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## net.sf.saxon.functions
Class Evaluate

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

All Implemented Interfaces:
  java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, org.xml.sax.Locator

    public class Evaluate

extends SystemFunction

This class implements the saxon:evaluate(), saxon:expression(), and saxon:eval() extension functions, which are specially-recognized by the system because they need access to parts of the static context

See Also:
  Serialized Form

Nested Class Summary
`static class` | `Evaluate.PreparedExpression` Inner class PreparedExpression represents a compiled XPath expression together with the standard variables $p1 ..

Field Summary
`static int` | `EVAL`
`static int` | `EVALUATE`
`static int` | `EVALUATE_NODE`
`static int` | `EXPRESSION`

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, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties`

Constructor Summary
`Evaluate()`

Method Summary
`PathMap.PathMapNodeSet` | `addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)` Add a representation of this expression to a PathMap.
`void` | `checkArguments(ExpressionVisitor visitor)` Method supplied by each class of function to check arguments during parsing, when all the argument expressions have been read
`Item` | `evaluateItem(XPathContext c)` Evaluate in a general context
`int` | `getIntrinsicDependencies()` Determine the dependencies
`protected SequenceType` | `getRequiredType(int arg)` Get the required type of the nth argument
`SequenceIterator` | `iterate(XPathContext c)` Iterate over the results of the function
`Expression` | `preEvaluate(ExpressionVisitor visitor)` preEvaluate: for saxon:expression, if the expression is known at compile time, then it is compiled at compile time.

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

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

Methods inherited from class net.sf.saxon.expr.Expression
`adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError`

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

Field Detail

### EVALUATE

    public static final int EVALUATE

See Also:
  Constant Field Values

### EXPRESSION

    public static final int EXPRESSION

See Also:
  Constant Field Values

### EVAL

    public static final int EVAL

See Also:
  Constant Field Values

### EVALUATE_NODE

    public static final int EVALUATE_NODE

See Also:
  Constant Field Values

Constructor Detail

### Evaluate

    public Evaluate()

Method Detail

### getRequiredType

    protected SequenceType getRequiredType(int arg)

  Get the required type of the nth argument

  Overrides:
    `getRequiredType` in class `SystemFunction`
  Parameters:
    `arg` - the number of the argument whose type is requested, zero-based
  Returns:
    the required type of the argument as defined in the function signature

### checkArguments

    public void checkArguments(ExpressionVisitor visitor)
                        throws XPathException

  Method supplied by each class of function to check arguments during parsing, when all the argument expressions have been read

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

### preEvaluate

    public Expression preEvaluate(ExpressionVisitor visitor)
                           throws XPathException

  preEvaluate: for saxon:expression, if the expression is known at compile time, then it is compiled at compile time. In other cases this method suppresses compile-time evaluation by doing nothing (because the value of the expression depends on the runtime context).

  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
  Throws:
    `XPathException`

### addToPathMap

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

  Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.

  The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.

  This particular implementation has to deal with the fact that saxon:evaluate() and related functions can navigate anywhere in the tree.

  Overrides:
    `addToPathMap` in class `Expression`
  Parameters:
    `pathMap` - the PathMap to which the expression should be added
    `pathMapNodeSet` - the PathMapNodeSet to which the paths embodied in this expression should be added
  Returns:
    the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.

### evaluateItem

    public Item evaluateItem(XPathContext c)
                      throws XPathException

  Evaluate in a general context

  Specified by:
    `evaluateItem` in interface `EvaluableItem`
  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

### iterate

    public SequenceIterator iterate(XPathContext c)
                             throws XPathException

  Iterate over the results of the function

  Specified by:
    `iterate` in interface `SequenceIterable`
  Overrides:
    `iterate` in class `Expression`
  Parameters:
    `c` - 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

### getIntrinsicDependencies

    public int getIntrinsicDependencies()

  Determine the dependencies

  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

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