net.sf.saxon.expr
Class ValueComparison

java.lang.Object
  net.sf.saxon.expr.ComputedExpression
      net.sf.saxon.expr.BinaryExpression
          net.sf.saxon.expr.ValueComparison

All Implemented Interfaces:

Serializable, Expression

public final class ValueComparison
extends BinaryExpression

ValueComparison: a boolean expression that compares two atomic values for equals, not-equals, greater-than or less-than. Implements the operators eq, ne, lt, le, gt, ge

See Also:

Serialized Form

Field Summary

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

operands, operator

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

lineNumber, NO_ARGUMENTS, staticProperties

Constructor Summary

ValueComparison(Expression p1, int op, Expression p2)
Create a relational expression identifying the two operands and the operator

Method Summary

Expression	analyze(StaticContext env) Type-check the expression
protected static boolean	compare(AtomicValue v1, int op, AtomicValue v2, AtomicComparer collator) Compare two atomic values, using a specified operator and collation
boolean	effectiveBooleanValue(XPathContext context) Evaluate the expression in a boolean context
Item	evaluateItem(XPathContext context) Evaluate the expression in a given context
ItemType	getItemType() Determine the data type of the expression

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

computeCardinality, display, displayOperator, equals, getSubExpressions, hashCode, isCommutative, promote, setDetails, simplify

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

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

Methods inherited from class java.lang.Object

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

Constructor Detail

ValueComparison

public ValueComparison(Expression p1,
                       int op,
                       Expression p2)

Create a relational expression 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. Tokenizer.LT)

p2 - the right-hand operand

Method Detail

analyze

public Expression analyze(StaticContext env)
                   throws XPathException

Type-check the expression

Specified by:

analyze in interface Expression

Overrides:

analyze in class BinaryExpression

Parameters:

env - the static context of the expression

Returns:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

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

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

compare

protected static boolean compare(AtomicValue v1,
                                 int op,
                                 AtomicValue v2,
                                 AtomicComparer collator)
                          throws XPathException.Type

Compare two atomic values, using a specified operator and collation

Throws:

XPathException.Type - if the values are not comparable

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

getItemType

public ItemType getItemType()

Determine the data type of the expression

Returns:

Type.BOOLEAN