## net.sf.saxon.expr
Class SingletonComparison

    java.lang.Object
      net.sf.saxon.expr.Expression
          net.sf.saxon.expr.BinaryExpression
              net.sf.saxon.expr.SingletonComparison

All Implemented Interfaces:
  Serializable, SourceLocator, ComparisonExpression, Container, EvaluableItem, SequenceIterable, InstructionInfoProvider

    public class SingletonComparison

extends BinaryExpression
implements ComparisonExpression

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

Fields inherited from class net.sf.saxon.expr.Expression
`EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD`

Constructor Summary
`SingletonComparison(Expression p1, int operator, Expression p2)`

Method Summary
`int` `computeCardinality()` Determine the static cardinality.
`boolean` `convertsUntypedToOther()` Determine whether untyped atomic values should be converted to the type of the other operand
`boolean` `effectiveBooleanValue(XPathContext context)` Evaluate the expression in a boolean context
`Item` `evaluateItem(XPathContext context)` Evaluate the expression in a given context
`AtomicComparer` `getAtomicComparer()` Get the AtomicComparer used to compare atomic values.
`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
`void` `setComparator(AtomicComparer comp)`

Methods inherited from class net.sf.saxon.expr.BinaryExpression
`computeSpecialProperties, display, equals, getOperands, getOperator, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, simplify, typeCheck`

Methods inherited from class net.sf.saxon.expr.Expression

`adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, evaluateAsString, getCardinality, getColumnNumber, getContainingProcedure, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation`

Methods inherited from class java.lang.Object
`getClass, notify, notifyAll, toString, wait, wait, wait`

Methods inherited from interface net.sf.saxon.expr.ComparisonExpression
`getOperands`

Constructor Detail

### SingletonComparison

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

Method Detail

### setComparator

    public void setComparator(AtomicComparer comp)

### getAtomicComparer

    public AtomicComparer getAtomicComparer()

  Description copied from interface: `ComparisonExpression`
  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()

  Description copied from interface: `ComparisonExpression`
  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`

### getItemType

    public ItemType getItemType(TypeHierarchy th)

  Determine the data type of the expression

  Specified by:
    `getItemType` in class `Expression`
  Parameters:
    `th` -
  Returns:
    Type.BOOLEAN

### 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

Copyright (C) Michael H. Kay. All rights reserved.