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## net.sf.saxon.functions
Class KeyFn

    java.lang.Object
      net.sf.saxon.expr.ComputedExpression
          net.sf.saxon.expr.FunctionCall
              net.sf.saxon.functions.SystemFunction
                  net.sf.saxon.functions.KeyFn

All Implemented Interfaces:
  Container, Expression, InstructionInfoProvider, java.io.Serializable, javax.xml.transform.SourceLocator, XSLTFunction

public class KeyFn
extends SystemFunction
implements XSLTFunction

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.ComputedExpression
`locationId, staticProperties`

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

Constructor Summary
`KeyFn()`

Method Summary
`void` | `checkArguments(StaticContext env)` Method called during static type checking
`int` | `computeSpecialProperties()` Get the static properties of this expression (other than its type).
`static KeyFn` | `internalKeyCall(NamePool pool, int fingerprint, java.lang.String name, Expression value, Expression doc)` Non-standard constructor to create an internal call on key() with a known key fingerprint
`SequenceIterator` | `iterate(XPathContext context)` Enumerate the results of the expression
`Expression` | `preEvaluate(StaticContext env)` preEvaluate: this method suppresses compile-time evaluation by doing nothing
`Expression` | `simplify(StaticContext env)` Simplify: add a third implicit argument, the context document

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

Methods inherited from class net.sf.saxon.expr.FunctionCall
`checkArgumentCount, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, optimize, promote, setArguments, setFunctionNameCode, simplifyArguments, typeCheck`

Methods inherited from class net.sf.saxon.expr.ComputedExpression
`adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, suppressValidation, typeError, typeError`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### KeyFn

    public KeyFn()

Method Detail

### internalKeyCall

    public static KeyFn internalKeyCall(NamePool pool,
                                        int fingerprint,
                                        java.lang.String name,
                                        Expression value,
                                        Expression doc)

  Non-standard constructor to create an internal call on key() with a known key fingerprint

### simplify

    public Expression simplify(StaticContext env)
                        throws XPathException

  Simplify: add a third implicit argument, the context document

  Specified by:
    `simplify` in interface `Expression`
  Overrides:
    `simplify` in class `FunctionCall`
  Throws:
    `XPathException`

### checkArguments

    public void checkArguments(StaticContext env)
                        throws XPathException

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

  Overrides:
    `checkArguments` in class `SystemFunction`
  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 a property bit is set, it is true, but if it is unset, the value is unknown.

  Overrides:
    `computeSpecialProperties` in class `SystemFunction`

### preEvaluate

    public Expression preEvaluate(StaticContext env)

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

  Overrides:
    `preEvaluate` in class `FunctionCall`

### iterate

    public SequenceIterator iterate(XPathContext context)
                             throws XPathException

  Enumerate the results of the expression

  Specified by:
    `iterate` in interface `Expression`
  Overrides:
    `iterate` in class `ComputedExpression`
  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

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