## net.sf.saxon.functions
Class Evaluate

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

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

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.ComputedExpression
`locationId, staticProperties`

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

Constructor Summary
`Evaluate()`

Method Summary
`void` `checkArguments(StaticContext env)` 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(StaticContext env)` preEvaluate: this method suppresses compile-time evaluation by doing nothing (because the value of the expression depends on the runtime context)

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

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

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

`adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getImplementationMethod, getInstructionInfo, getLineNumber, getLocationId, getParentExpression, getPublicId, getSpecialProperties, getSystemId, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, typeError, typeError`

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

### checkArguments

    public void checkArguments(StaticContext env)
                        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`
  Throws:
    `XPathException`

### preEvaluate

    public Expression preEvaluate(StaticContext env)
                           throws XPathException

  preEvaluate: 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`
  Throws:
    `XPathException`

### evaluateItem

    public Item evaluateItem(XPathContext c)
                      throws XPathException

  Evaluate in a general context

  Specified by:
    `evaluateItem` in interface `Expression`
  Overrides:
    `evaluateItem` in class `ComputedExpression`
  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 `Expression`
  Overrides:
    `iterate` in class `ComputedExpression`
  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 `ComputedExpression`
  Returns:
    a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty