Package 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:
Serializable, SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, 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:

  • Field Details

  • Constructor Details

    • Evaluate

      public Evaluate()

  • Method Details

    • 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