net.sf.saxon.functions
Class Evaluate

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


Copyright (c) Saxonica Limited. All rights reserved.