Class ForExpression

All Implemented Interfaces:
Serializable, SourceLocator, Binding, Container, Expression, InstructionInfoProvider

public class ForExpression extends Assignation
A ForExpression maps an expression over a sequence. This version works with range variables, it doesn't change the context information
See Also:
  • Constructor Details

    • ForExpression

      public ForExpression()
  • Method Details

    • setPositionVariable

      public void setPositionVariable(RangeVariableDeclaration decl)
      Set the reference to the position variable (XQuery only)
    • getPositionVariableNameCode

      public int getPositionVariableNameCode()
    • setAction

      public void setAction(Expression action)
      Description copied from class: Assignation
      Add the "return" or "satisfies" expression, and fix up all references to the range variable that occur within that expression
      Overrides:
      setAction in class Assignation
      Parameters:
      action - the expression that occurs after the "return" keyword of a "for" expression, the "satisfies" keyword of "some/every", or the ":=" operator of a "let" expression.

      This method must be called after calling setVariableDeclaration()

    • setSlotNumber

      public void setSlotNumber(int nr)
      Set the slot number for the range variable
      Overrides:
      setSlotNumber in class Assignation
    • getRequiredSlots

      public int getRequiredSlots()
      Get the number of slots required. Normally 1, except for a FOR expression with an AT clause, where it is 2.
      Overrides:
      getRequiredSlots in class Assignation
    • typeCheck

      public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
      Type-check the expression
      Parameters:
      env - the static context of the expression
      contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
      Returns:
      the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
      Throws:
      XPathException
    • optimize

      public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException
      Optimize the expression
      Parameters:
      opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.
      env - the static context of the expression
      contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
      Returns:
      the original expression, rewritten if appropriate to optimize execution
      Throws:
      XPathException
    • convertWhereToPredicate

      public Expression convertWhereToPredicate(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException
      Convert where clause, if possible, to a predicate. Returns the converted expression if modified, or null otherwise
      Throws:
      XPathException
    • markTailFunctionCalls

      public boolean markTailFunctionCalls(int nameCode, int arity)
      Mark tail function calls: only possible if the for expression iterates zero or one times. (This arises in XSLT/XPath, which does not have a LET expression, so FOR gets used instead)
      Overrides:
      markTailFunctionCalls in class ComputedExpression
      Returns:
      true if a tail recursive call was found and if this call accounts for the whole of the value.
    • extendBindingList

      protected Binding[] extendBindingList(Binding[] in)
      Extend an array of variable bindings to include the binding(s) defined in this expression
      Overrides:
      extendBindingList in class Assignation
    • getImplementationMethod

      public int getImplementationMethod()
      An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided. This implementation provides both iterate() and process() methods natively.
      Specified by:
      getImplementationMethod in interface Expression
      Overrides:
      getImplementationMethod in class ComputedExpression
    • checkPermittedContents

      public void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) throws XPathException
      Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.
      Specified by:
      checkPermittedContents in interface Expression
      Overrides:
      checkPermittedContents in class ComputedExpression
      Parameters:
      parentType - The schema type
      env - the static context
      whole - true if this expression is expected to make the whole content of the type, false if it is expected to make up only a part
      Throws:
      XPathException - if the expression doesn't match the required content type
    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Iterate over the sequence of values
      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
    • process

      public void process(XPathContext context) throws XPathException
      Process this expression as an instruction, writing results to the current outputter
      Specified by:
      process in interface Expression
      Overrides:
      process in class ComputedExpression
      Parameters:
      context - The dynamic context, giving access to the current node, the current variables, etc.
      Throws:
      XPathException
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Determine the data type of the items returned by the expression, if possible
      Parameters:
      th -
      Returns:
      one of the values Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)
    • computeCardinality

      public int computeCardinality()
      Determine the static cardinality of the expression
      Specified by:
      computeCardinality in class ComputedExpression
    • display

      public void display(int level, PrintStream out, Configuration config)
      Diagnostic print of expression structure
      Parameters:
      level - indentation level for this expression
      out - Output destination
      config -
    • getConstructType

      protected int getConstructType()
      Get the type of this expression for use in tracing and diagnostics
      Overrides:
      getConstructType in class ComputedExpression
      Returns:
      the type of expression, as enumerated in class Location