net.sf.saxon.expr

Class IdentityComparison

public final class IdentityComparison extends BinaryExpression

IdentityComparison: a boolean expression that compares two nodes for equals, not-equals, greater-than or less-than based on identity and document ordering
Constructor Summary
IdentityComparison(Expression p1, int op, Expression p2)
Create an identity comparison identifying the two operands and the operator
Method Summary
Expressioncopy()
Copy an expression.
booleaneffectiveBooleanValue(XPathContext context)
ItemevaluateItem(XPathContext context)
Evaluate the expression
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the expression
booleanisGenerateIdEmulation()
Test the flag that indicates different empty-sequence behavior when emulating comparison of two generate-id's
Expressionoptimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
voidsetGenerateIdEmulation(boolean flag)
Set flag to indicate different empty-sequence behavior when emulating comparison of two generate-id's
ExpressiontypeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression

Constructor Detail

IdentityComparison

public IdentityComparison(Expression p1, int op, Expression p2)
Create an identity comparison identifying the two operands and the operator

Parameters: p1 the left-hand operand op the operator, as a token returned by the Tokenizer (e.g. Token.LT) p2 the right-hand operand

Method Detail

copy

public Expression copy()
Copy an expression. This makes a deep copy.

Returns: the copy of the original expression

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)

evaluateItem

public Item evaluateItem(XPathContext context)
Evaluate the expression

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression

Parameters: th the type hierarchy cache

Returns: Type.BOOLEAN

isGenerateIdEmulation

public boolean isGenerateIdEmulation()
Test the flag that indicates different empty-sequence behavior when emulating comparison of two generate-id's

Returns: true if this function is being used to compare generate-id() output

optimize

public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

Parameters: visitor an expression visitor contextItemType the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to ITEM_TYPE

Returns: the original expression, rewritten if appropriate to optimize execution

Throws: XPathException if an error is discovered during this phase (typically a type error)

setGenerateIdEmulation

public void setGenerateIdEmulation(boolean flag)
Set flag to indicate different empty-sequence behavior when emulating comparison of two generate-id's

Parameters: flag true if this function is being used to compare generate-id() output

typeCheck

public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression