net.sf.saxon.expr
Class ValueComparison

java.lang.Object
  extended bynet.sf.saxon.expr.ComputedExpression
      extended bynet.sf.saxon.expr.BinaryExpression
          extended bynet.sf.saxon.expr.ValueComparison
All Implemented Interfaces:
Expression, Serializable

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
protected  Expression[] operands
           
protected  int 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
 int computeCardinality()
          Determine the static cardinality
 void display(int level, NamePool pool)
          Diagnostic print of expression structure
protected  String displayOperator()
           
 boolean effectiveBooleanValue(XPathContext context)
          Evaluate the expression in a boolean context
 boolean equals(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 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, 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
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
Throws:
XPathException

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

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

computeCardinality

public int computeCardinality()
Determine the static cardinality

Specified by:
computeCardinality in class ComputedExpression

isCommutative

protected static boolean isCommutative(int operator)

equals

public boolean equals(Object other)
Is this expression the same as another expression?


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.


display

public void display(int level,
                    NamePool pool)
Diagnostic print of expression structure

Parameters:
level - indentation level for this expression

displayOperator

protected String displayOperator()