr, getExprVar, getFunction, getGraphPattern, getVarName, getVarsMentioned, isConstant, isExpr, isFunction, isGraphPattern, isSatisfied, isVariable, toString

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Method Details

visit

public void visit(ExprVisitor visitor)

eval

public NodeValue eval(Binding binding,
 FunctionEnv env)

Description copied from interface: Expr

Evaluate this expression against the binding

Specified by:

eval in interface Expr

Specified by:

eval in class ExprNode

hashCode

public int hashCode()

Description copied from interface: Expr

Expr are used in both syntax and algebra. There is no syntax to algebra translation step because the parser uses operator precedence to build the right evaluation structure directly.

The exceptions to this are the NOT EXISTS and EXISTS expressions which involve a query pattern. As a result there are different ways in syntax to produce the same algebra form.

Two Expr are considered equal if they are equal as algebra expressions. hashCode and equals must implement that.

There is also equalsBySyntax. Because two different syntax forms can yield the same algebra, but two different algebra forms must be different syntax, equalsBySyntax implies equals (by algebra).

Hence, different hashCode => not equalsBySyntax.

Specified by:

hashCode in interface Expr

Specified by:

hashCode in class ExprNode

equals

public boolean equals(Expr other,
 boolean bySyntax)

Description copied from interface: Expr

General equality operation - consider this to be 'protected'

Specified by:

equals in interface Expr

Specified by:

equals in class ExprNode

copySubstitute

public Expr copySubstitute(Binding binding)

Description copied from interface: Expr

Deep copy with substitution

Specified by:

copySubstitute in interface Expr

Specified by:

copySubstitute in class ExprNode

applyNodeTransform

public Expr applyNodeTransform(NodeTransform transform)

Description copied from interface: Expr

Rewrite, applying a node->node transformation

Specified by:

applyNodeTransform in interface Expr

Specified by:

applyNodeTransform in class ExprNode