Constructor Detail

• IterateInstr

  public IterateInstr​(Expression select,
                      Expression action,
                      Expression finallyExp)

  Create a saxon:iterate instruction

  Parameters:

  select - the select expression

  action - the body of the saxon:iterate loop

  finallyExp - the expression to be evaluated before final completion, may be null

Method Detail

• getActionExpression

  public Expression getActionExpression()

  Get the action expression (the content of the for-each)

  Returns:

  the body of the for-each loop

• simplify

  public Expression simplify​(ExpressionVisitor visitor)
                      throws XPathException

  Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression).

  Specified by:

  simplify in class Instruction

  Parameters:

  visitor - the expression visitor

  Returns:

  the simplified expression

  Throws:

  XPathException - if an error is discovered during expression rewriting

• typeCheck

  public Expression typeCheck​(ExpressionVisitor visitor,
                              ItemType contextItemType)
                       throws XPathException

  Type-check the expression

  Overrides:

  typeCheck in class Expression

  Parameters:

  visitor - an expression visitor

  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 - if an error is discovered during this phase (typically a type error)

• optimize

  public Expression optimize​(ExpressionVisitor visitor,
                             ItemType contextItemType)
                      throws XPathException

  Description copied from class: Expression
  Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

  This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

  Overrides:

  optimize in class Expression

  Parameters:

  visitor - an expression visitor

  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 - if an error is discovered during this phase (typically a type error)

• getItemType

  public final ItemType getItemType​(TypeHierarchy th)

  Determine the data type of the items returned by this expression

  Overrides:

  getItemType in class Instruction

  Parameters:

  th - the type hierarchy cache

  Returns:

  the data type

• createsNewNodes

  public final boolean createsNewNodes()

  Determine whether this instruction creates new nodes. This implementation returns true if the "action" creates new nodes. (Nodes created by the condition can't contribute to the result).

  Overrides:

  createsNewNodes in class Instruction

  Returns:

  true if the instruction creates new nodes (or if it can't be proved that it doesn't)

• 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.

  Overrides:

  addToPathMap in class Expression

  Parameters:

  pathMap - the PathMap to which the expression should be added

  pathMapNodeSet - the set of nodes in the path map that are affected

  Returns:

  the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter 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.

• computeDependencies

  public int computeDependencies()

  Compute the dependencies of an expression, as the union of the dependencies of its subexpressions. (This is overridden for path expressions and filter expressions, where the dependencies of a subexpression are not all propogated). This method should be called only once, to compute the dependencies; after that, getDependencies should be used.

  Overrides:

  computeDependencies in class Expression

  Returns:

  the depencies, as a bit-mask

• promoteInst

  protected void promoteInst​(PromotionOffer offer)
                      throws XPathException

  Handle promotion offers, that is, non-local tree rewrites.

  Overrides:

  promoteInst in class Instruction

  Parameters:

  offer - The type of rewrite being offered

  Throws:

  XPathException

• iterateSubExpressions

  public java.util.Iterator iterateSubExpressions()

  Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)

  Overrides:

  iterateSubExpressions in class Expression

  Returns:

  an iterator containing the sub-expressions of this expression

• hasLoopingSubexpression

  public boolean hasLoopingSubexpression​(Expression child)

  Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedly

  Overrides:

  hasLoopingSubexpression in class Expression

  Parameters:

  child - the immediate subexpression

  Returns:

  true if the child expression is evaluated repeatedly

• replaceSubExpression

  public boolean replaceSubExpression​(Expression original,
                                      Expression replacement)

  Replace one subexpression by a replacement subexpression

  Overrides:

  replaceSubExpression in class Expression

  Parameters:

  original - the original subexpression

  replacement - the replacement subexpression

  Returns:

  true if the original subexpression is found

• 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.

  Overrides:

  getImplementationMethod in class Instruction

  Returns:

  the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

• 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.

  Overrides:

  checkPermittedContents in class Expression

  Parameters:

  parentType - the "given complex type": the method is checking that the nodes returned by this expression are acceptable members of the content model of this type

  env - the static context

  whole - if true, we want to check that the value of this expression satisfies the content model as a whole; if false we want to check that the value of the expression is acceptable as one part of the content

  Throws:

  XPathException - if the value delivered by this expression cannot be part of the content model of the given type

• copy

  public Expression copy()

  Copy an expression. This makes a deep copy.

  Specified by:

  copy in class Expression

  Returns:

  the copy of the original expression

• processLeavingTail

  public TailCall processLeavingTail​(XPathContext context)
                              throws XPathException

  Description copied from class: Instruction
  ProcessLeavingTail: called to do the real work of this instruction. This method must be implemented in each subclass. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.

  Specified by:

  processLeavingTail in interface TailCallReturner

  Specified by:

  processLeavingTail in class Instruction

  Parameters:

  context - The dynamic context of the transformation, giving access to the current node, the current variables, etc.

  Returns:

  null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.

  Throws:

  XPathException

• explain

  public void explain​(ExpressionPresenter out)

  Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

  Specified by:

  explain in class Expression

  Parameters:

  out - the expression presenter used to display the structure