IsLastExpression

java.lang.Object
- net.sf.saxon.expr.Expression
- - net.sf.saxon.expr.IsLastExpression

All Implemented Interfaces:

IdentityComparable
```
public final class IsLastExpression
extends Expression
```
A position() eq last() expression, generated by the optimizer.

Field Summary
- Fields inherited from class net.sf.saxon.expr.Expression
  EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors
Constructor and Description
`IsLastExpression(boolean condition)` Construct a condition that tests position() eq last() (if condition is true) or position() ne last() (if condition is false).

Method Summary

Methods
Modifier and Type	Method and Description
`int`	`computeCardinality()` Determine the static cardinality
`int`	`computeSpecialProperties()` Determine the special properties of this expression
`Expression`	`copy()` Copy an expression.
`boolean`	`equals(Object other)` Is this expression the same as another expression?
`BooleanValue`	`evaluateItem(XPathContext c)` Evaluate an expression as a single item.
`void`	`export(ExpressionPresenter destination)` Diagnostic print of expression structure.
`boolean`	`getCondition()` Get the condition we are testing for
`ExpressionCompiler`	`getExpressionCompiler()` Return the compiler for the IsLast expression
`int`	`getImplementationMethod()` An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
`int`	`getIntrinsicDependencies()` Get the dependencies of this expression on the context
`ItemType`	`getItemType()` Determine the data type of the expression
`protected StreamingAdjunct`	`getStreamingAdjunct()` Get a class that supports streamed evaluation of this expression
`int`	`hashCode()` Hashcode supporting equals()
`Expression`	`optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType)` Perform optimisation of an expression and its subexpressions.
`String`	`toString()` The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.
`Expression`	`typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)` Perform type checking of an expression and its subexpressions.

Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExpressionName, getHostLanguage, getIntegerBounds, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getPosture, getPostureAndSweepIfKnown, getProperties, getProperty, getRetainedStaticContext, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStreamability, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, operands, operandSparseList, optimizeChildren, optimizeForType, process, promote, promoteChildren, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setFiltered, setFlattened, setLocation, setParentExpression, setPostureAndSweep, setRetainedStaticContext, setRetainedStaticContextLocally, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toShortString, toStreamingPattern, typeCheckChildren, typeError, unordered

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - IsLastExpression
```
public IsLastExpression(boolean condition)
```
    Construct a condition that tests position() eq last() (if condition is true) or position() ne last() (if condition is false).
    
    Parameters:
    condition - true if we are testing "equals", false for "not equals".
- Method Detail
  - getCondition
```
public boolean getCondition()
```
    Get the condition we are testing for
    
    Returns:
    true if we are testing "equals", false for "not equals".
  - typeCheck
```
public Expression typeCheck(ExpressionVisitor visitor,
                   ContextItemStaticInfo contextInfo)
```
    Description copied from class: Expression
    
    Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.
    
    This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.
    
    This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.
    
    Overrides:
    
    typeCheck in class Expression
    
    Parameters:
    visitor - an expression visitor
    contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
    
    Returns:
    the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
  - optimize
```
public Expression optimize(ExpressionVisitor visitor,
                  ContextItemStaticInfo contextItemType)
```
    Description copied from class: Expression
    
    Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.
    
    This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
    
    Overrides:
    
    optimize in class Expression
    
    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 original expression, rewritten if appropriate to optimize execution
  - computeSpecialProperties
```
public int computeSpecialProperties()
```
    Determine the special properties of this expression
    
    Overrides:
    
    computeSpecialProperties in class Expression
    
    Returns:
    StaticProperty.NON_CREATIVE.
  - evaluateItem
```
public BooleanValue evaluateItem(XPathContext c)
                          throws XPathException
```
    Description copied from class: Expression
    
    Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.
    
    Overrides:
    
    evaluateItem in class Expression
    
    Parameters:
    c - The context in which the expression is to be evaluated
    
    Returns:
    the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
    
    Throws:
    
    XPathException - if any dynamic error occurs evaluating the expression
  - getItemType
```
public ItemType getItemType()
```
    Determine the data type of the expression
    
    Specified by:
    
    getItemType in class Expression
    
    Returns:
    Type.BOOLEAN
  - computeCardinality
```
public int computeCardinality()
```
    Determine the static cardinality
    
    Specified by:
    
    computeCardinality in class Expression
    
    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
  - getIntrinsicDependencies
```
public int getIntrinsicDependencies()
```
    Get the dependencies of this expression on the context
    
    Overrides:
    
    getIntrinsicDependencies in class Expression
    
    Returns:
    a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty
  - 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
  - getImplementationMethod
```
public int getImplementationMethod()
```
    An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.
    
    Specified by:
    
    getImplementationMethod in class Expression
    
    Returns:
    the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD
  - equals
```
public boolean equals(Object other)
```
    Is this expression the same as another expression?
    
    Overrides:
    
    equals in class Object
    
    Parameters:
    other - the expression to be compared with this one
    
    Returns:
    true if the two expressions are statically equivalent
  - hashCode
```
public int hashCode()
```
    Hashcode supporting equals()
    
    Overrides:
    
    hashCode in class Object
  - export
```
public void export(ExpressionPresenter destination)
```
    Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
    
    Specified by:
    
    export in class Expression
    
    Parameters:
    destination - the expression presenter used to display the structure
  - toString
```
public String toString()
```
    The toString() method for an expression attempts to give a representation of the expression in an XPath-like form.
    
    For subclasses of Expression that represent XPath expressions, the result should always be a string that parses as an XPath 3.0 expression.
    
    Overrides:
    
    toString in class Expression
    
    Returns:
    a representation of the expression as a string
  - getStreamingAdjunct
```
protected StreamingAdjunct getStreamingAdjunct()
```
    Get a class that supports streamed evaluation of this expression
    
    Overrides:
    
    getStreamingAdjunct in class Expression
    
    Returns:
    the relevant StreamingAdjunct, or null if none is available
  - getExpressionCompiler
```
public ExpressionCompiler getExpressionCompiler()
```
    Return the compiler for the IsLast expression
    
    Overrides:
    
    getExpressionCompiler in class Expression
    
    Returns:
    the relevant ExpressionCompiler

Class IsLastExpression

Field Summary

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

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Constructor Detail

IsLastExpression

Method Detail

getCondition

typeCheck

optimize

computeSpecialProperties

evaluateItem

getItemType

computeCardinality

getIntrinsicDependencies

copy

getImplementationMethod

equals

hashCode

export

toString

getStreamingAdjunct

getExpressionCompiler