net.sf.saxon.expr
Class ValueComparison

java.lang.Object
  extended by net.sf.saxon.expr.ComputedExpression
      extended by net.sf.saxon.expr.BinaryExpression
          extended by 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