net.sf.saxon.expr
Class GeneralComparison

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.expr.BinaryExpression
          extended by net.sf.saxon.expr.GeneralComparison
All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, ComparisonExpression, EvaluableItem, SequenceIterable, InstructionInfo, Locator
Direct Known Subclasses:
GeneralComparison20, GeneralComparisonEE

public class GeneralComparison
extends BinaryExpression
implements ComparisonExpression

GeneralComparison: a boolean expression that compares two expressions for equals, not-equals, greater-than or less-than. This implements the operators =, !=, <, >, etc. This implementation is not used when in backwards-compatible mode

See Also:
Serialized Form

Field Summary
protected  AtomicComparer comparer
           
protected  boolean needsRuntimeCheck
           
protected  int singletonOperator
           
 
Fields inherited from class net.sf.saxon.expr.BinaryExpression
operand0, operand1, operator
 
Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, WATCH_METHOD
 
Constructor Summary
GeneralComparison(Expression p0, int op, Expression p1)
          Create a relational expression identifying the two operands and the operator
 
Method Summary
protected static boolean compare(AtomicValue a1, int operator, AtomicValue a2, AtomicComparer comparer, boolean checkTypes, XPathContext context)
          Compare two atomic values
 int computeCardinality()
          Determine the static cardinality.
 boolean convertsUntypedToOther()
          Determine whether untyped atomic values should be converted to the type of the other operand
 Expression copy()
          Copy an expression.
 boolean effectiveBooleanValue(XPathContext context)
          Evaluate the expression in a boolean context
 Item evaluateItem(XPathContext context)
          Evaluate the expression in a given context
protected  void explainExtraAttributes(ExpressionPresenter out)
          Add subclass-specific attributes to the expression tree explanation.
 AtomicComparer getAtomicComparer()
          Get the AtomicComparer used to compare atomic values.
 String getExpressionName()
          Get a name identifying the kind of expression, in terms meaningful to a user.
protected  GeneralComparison getInverseComparison()
           
 ItemType getItemType(TypeHierarchy th)
          Determine the data type of the expression
 int getSingletonOperator()
          Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT, Token.FLE, Token.FGE
 Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)
          Optimize the expression
 void setAtomicComparer(AtomicComparer comparer)
          Set the comparer to be used
 Expression simplify(ExpressionVisitor visitor)
          Simplify an expression
 Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
          Type-check the expression
 
Methods inherited from class net.sf.saxon.expr.BinaryExpression
computeSpecialProperties, displayOperator, equals, explain, getOperands, getOperator, hashCode, isAssociative, isCommutative, isInverse, iterateSubExpressions, promote, replaceSubExpression, setFlattened, toString
 
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setLocationId, staticTypeCheck, suppressValidation, typeError
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface net.sf.saxon.expr.ComparisonExpression
getOperands
 

Field Detail

singletonOperator

protected int singletonOperator

comparer

protected AtomicComparer comparer

needsRuntimeCheck

protected boolean needsRuntimeCheck
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. Token.LT)
p1 - the right-hand operand
Method Detail

setAtomicComparer

public void setAtomicComparer(AtomicComparer comparer)
Set the comparer to be used

Parameters:
comparer - the comparer to be used

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException
Description copied from class: BinaryExpression
Simplify an expression

Overrides:
simplify in class BinaryExpression
Parameters:
visitor - an expression visitor
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

getExpressionName

public String getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user.

Overrides:
getExpressionName in class Expression
Returns:
a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.

getAtomicComparer

public AtomicComparer getAtomicComparer()
Get the AtomicComparer used to compare atomic values. This encapsulates any collation that is used

Specified by:
getAtomicComparer in interface ComparisonExpression

getSingletonOperator

public int getSingletonOperator()
Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT, Token.FLE, Token.FGE

Specified by:
getSingletonOperator in interface ComparisonExpression

convertsUntypedToOther

public boolean convertsUntypedToOther()
Determine whether untyped atomic values should be converted to the type of the other operand

Specified by:
convertsUntypedToOther in interface ComparisonExpression
Returns:
true if untyped values should be converted to the type of the other operand, false if they should be converted to strings.

computeCardinality

public int computeCardinality()
Determine the static cardinality. Returns [1..1]

Overrides:
computeCardinality in class BinaryExpression
Returns:
the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException
Type-check the expression

Overrides:
typeCheck in class BinaryExpression
Parameters:
visitor - an expression visitor
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
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
                    throws XPathException
Optimize the expression

Overrides:
optimize in class BinaryExpression
Parameters:
visitor - an expression visitor
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
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

copy

public Expression copy()
Copy an expression. This makes a deep copy.

Specified by:
copy in class Expression
Returns:
the copy of the original expression

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException
Evaluate the expression in a given context

Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in class Expression
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

Overrides:
effectiveBooleanValue in class Expression
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 checkTypes,
                                 XPathContext context)
                          throws XPathException
Compare two atomic values

Parameters:
a1 - the first value
operator - the operator, for example Token.EQUALS
a2 - the second value
comparer - the comparer to be used to perform the comparison
checkTypes - set to true if the operand types need to be checked for comparability at runtime
context - the XPath evaluation context @return true if the comparison succeeds
Throws:
XPathException

getItemType

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

Specified by:
getItemType in class Expression
Parameters:
th - the type hierarchy cache
Returns:
the value BuiltInAtomicType.BOOLEAN

getInverseComparison

protected GeneralComparison getInverseComparison()

explainExtraAttributes

protected void explainExtraAttributes(ExpressionPresenter out)
Description copied from class: BinaryExpression
Add subclass-specific attributes to the expression tree explanation. Default implementation does nothing; this is provided for subclasses to override.

Overrides:
explainExtraAttributes in class BinaryExpression
Parameters:
out - the output destination for the displayed expression tree


Copyright (c) 2004-2010 Saxonica Limited. All rights reserved.