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## net.sf.saxon.functions
Class Subsequence

    java.lang.Object
      net.sf.saxon.expr.Expression
          net.sf.saxon.expr.FunctionCall
              net.sf.saxon.functions.SystemFunction
                  net.sf.saxon.functions.Subsequence

All Implemented Interfaces:
  Serializable, SourceLocator, LocationProvider, SaxonLocator, CallableExpression, InstructionInfo, Locator

    public class Subsequence

extends SystemFunction
implements CallableExpression

Implements the XPath 2.0 subsequence() function

See Also:
  Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.functions.SystemFunction
`operation`

Fields inherited from class net.sf.saxon.expr.FunctionCall
`argument`

Fields inherited from class net.sf.saxon.expr.Expression
`EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD`

Constructor Summary
`Subsequence()`

Method Summary
`SequenceIterator` | `call(SequenceIterator[] arguments, XPathContext context)` Evaluate the expression
`int` | `computeCardinality()` Determine the cardinality of the function.
`int` | `computeSpecialProperties()` Get the static properties of this expression (other than its type).
`ItemType` | `getItemType(TypeHierarchy th)` Determine the data type of the items in the sequence
`SequenceIterator` | `iterate(XPathContext context)` Evaluate the function to return an iteration of selected nodes.
`Expression` | `optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Perform optimisation of an expression and its subexpressions.
`static SequenceIterator` | `subSequence(SequenceIterator seq, NumericValue startVal, NumericValue lengthVal, XPathContext context)`

Methods inherited from class net.sf.saxon.functions.SystemFunction
`addContextDocumentArgument, addDocToPathMap, checkArguments, copy, equals, getDetails, getErrorCodeForTypeErrors, getImplementationMethod, getOperation, getRequiredType, makeSystemFunction, setDetails, useContextItemAsDefault`

Methods inherited from class net.sf.saxon.expr.FunctionCall
`addExternalFunctionCallToPathMap, checkArgumentCount, explain, getArguments, getDisplayName, getExpressionName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionName, simplify, simplifyArguments, toString, typeCheck`

Methods inherited from class net.sf.saxon.expr.Expression
`addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, 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.CallableExpression
`getArguments`

Constructor Detail

### Subsequence

    public Subsequence()

Method Detail

### getItemType

    public ItemType getItemType(TypeHierarchy th)

  Determine the data type of the items in the sequence

  Overrides:
    `getItemType` in class `SystemFunction`
  Parameters:
    `th` - the type hierarchy cache
  Returns:
    the type of the argument

### 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 `SystemFunction`
  Returns:
    the special properties, as a bit-significant integer

### computeCardinality

    public int computeCardinality()

  Determine the cardinality of the function.

  Overrides:
    `computeCardinality` in class `SystemFunction`
  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`

### optimize

    public Expression optimize(ExpressionVisitor visitor,
                               ExpressionVisitor.ContextItemType contextItemType)
                        throws XPathException

  Perform optimisation of an expression and its subexpressions.

  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 `SystemFunction`
  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
  Throws:
    `XPathException` - if an error is discovered during this phase (typically a type error)

### iterate

    public SequenceIterator iterate(XPathContext context)
                             throws XPathException

  Evaluate the function to return an iteration of selected nodes.

  Overrides:
    `iterate` in class `Expression`
  Parameters:
    `context` - supplies the context for evaluation
  Returns:
    a SequenceIterator that can be used to iterate over the result of the expression
  Throws:
    `XPathException` - if any dynamic error occurs evaluating the expression

### call

    public SequenceIterator call(SequenceIterator[] arguments,
                                 XPathContext context)
                          throws XPathException

  Description copied from interface: `CallableExpression`
  Evaluate the expression

  Specified by:
    `call` in interface `CallableExpression`
  Parameters:
    `arguments` - the values of the arguments, supplied as SequenceIterators
    `context` - the dynamic evaluation context
  Returns:
    the result of the evaluation, in the form of a SequenceIterator
  Throws:
    `XPathException` - if a dynamic error occurs during the evaluation of the expression

### subSequence

    public static SequenceIterator subSequence(SequenceIterator seq,
                                               NumericValue startVal,
                                               NumericValue lengthVal,
                                               XPathContext context)
                                        throws XPathException

  Throws:
    `XPathException`

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Copyright (c) 2004-2011 Saxonica Limited. All rights reserved.