Package net.sf.saxon.expr.instruct

Class LocalParam

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.instruct.Instruction
net.sf.saxon.expr.instruct.LocalParam
All Implemented Interfaces:
Binding, ExportAgent, LocalBinding, Locatable, IdentityComparable, Traceable
public final class LocalParam extends Instruction implements LocalBinding
The compiled form of an xsl:param element within a template in an XSLT stylesheet.

The xsl:param element in XSLT has mandatory attribute name and optional attribute select. It can also be specified as required="yes" or required="no".

This is used only for parameters to XSLT templates. For function calls, the caller of the function places supplied arguments onto the callee's stackframe and the callee does not need to do anything. Global parameters (XQuery external variables) are handled using GlobalParam.

The LocalParam class is also used to represent parameters with the saxon:iterate instruction

Changed in Saxon 9.8 to combine the previously-separate LocalParamSetter and LocalParam classes into one

  • Constructor Details

    • LocalParam

      public LocalParam()

  • Method Details

    • 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

    • 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

    • 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.

    • isAssignable

      public boolean isAssignable()
      Description copied from interface: Binding
      Test whether it is permitted to assign to the variable using the saxon:assign extension element. This will only be for an XSLT global variable where the extra attribute saxon:assignable="yes" is present.
      Specified by:
      isAssignable in interface Binding
      Returns:
      true if the binding is assignable

    • 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 LocalBinding
      Returns:
      the slot number on the local stack frame

    • isRequiredParam

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

    • isImplicitlyRequiredParam

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

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo 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.

      Overrides:
      typeCheck in class Expression
      Parameters:
      visitor - an expression visitor
      contextItemType - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
      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)

    • computeEvaluationMode

      public void computeEvaluationMode()

    • copy

      public LocalParam copy(RebindingMap rebindings)
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Parameters:
      rebindings - a mutable list of (old binding, new binding) pairs that is used to update the bindings held in any local variable references that are copied.
      Returns:
      the copy of the original expression

    • addReference

      public void addReference(VariableReference ref, boolean isLoopingReference)
      Description copied from interface: Binding
      Register a variable reference that refers to the variable bound in this expression
      Specified by:
      addReference in interface Binding
      Parameters:
      ref - the variable reference
      isLoopingReference - - true if the reference occurs within a loop, such as the predicate of a filter expression

    • checkAgainstRequiredType

      public void checkAgainstRequiredType(ExpressionVisitor visitor) throws XPathException
      Check the select expression against the required type.
      Parameters:
      visitor - an expression visitor
      Throws:
      XPathException - if the check fails

    • 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)

    • setConversion

      public void setConversion(Expression convertor)
      Define a conversion that is to be applied to the supplied parameter value.
      Parameters:
      convertor - The expression to be applied. This performs type checking, and the basic conversions implied by function calling rules, for example numeric promotion, atomization, and conversion of untyped atomic values to a required type. The conversion uses the actual parameter value as input, referencing it using a VariableReference. The argument can be null to indicate that no conversion is required.

    • getConversion

      public Expression getConversion()
      Get the conversion expression
      Returns:
      the expression used to convert the value to the required type, or null if there is none

    • getInstructionNameCode

      public int getInstructionNameCode()
      Get the name of this instruction for diagnostic and tracing purposes
      Overrides:
      getInstructionNameCode in class Instruction
      Returns:
      the integer name code

    • operands

      public Iterable<Operand> operands()
      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)
      Specified by:
      operands in class Instruction
      Returns:
      an iterator over the subexpressions

    • getIntegerBoundsForVariable

      public IntegerValue[] getIntegerBoundsForVariable()
      If the variable is bound to an integer, get the minimum and maximum possible values. Return null if unknown or not applicable
      Specified by:
      getIntegerBoundsForVariable in interface Binding
      Returns:
      a pair of integers containing the minimum and maximum values for the integer value; or null if the value is not an integer or the range is unknown

    • evaluateVariable

      public Sequence evaluateVariable(XPathContext c)
      Evaluate the variable
      Specified by:
      evaluateVariable in interface Binding
      Parameters:
      c - the XPath dynamic evaluation context
      Returns:
      the result of evaluating the variable

    • isCompatible

      public boolean isCompatible(LocalParam other)
      Check if parameter is compatible with another
      Parameters:
      other - - the LocalParam object to compare
      Returns:
      result of the compatibility check

    • isLiftable

      public boolean isLiftable(boolean forStreaming)
      Ask whether the expression can be lifted out of a loop, assuming it has no dependencies on the controlling variable/focus of the loop
      Overrides:
      isLiftable in class Expression
      Parameters:
      forStreaming - true if compiling streamable code
      Returns:
      true if the expression can be loop lifted

    • hasVariableBinding

      public boolean hasVariableBinding(Binding binding)
      Ask whether this expression is, or contains, the binding of a given variable
      Overrides:
      hasVariableBinding in class Expression
      Parameters:
      binding - the variable binding
      Returns:
      true if this expression is the variable binding (for example a ForExpression or LetExpression) or if it is a FLWOR expression that binds the variable in one of its clauses.

    • getItemType

      public ItemType getItemType()
      Get the item type of the items returned by evaluating this instruction
      Overrides:
      getItemType in class Instruction
      Returns:
      the static item type of the instruction

    • computeCardinality

      protected int computeCardinality()
      Get the cardinality of the sequence returned by evaluating this instruction
      Overrides:
      computeCardinality in class Instruction
      Returns:
      the static cardinality

    • computeSpecialProperties

      protected int computeSpecialProperties()
      Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.
      Overrides:
      computeSpecialProperties in class Instruction
      Returns:
      a set of flags indicating static properties of this expression

    • mayCreateNewNodes

      public boolean mayCreateNewNodes()
      Determine whether this instruction creates new nodes. This implementation returns a default value of false
      Overrides:
      mayCreateNewNodes in class Instruction
      Returns:
      true if the instruction creates new nodes (or if it can't be proved that it doesn't)

    • getExpressionName

      public String getExpressionName()
      Get a name identifying the kind of expression, in terms meaningful to a user.
      Overrides:
      getExpressionName in class Instruction
      Returns:
      a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.

    • toShortString

      public String toShortString()
      Produce a short string identifying the expression for use in error messages
      Overrides:
      toShortString in class Expression
      Returns:
      a short string, sufficient to identify the expression

    • export

      public void export(ExpressionPresenter out) throws XPathException
      Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
      Specified by:
      export in interface ExportAgent
      Specified by:
      export in class Expression
      Parameters:
      out - the expression presenter used to display the structure
      Throws:
      XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

    • setIndexedVariable

      public void setIndexedVariable()
      Say that the bound value has the potential to be indexed
      Specified by:
      setIndexedVariable in interface LocalBinding

    • isIndexedVariable

      public boolean isIndexedVariable()
      Ask whether the binding is to be indexed
      Specified by:
      isIndexedVariable in interface LocalBinding
      Returns:
      true if the variable value can be indexed

    • getElaborator

      public Elaborator getElaborator()
      Make an elaborator for this expression
      Overrides:
      getElaborator in class Expression
      Returns:
      an appropriate Elaborator