IndexedLookupExpression

java.lang.Object
- net.sf.saxon.expr.Expression
- - com.saxonica.ee.optim.IndexedLookupExpression

All Implemented Interfaces:

IdentityComparable
```
public final class IndexedLookupExpression
extends Expression
```
An IndexedLookupExpression contains a base expression and a lookup expression. The base expression will always be a variable reference. The expression returns true if the base expression (after atomization) contains the value of the lookup expression. That is, the expression is equivalent to exists(base[lookup]), except that lookup is evaluated with the same context as base.

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
`IndexedLookupExpression(VariableReference base, Expression lookup, AtomicComparer comparer)` Constructor

Method Summary

Methods
Modifier and Type	Method and Description
`int`	`computeCardinality()` Get the static cardinality of this expression
`int`	`computeDependencies()` Determine which aspects of the context the expression depends on.
`int`	`computeSpecialProperties()` Get the static properties of this expression (other than its type).
`Expression`	`copy()` Copy an expression.
`boolean`	`effectiveBooleanValue(XPathContext context)` Get the effective boolean value of the expression.
`boolean`	`equals(Object other)` Is this expression the same as another expression?
`Item`	`evaluateItem(XPathContext context)` Evaluate an expression as a single item.
`void`	`export(ExpressionPresenter destination)` Diagnostic print of expression structure.
`AtomicComparer`	`getAtomicComparer()` Get the atomic comparer used
`VariableReference`	`getBase()`
`VariableReference`	`getBaseExpression()` Get the underlying expression
`ExpressionCompiler`	`getExpressionCompiler()` Return the compiler of the IndexedLookup expression
`int`	`getImplementationMethod()` An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
`ItemType`	`getItemType()` Get the data type of the items returned
`Expression`	`getLookup()` Get the lookup expression
`Expression`	`getUseExpression()` Get the expression that computes the key
`int`	`hashCode()` get HashCode for comparing two expressions
`Iterable<Operand>`	`operands()` Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
`Expression`	`promote(PromotionOffer offer)` Promote this expression if possible
`void`	`setBase(VariableReference base)`
`void`	`setLookup(Expression lookup)`
`Expression`	`typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)` Type-check the expression

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

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

- Constructor Detail
  - IndexedLookupExpression
```
public IndexedLookupExpression(VariableReference base,
                       Expression lookup,
                       AtomicComparer comparer)
```
    Constructor
    
    Parameters:
    base - A sequence expression denoting the sequence to be searched
    lookup - An expression defining value to be sought
    comparer - Comparison algorithm for comparing values
- Method Detail
  - operands
```
public Iterable<Operand> operands()
```
    Description copied from class: Expression
    
    Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression. Default implementation works off the results of iterateSubExpressions()
    If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.
    
    Overrides:
    
    operands in class Expression
    
    Returns:
    an iterator containing the sub-expressions of this expression
  - getBase
```
public VariableReference getBase()
```
  - setBase
```
public void setBase(VariableReference base)
```
  - setLookup
```
public void setLookup(Expression lookup)
```
  - getLookup
```
public Expression getLookup()
```
    Get the lookup expression
    
    Returns:
    the expression acting as the filter predicate
  - getItemType
```
public ItemType getItemType()
```
    Get the data type of the items returned
    
    Specified by:
    
    getItemType in class Expression
    
    Returns:
    an integer representing the data type
  - getBaseExpression
```
public VariableReference getBaseExpression()
```
    Get the underlying expression
    
    Returns:
    the expression being filtered
  - getUseExpression
```
public Expression getUseExpression()
```
    Get the expression that computes the key
    
    Returns:
    the expression that computes the key
  - getAtomicComparer
```
public AtomicComparer getAtomicComparer()
```
    Get the atomic comparer used
    
    Returns:
    the atomic comparer
  - typeCheck
```
public Expression typeCheck(ExpressionVisitor visitor,
                   ContextItemStaticInfo contextInfo)
```
    Type-check the expression
    
    Overrides:
    
    typeCheck in class Expression
    
    Parameters:
    visitor - an expression visitor
    contextInfo - information about the existence and type of the context item
    
    Returns:
    the expression after type-checking (potentially modified to add run-time checks and/or conversions)
  - 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
  - promote
```
public Expression promote(PromotionOffer offer)
                   throws XPathException
```
    Promote this expression if possible
    
    Overrides:
    
    promote in class Expression
    
    Parameters:
    offer - details of the promotion that is possible
    
    Returns:
    the promoted expression (or the original expression, unchanged)
    
    Throws:
    
    XPathException - if any error is detected
  - computeCardinality
```
public int computeCardinality()
```
    Get the static cardinality of this expression
    
    Specified by:
    
    computeCardinality in class Expression
    
    Returns:
    the cardinality. The method attempts to determine the case where the filter predicate is guaranteed to select at most one item from the sequence being filtered
  - computeSpecialProperties
```
public int computeSpecialProperties()
```
    Get the static properties of this expression (other than its type). The result is bit-significant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.
    
    Overrides:
    
    computeSpecialProperties in class Expression
    
    Returns:
    the static properties of the expression, as a bit-significant value
  - getImplementationMethod
```
public int getImplementationMethod()
```
    Description copied from class: Expression
    
    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()
```
    get HashCode for comparing two expressions
    
    Overrides:
    
    hashCode in class Object
    
    Returns:
    the hash code
  - effectiveBooleanValue
```
public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException
```
    Description copied from class: Expression
    
    Get the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.
    
    Overrides:
    
    effectiveBooleanValue in class Expression
    
    Parameters:
    context - The context in which the expression is to be evaluated
    
    Returns:
    the effective boolean value
    
    Throws:
    
    XPathException - if any dynamic error occurs evaluating the expression
  - evaluateItem
```
public Item evaluateItem(XPathContext context)
                  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:
    context - 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
  - computeDependencies
```
public int computeDependencies()
```
    Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and XPathContext.CURRENT_NODE
    
    Overrides:
    
    computeDependencies in class Expression
    
    Returns:
    the dependencies
  - getExpressionCompiler
```
public ExpressionCompiler getExpressionCompiler()
```
    Return the compiler of the IndexedLookup expression
    
    Overrides:
    
    getExpressionCompiler in class Expression
    
    Returns:
    the relevant ExpressionCompiler
  - 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

Class IndexedLookupExpression

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

IndexedLookupExpression

Method Detail

operands

getBase

setBase

setLookup

getLookup

getItemType

getBaseExpression

getUseExpression

getAtomicComparer

typeCheck

copy

promote

computeCardinality

computeSpecialProperties

getImplementationMethod

equals

hashCode

effectiveBooleanValue

evaluateItem

computeDependencies

getExpressionCompiler

export