net.sf.saxon.expr
Class GeneralComparison

java.lang.Object
  extended by net.sf.saxon.expr.ComputedExpression
      extended by net.sf.saxon.expr.BinaryExpression
          extended by net.sf.saxon.expr.GeneralComparison
All Implemented Interfaces:
Serializable, Expression

public class GeneralComparison
extends BinaryExpression

GeneralComparison: a boolean expression that compares two expressions for equals, not-equals, greater-than or less-than. This implements the operators =, !=, <, >, etc.

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
GeneralComparison(Expression p0, int op, Expression p1)
          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 a1, int operator, AtomicValue a2, AtomicComparer comparer, boolean backwardsCompatible)
          Compare two atomic values
protected  String displayOperator()
           
 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
 void setDetails(Expression p0, int op, Expression p1)
          Identify the two operands and the operator (for use when the default constructor was used)
 
Methods inherited from class net.sf.saxon.expr.BinaryExpression
computeCardinality, display, equals, getSubExpressions, hashCode, isCommutative, promote, 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

GeneralComparison

public GeneralComparison(Expression p0,
                         int op,
                         Expression p1)
Create a relational expression identifying the two operands and the operator

Parameters:
p0 - the left-hand operand
op - the operator, as a token returned by the Tokenizer (e.g. Tokenizer.LT)
p1 - the right-hand operand
Method Detail

setDetails

public void setDetails(Expression p0,
                       int op,
                       Expression p1)
Description copied from class: BinaryExpression
Identify the two operands and the operator (for use when the default constructor was used)

Overrides:
setDetails in class BinaryExpression
Parameters:
p0 - the left-hand operand
op - the operator, as a token returned by the Tokenizer (e.g. Tokenizer.AND)
p1 - the right-hand operand

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

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

compare

protected static boolean compare(AtomicValue a1,
                                 int operator,
                                 AtomicValue a2,
                                 AtomicComparer comparer,
                                 boolean backwardsCompatible)
                          throws XPathException
Compare two atomic values

Throws:
XPathException

getItemType

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

Returns:
Type.BOOLEAN

displayOperator

protected String displayOperator()
Overrides:
displayOperator in class BinaryExpression