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, TailCallReturner, LocalBinding, Locatable, IdentityComparable
```
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

Field Summary

Fields
Modifier and Type Field and Description

protected Evaluator evaluator

protected int referenceCount

protected int slotNumber

protected StructuredQName variableQName
- Fields inherited from class net.sf.saxon.expr.Expression
  EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Fields
Modifier and Type	Field and Description
`protected Evaluator`	`evaluator`
`protected int`	`referenceCount`
`protected int`	`slotNumber`
`protected StructuredQName`	`variableQName`

Constructor Summary

Constructors
Constructor and Description

LocalParam()

Constructors
Constructor and Description
`LocalParam()`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addReference(VariableReference ref, boolean isLoopingReference)` Register a variable reference that refers to the variable bound in this expression
`void`	`checkAgainstRequiredType(ExpressionVisitor visitor)` Check the select expression against the required type.
`int`	`computeCardinality()` Get the cardinality of the sequence returned by evaluating this instruction
`void`	`computeEvaluationMode()`
`int`	`computeSpecialProperties()` Get the static properties of this expression (other than its type).
`LocalParam`	`copy(RebindingMap rebindings)` Copy an expression.
`Sequence<?>`	`evaluateVariable(XPathContext c)` Evaluate the variable
`void`	`export(ExpressionPresenter out)` Diagnostic print of expression structure.
`int`	`getCardinality()` Get the cardinality of the result of this instruction.
`Expression`	`getConversion()` Get the conversion expression
`int`	`getConversionEvaluationMode()`
`java.lang.String`	`getExpressionName()` Get a name identifying the kind of expression, in terms meaningful to a user.
`int`	`getInstructionNameCode()` Get the name of this instruction for diagnostic and tracing purposes
`IntegerValue[]`	`getIntegerBoundsForVariable()` If the variable is bound to an integer, get the minimum and maximum possible values.
`ItemType`	`getItemType()` Get the item type of the items returned by evaluating this instruction
`int`	`getLocalSlotNumber()` If this is a local variable held on the local stack frame, return the corresponding slot number.
`SequenceType`	`getRequiredType()` Get the required type of this variable
`Expression`	`getSelectExpression()` Get the expression to which this variable is bound
`Sequence<?>`	`getSelectValue(XPathContext context)` Evaluate the variable.
`int`	`getSlotNumber()` Get the slot number allocated to this variable
`StructuredQName`	`getVariableQName()` Get the name of this variable
`boolean`	`hasVariableBinding(Binding binding)` Ask whether this expression is, or contains, the binding of a given variable
`boolean`	`isAssignable()` Test whether it is permitted to assign to the variable using the saxon:assign extension element.
`boolean`	`isCompatible(LocalParam other)` Check if parameter is compatible with another
`boolean`	`isGlobal()` Indicate whether the binding is local or global.
`boolean`	`isImplicitlyRequiredParam()` Ask whether this variable represents a parameter that is implicitly required, because there is no usable default value
`boolean`	`isIndexedVariable()` Ask whether the binding is to be indexed
`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
`boolean`	`isRequiredParam()` Ask whether this variable represents a required parameter
`boolean`	`isTunnelParam()` Ask whether this variable represents a tunnel parameter
`boolean`	`mayCreateNewNodes()` Determine whether this instruction creates new nodes.
`java.lang.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)
`Expression`	`optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType)` Perform optimisation of an expression and its subexpressions.
`TailCall`	`processLeavingTail(XPathContext context)` Process the local parameter declaration
`void`	`setConversion(Expression convertor)` Define a conversion that is to be applied to the supplied parameter value.
`void`	`setImplicitlyRequiredParam(boolean requiredParam)` Indicate that this variable represents a parameter that is implicitly required (because there is no usable default value)
`void`	`setIndexedVariable()` Say that the bound value has the potential to be indexed
`void`	`setReferenceCount(int refCount)` Set the nominal number of references to this variable
`void`	`setRequiredParam(boolean requiredParam)` Indicate that this variable represents a required parameter
`void`	`setRequiredType(SequenceType required)` Set the required type of this variable
`void`	`setSelectExpression(Expression select)` Set the expression to which this variable is bound
`void`	`setSlotNumber(int s)` Set the slot number of this variable
`void`	`setTunnel(boolean tunnel)` Indicate whether this variable represents a tunnel parameter
`void`	`setVariableQName(StructuredQName s)` Set the name of the variable
`java.lang.String`	`toShortString()` Produce a short string identifying the expression for use in error messages
`Expression`	`typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType)` Perform type checking of an expression and its subexpressions.

Methods inherited from class net.sf.saxon.expr.instruct.Instruction
alwaysCreatesNewNodes, assembleParams, assembleTunnelParams, dynamicError, evaluateAsString, evaluateItem, getConstructType, getImplementationMethod, getNetCost, getSourceLocator, isInstruction, isXSLT, iterate, process, someOperandCreatesNewNodes

Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeHashCode, computeStaticProperties, dynamicError, effectiveBooleanValue, equals, evaluatePendingUpdates, explain, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, hasCompatibleStaticContext, hashCode, hasSpecialProperty, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toString, typeCheckChildren, typeError, unordered, verifyParentPointers

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - variableQName
```
protected StructuredQName variableQName
```
  - slotNumber
```
protected int slotNumber
```
  - referenceCount
```
protected int referenceCount
```
  - evaluator
```
protected Evaluator evaluator
```
- Constructor Detail
  - LocalParam
```
public LocalParam()
```
- Method Detail
  - 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 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
  - 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)
  - optimize
```
public Expression optimize(ExpressionVisitor visitor,
                           ContextItemStaticInfo 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)
  - 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
  - getSelectValue
```
public Sequence<?> 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 - if evaluation of the select expression fails with a dynamic error
  - 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
  - getConversionEvaluationMode
```
public int getConversionEvaluationMode()
```
  - 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 java.lang.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
  - processLeavingTail
```
public TailCall processLeavingTail(XPathContext context)
                            throws XPathException
```
    Process the local parameter declaration
    
    Specified by:
    
    processLeavingTail in interface TailCallReturner
    
    Specified by:
    
    processLeavingTail in class Instruction
    
    Parameters:
    
    context - the dynamic context
    
    Returns:
    
    either null if processing is complete, or a tailcall if one is left outstanding
    
    Throws:
    
    XPathException - if a dynamic error occurs in the evaluation
  - 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
```
public int computeCardinality()
```
    Get the cardinality of the sequence returned by evaluating this instruction
    
    Overrides:
    
    computeCardinality in class Instruction
    
    Returns:
    
    the static cardinality
  - computeSpecialProperties
```
public 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 java.lang.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 java.lang.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

Class LocalParam

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression

Constructor Summary

Method Summary

Methods inherited from class net.sf.saxon.expr.instruct.Instruction

Methods inherited from class net.sf.saxon.expr.Expression

Methods inherited from class java.lang.Object

Field Detail

variableQName

slotNumber

referenceCount

evaluator

Constructor Detail

LocalParam

Method Detail

setSelectExpression

getSelectExpression

setRequiredType

getRequiredType

setRequiredParam

setImplicitlyRequiredParam

setTunnel

setReferenceCount

getCardinality

isAssignable

isGlobal

getLocalSlotNumber

isRequiredParam

isImplicitlyRequiredParam

isTunnelParam

typeCheck

optimize

computeEvaluationMode

copy

addReference

checkAgainstRequiredType

getSelectValue

getSlotNumber

setSlotNumber

setVariableQName

getVariableQName

setConversion

getConversion

getConversionEvaluationMode

getInstructionNameCode

operands

processLeavingTail

getIntegerBoundsForVariable

evaluateVariable

isCompatible

isLiftable

hasVariableBinding

getItemType

computeCardinality

computeSpecialProperties

mayCreateNewNodes

getExpressionName

toShortString

export

setIndexedVariable

isIndexedVariable