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:
Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator

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 operand0
           
protected  Expression operand1
           
protected  int operator
           
 
Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
 
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
SingletonComparison(Expression p1, int operator, Expression p2)
           
 
Method Summary
 Expression analyze(StaticContext env, ItemType contextItemType)
          Type-check the expression
 int computeCardinality()
          Determine the static cardinality.
 void display(int level, NamePool pool, java.io.PrintStream out)
          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
 int hashCode()
          get HashCode for comparing two expressions.
protected static boolean isCommutative(int operator)
           
 java.util.Iterator iterateSubExpressions()
          Get the immediate subexpressions of this expression
 Expression promote(PromotionOffer offer)
          Promote this expression if possible
 void setComparator(java.util.Comparator comp)
           
 Expression simplify(StaticContext env)
          Simplify an expression
 
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, dynamicError, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, typeError
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

operand0

protected Expression operand0

operand1

protected Expression operand1

operator

protected int operator
Constructor Detail

SingletonComparison

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

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,
                          ItemType contextItemType)
                   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
contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
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

simplify

public Expression simplify(StaticContext env)
                    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

iterateSubExpressions

public java.util.Iterator iterateSubExpressions()
Get the immediate subexpressions of this expression

Specified by:
iterateSubExpressions in interface Expression
Overrides:
iterateSubExpressions in class ComputedExpression
Returns:
an iterator 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,
                    java.io.PrintStream out)
Diagnostic print of expression structure

Parameters:
level - indentation level for this expression
pool - NamePool used to expand any names appearing in the expression
out - Output destination