## net.sf.saxon.functions
Class Idref

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

All Implemented Interfaces:
  Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, Locator

    public class Idref

extends SystemFunction

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
`EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, WATCH_METHOD`

Constructor Summary
`Idref()`

Method Summary
`PathMap.PathMapNodeSet` `addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)` Add a representation of a doc() call or similar function to a PathMap.
`void` `checkArguments(ExpressionVisitor visitor)` Method called during static type checking
`int` `computeSpecialProperties()` Get the static properties of this expression (other than its type).
`Expression` `copy()` Copy an expression.
`static SequenceIterator` `getIdrefMultiple(DocumentInfo doc, SequenceIterator keys, XPathContext context)` Get the result when multiple idref values are supplied.
`SequenceIterator` `iterate(XPathContext context)` Enumerate the results of the expression
`Expression` `preEvaluate(ExpressionVisitor visitor)` preEvaluate: this method suppresses compile-time evaluation by doing nothing
`Expression` `simplify(ExpressionVisitor visitor)` Simplify: add a second implicit argument, the context document
`Expression` `typeCheck(ExpressionVisitor visitor, ItemType contextItemType)` Type-check the expression.

Methods inherited from class net.sf.saxon.functions.SystemFunction
`addContextDocumentArgument, addDocToPathMap, computeCardinality, getDetails, getErrorCodeForTypeErrors, getImplementationMethod, getItemType, getRequiredType, makeSystemFunction, optimize, setDetails, useContextItemAsDefault`

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

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

`adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, 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`

Constructor Detail

### Idref

    public Idref()

Method Detail

### simplify

    public Expression simplify(ExpressionVisitor visitor)
                        throws XPathException

  Simplify: add a second implicit argument, the context document

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

### typeCheck

    public Expression typeCheck(ExpressionVisitor visitor,
                                ItemType contextItemType)
                         throws XPathException

  Type-check the expression. This also calls preEvaluate() to evaluate the function if all the arguments are constant; functions that do not require this behavior can override the preEvaluate method.

  Overrides:
    `typeCheck` in class `FunctionCall`
  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 to perform necessary run-time type checks, and to perform other type-related optimizations
  Throws:
    `XPathException` - if an error is discovered during this phase (typically a type error)

### checkArguments

    public void checkArguments(ExpressionVisitor visitor)
                        throws XPathException

  Description copied from class: `SystemFunction`
  Method called during static type checking

  Overrides:
    `checkArguments` in class `SystemFunction`
  Parameters:
    `visitor` - the expression visitor
  Throws:
    `XPathException`

### computeSpecialProperties

    public int computeSpecialProperties()

  Get the static properties of this expression (other than its type). The result is bit-signficant. 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

### preEvaluate

    public Expression preEvaluate(ExpressionVisitor visitor)

  preEvaluate: this method suppresses compile-time evaluation by doing nothing

  Overrides:
    `preEvaluate` in class `FunctionCall`
  Parameters:
    `visitor` - an expression visitor
  Returns:
    the result of the early evaluation, or the original expression, or potentially a simplified expression

### copy

    public Expression copy()

  Copy an expression. This makes a deep copy.

  Overrides:
    `copy` in class `SystemFunction`
  Returns:
    the copy of the original expression

### addToPathMap

    public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap,
                                               PathMap.PathMapNodeSet pathMapNodeSet)

  Add a representation of a doc() call or similar function to a PathMap. This is a convenience method called by the addToPathMap() methods for doc(), document(), collection() and similar functions. These all create a new root expression in the path map.

  Overrides:
    `addToPathMap` in class `Expression`
  Parameters:
    `pathMap` - the PathMap to which the expression should be added
    `pathMapNodeSet` -
  Returns:
    the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression

### iterate

    public SequenceIterator iterate(XPathContext context)
                             throws XPathException

  Enumerate the results of the expression

  Specified by:
    `iterate` in interface `SequenceIterable`
  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

### getIdrefMultiple

    public static SequenceIterator getIdrefMultiple(DocumentInfo doc,
                                                    SequenceIterator keys,
                                                    XPathContext context)
                                             throws XPathException

  Get the result when multiple idref values are supplied. Note this is also called from compiled XQuery code.

  Parameters:
    `doc` - the document to be searched
    `keys` - the idref values supplied
    `context` - the dynamic execution context
  Returns:
    iterator over the result of the function
  Throws:
    `XPathException`

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