net.sf.saxon.expr
Class SingletonComparison

java.lang.Object
  |
  +--net.sf.saxon.expr.ComputedExpression
        |
        +--net.sf.saxon.expr.BinaryExpression
              |
              +--net.sf.saxon.expr.SingletonComparison

All Implemented Interfaces:

Expression, java.io.Serializable

public class SingletonComparison

extends net.sf.saxon.expr.BinaryExpression

Class to handle comparisons of singletons. Unlike ValueComparison, this class converts untyped atomic values to the type of the other argument, and returns false (rather than ()) if either operand is ().

See Also:

Serialized Form

Field Summary
protected  Expression[]	operands
protected  int	operator

 

Fields inherited from class net.sf.saxon.expr.ComputedExpression

lineNumber, NO_ARGUMENTS, staticProperties

 

Constructor Summary

SingletonComparison(Expression p1, int operator, Expression p2)

 

Method Summary
Expression	analyze(StaticContext env)           Type-check the expression
int	computeCardinality()           Determine the static cardinality.
void	display(int level, NamePool pool)           Diagnostic print of expression structure
protected  java.lang.String	displayOperator()
boolean	effectiveBooleanValue(XPathContext context)           Evaluate the expression in a boolean context
boolean	equals(java.lang.Object other)           Is this expression the same as another expression?
Item	evaluateItem(XPathContext context)           Evaluate the expression in a given context
ItemType	getItemType()           Determine the data type of the expression
Expression[]	getSubExpressions()           Get the immediate subexpressions of this expression
int	hashCode()           get HashCode for comparing two expressions.
protected static boolean	isCommutative(int operator)
Expression	promote(PromotionOffer offer)           Promote this expression if possible
void	setComparator(java.util.Comparator comp)
void	setDetails(Expression p1, int op, Expression p2)           Identify the two operands and the operator (for use when the default constructor was used)
Expression	simplify()           Simplify an expression

 

Methods inherited from class net.sf.saxon.expr.ComputedExpression

computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, evaluateAsString, getCardinality, getDependencies, getIntrinsicDependencies, getLineNumber, getSourceLocator, getSpecialProperties, iterate, markTailFunctionCalls, setLineNumber, typeError

 

Methods inherited from class java.lang.Object

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

 

Field Detail

operands

protected Expression[] operands

operator

protected int operator

SingletonComparison

public SingletonComparison(Expression p1,
                           int operator,
                           Expression p2)

setComparator

public void setComparator(java.util.Comparator comp)

computeCardinality

public int computeCardinality()

Determine the static cardinality. Returns [1..1]

Overrides:

computeCardinality in class net.sf.saxon.expr.BinaryExpression

analyze

public Expression analyze(StaticContext env)
                   throws XPathException

Type-check the expression

Specified by:

analyze in interface Expression

Overrides:

analyze in class net.sf.saxon.expr.BinaryExpression

Parameters:

env - the static context of the expression

Returns:

the checked expression

XPathException

getItemType

public ItemType getItemType()

Determine the data type of the expression

Returns:

Type.BOOLEAN

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the expression in a given context

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class ComputedExpression

Parameters:

context - the given context for evaluation

Returns:

a BooleanValue representing the result of the numeric comparison of the two operands

Throws:

XPathException - if any dynamic error occurs evaluating the expression

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException

Evaluate the expression in a boolean context

Specified by:

effectiveBooleanValue in interface Expression

Overrides:

effectiveBooleanValue in class ComputedExpression

Parameters:

context - the given context for evaluation

Returns:

a boolean representing the result of the numeric comparison of the two operands

Throws:

XPathException - if any dynamic error occurs evaluating the expression

displayOperator

protected java.lang.String displayOperator()

Overrides:

displayOperator in class net.sf.saxon.expr.BinaryExpression

setDetails

public void setDetails(Expression p1,
                       int op,
                       Expression p2)

Identify the two operands and the operator (for use when the default constructor was used)

Parameters:

p1 - the left-hand operand

op - the operator, as a token returned by the Tokenizer (e.g. Tokenizer.AND)

p2 - the right-hand operand

simplify

public Expression simplify()
                    throws XPathException

Simplify an expression

Specified by:

simplify in interface Expression

Overrides:

simplify in class ComputedExpression

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

promote

public Expression promote(PromotionOffer offer)
                   throws XPathException

Promote this expression if possible

Specified by:

promote in interface Expression

Overrides:

promote in class ComputedExpression

Parameters:

offer - details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression

Returns:

if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression

Throws:

XPathException - if any error is detected

getSubExpressions

public Expression[] getSubExpressions()

Get the immediate subexpressions of this expression

Specified by:

getSubExpressions in interface Expression

Overrides:

getSubExpressions in class ComputedExpression

Returns:

an array containing the sub-expressions of this expression

isCommutative

protected static boolean isCommutative(int operator)

equals

public boolean equals(java.lang.Object other)

Is this expression the same as another expression?

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.

Overrides:

hashCode in class java.lang.Object

display

public void display(int level,
                    NamePool pool)

Diagnostic print of expression structure

Parameters:

level - indentation level for this expression