Class GeneralVariable

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, Binding, EvaluableItem, SequenceIterable, TailCallReturner, InstructionInfo, Locator
Direct Known Subclasses:
Assign, GlobalVariable, LocalParam, LocalVariable, WithParam

public abstract class GeneralVariable extends Instruction implements Binding
This class defines common behaviour across xsl:variable, xsl:param, and xsl:with-param; also saxon:assign
See Also:
  • Field Details

    • variableQName

      protected StructuredQName variableQName
    • slotNumber

      protected int slotNumber
    • referenceCount

      protected int referenceCount
    • evaluationMode

      protected int evaluationMode
  • Constructor Details

    • GeneralVariable

      public GeneralVariable()
      Create a general variable
  • Method Details

    • init

      public void init(Expression select, StructuredQName qName)
      Initialize the properties of the variable
      Parameters:
      select - the expression to which the variable is bound
      qName - the name of the variable
    • setSelectExpression

      public void setSelectExpression(Expression select)
      Set the expression to which this variable is bound
      Parameters:
      select - the initializing expression
    • getSelectExpression

      public Expression getSelectExpression()
      Get the expression to which this variable is bound
      Returns:
      the initializing expression
    • setRequiredType

      public void setRequiredType(SequenceType required)
      Set the required type of this variable
      Parameters:
      required - the required type
    • getRequiredType

      public SequenceType getRequiredType()
      Get the required type of this variable
      Specified by:
      getRequiredType in interface Binding
      Returns:
      the required type
    • setAssignable

      public void setAssignable(boolean assignable)
      Indicate whether this variable is assignable using saxon:assign
      Parameters:
      assignable - true if this variable is assignable
    • setRequiredParam

      public void setRequiredParam(boolean requiredParam)
      Indicate that this variable represents a required parameter
      Parameters:
      requiredParam - true if this is a required parameter
    • setImplicitlyRequiredParam

      public void setImplicitlyRequiredParam(boolean requiredParam)
      Indicate that this variable represents a parameter that is implicitly required (because there is no usable default value)
      Parameters:
      requiredParam - true if this is an implicitly required parameter
    • setTunnel

      public void setTunnel(boolean tunnel)
      Indicate whether this variable represents a tunnel parameter
      Parameters:
      tunnel - true if this is a tunnel parameter
    • setReferenceCount

      public void setReferenceCount(int refCount)
      Set the nominal number of references to this variable
      Parameters:
      refCount - the nominal number of references
    • getEvaluationMode

      public int getEvaluationMode()
      Get the evaluation mode of the variable
      Returns:
      the evaluation mode (a constant in ExpressionTool
    • isAssignable

      public final boolean isAssignable()
      Test whether it is permitted to assign to the variable using the saxon:assign extension element. This will only be true if the extra attribute saxon:assignable="yes" is present.
      Specified by:
      isAssignable in interface Binding
      Returns:
      true if the binding is assignable
    • getItemType

      public ItemType getItemType(TypeHierarchy th)
      Get the type of the result of this instruction. An xsl:variable instruction returns nothing, so the type is empty.
      Overrides:
      getItemType in class Instruction
      Parameters:
      th - the type hierarchy cache
      Returns:
      the empty type.
    • getCardinality

      public int getCardinality()
      Get the cardinality of the result of this instruction. An xsl:variable instruction returns nothing, so the type is empty.
      Overrides:
      getCardinality in class Expression
      Returns:
      the empty cardinality.
    • isGlobal

      public boolean isGlobal()
      Description copied from interface: Binding
      Indicate whether the binding is local or global. A global binding is one that has a fixed value for the life of a query or transformation; any other binding is local.
      Specified by:
      isGlobal in interface Binding
      Returns:
      true if the binding is global
    • getLocalSlotNumber

      public int getLocalSlotNumber()
      If this is a local variable held on the local stack frame, return the corresponding slot number. In other cases, return -1.
      Specified by:
      getLocalSlotNumber in interface Binding
      Returns:
      the slot number on the local stack frame
    • isRequiredParam

      public final boolean isRequiredParam()
      Ask whether this variable represents a required parameter
      Returns:
      true if this is a required parameter
    • isImplicitlyRequiredParam

      public final boolean isImplicitlyRequiredParam()
      Ask whether this variable represents a parameter that is implicitly required, because there is no usable default value
      Returns:
      true if this variable is an implicitly required parameter
    • isTunnelParam

      public final boolean isTunnelParam()
      Ask whether this variable represents a tunnel parameter
      Returns:
      true if this is a tunnel parameter
    • getInstructionNameCode

      public int getInstructionNameCode()
      Get the name of this instruction (that is xsl:variable, xsl:param etc) for diagnostics
      Overrides:
      getInstructionNameCode in class Instruction
      Returns:
      the name of this instruction, as a name pool name code
    • simplify

      public Expression simplify(ExpressionVisitor visitor) throws XPathException
      Simplify this expression
      Specified by:
      simplify in class Instruction
      Parameters:
      visitor - an expression
      Returns:
      the simplified expression
      Throws:
      XPathException
    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
      Description copied from class: Expression
      Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

      This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

      If the implementation returns a value other than "this", then it is required to ensure that the parent pointer and location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

      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)
    • 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
    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.
      Specified by:
      evaluateItem in interface EvaluableItem
      Overrides:
      evaluateItem in class Instruction
      Parameters:
      context - 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 context) throws XPathException
      Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation relies on the process() method: it "pushes" the results of the instruction to a sequence in memory, and then iterates over this in-memory sequence. In principle instructions should implement a pipelined iterate() method that avoids the overhead of intermediate storage.
      Specified by:
      iterate in interface SequenceIterable
      Overrides:
      iterate in class Instruction
      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
    • getSelectValue

      public ValueRepresentation getSelectValue(XPathContext context) throws XPathException
      Evaluate the variable. That is, get the value of the select expression if present or the content of the element otherwise, either as a tree or as a sequence
      Parameters:
      context - the XPath dynamic context
      Returns:
      the result of evaluating the variable
      Throws:
      XPathException
    • 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 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
    • 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
    • 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
    • getSlotNumber

      public int getSlotNumber()
      Get the slot number allocated to this variable
      Returns:
      the slot number, that is the position allocated to the variable on its stack frame
    • setSlotNumber

      public void setSlotNumber(int s)
      Set the slot number of this variable
      Parameters:
      s - the slot number, that is, the position allocated to this variable on its stack frame
    • setVariableQName

      public void setVariableQName(StructuredQName s)
      Set the name of the variable
      Parameters:
      s - the name of the variable (a QName)
    • getVariableQName

      public StructuredQName getVariableQName()
      Get the name of this variable
      Specified by:
      getVariableQName in interface Binding
      Returns:
      the name of this variable (a QName)