Literal

java.lang.Object
- net.sf.saxon.expr.Expression
- - net.sf.saxon.expr.Literal

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, Locator

Direct Known Subclasses:

FunctionLiteral, StringLiteral
```
public class Literal
extends Expression
```
A Literal is an expression whose value is constant: it is a class that implements the Expression interface as a wrapper around a GroundedValue. This may derive from an actual literal in an XPath expression or query, or it may be the result of evaluating a constant subexpression such as true() or xs:date('2007-01-16')

See Also:
Serialized Form

Field Summary
- Fields inherited from class net.sf.saxon.expr.Expression
  EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, INHERITED_CONTEXT, INSPECTION_CONTEXT, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, NAVIGATION_CONTEXT, NODE_VALUE_CONTEXT, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, W3C_CONSUMING, W3C_FREE_RANGING, W3C_GROUP_CONSUMING, W3C_MOTIONLESS, WATCH_METHOD

Constructor Summary

Constructors
Modifier Constructor and Description

protected Literal(GroundedValue value)
Create a literal as a wrapper around a Value

Constructors
Modifier	Constructor and Description
`protected`	`Literal(GroundedValue value)` Create a literal as a wrapper around a Value

Method Summary

Methods
Modifier and Type	Method and Description
`PathMap.PathMapNodeSet`	`addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)` Add a representation of this expression to a PathMap.
`int`	`computeCardinality()` Determine the cardinality
`int`	`computeSpecialProperties()` Compute the static properties of this expression (other than its type).
`Expression`	`copy()` Copy an expression.
`boolean`	`effectiveBooleanValue(XPathContext context)` Get the effective boolean value of the expression.
`boolean`	`equals(Object obj)` Determine whether two literals are equal, when considered as expressions.
`CharSequence`	`evaluateAsString(XPathContext context)` Evaluate an expression as a String.
`Item`	`evaluateItem(XPathContext context)` Evaluate as a singleton item (or empty sequence).
`void`	`evaluatePendingUpdates(XPathContext context, PendingUpdateList pul)` Evaluate an updating expression, adding the results to a Pending Update List.
`void`	`explain(ExpressionPresenter out)` Diagnostic print of expression structure.
`int`	`getDependencies()` Determine which aspects of the context the expression depends on.
`ExpressionCompiler`	`getExpressionCompiler()` Return the compiler of the Literal expression
`IntegerValue[]`	`getIntegerBounds()` For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis.
`ItemType`	`getItemType(TypeHierarchy th)` Determine the data type of the items in the expression, if possible
`int`	`getStreamability(int syntacticContext, boolean allowExtensions, List<String> reasons)` Get the "sweep" of this expression as defined in the W3C streamability specifications.
`GroundedValue`	`getValue()` Get the value represented by this Literal
`int`	`hashCode()` Return a hash code to support the equals() function
`static boolean`	`isAtomic(Expression exp)` Test whether the literal wraps an atomic value.
`static boolean`	`isConstantBoolean(Expression exp, boolean value)` Test if a literal represents the boolean value true
`static boolean`	`isConstantOne(Expression exp)` Test if a literal represents the integer value 1
`static boolean`	`isEmptySequence(Expression exp)` Test whether the literal explicitly wraps an empty sequence.
`boolean`	`isSubtreeExpression()` Determine whether the expression can be evaluated without reference to the part of the context document outside the subtree rooted at the context node.
`boolean`	`isVacuousExpression()` Determine whether this is a vacuous expression as defined in the XQuery update specification
`SequenceIterator<? extends Item>`	`iterate()` Return an Iterator to iterate over the values of a sequence.
`SequenceIterator<? extends Item>`	`iterate(XPathContext context)` Return an Iterator to iterate over the values of a sequence.
`static Literal`	`makeEmptySequence()` Factory method to make an empty-sequence literal
`static Literal`	`makeLiteral(GroundedValue value)` Factory method to create a literal as a wrapper around a Value (factory method)
`Expression`	`optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` Optimize an expression
`void`	`process(XPathContext context)` Process the value as an instruction, without returning any tail calls
`Expression`	`simplify(ExpressionVisitor visitor)` Simplify an expression
`Pattern`	`toPattern(Configuration config, boolean is30)` Convert this expression to an equivalent XSLT pattern
`Pattern`	`toStreamingPattern(Configuration config, List<String> reasonForFailure)` Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)
`String`	`toString()` The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
`Expression`	`typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)` TypeCheck an expression

Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamingAdjunct, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, iterateSubExpressionInfo, iterateSubExpressions, markTailFunctionCalls, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

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

- Constructor Detail
  - Literal
```
protected Literal(GroundedValue value)
```
    Create a literal as a wrapper around a Value
    
    Parameters:
    value - the value of this literal
- Method Detail
  - getValue
```
public GroundedValue getValue()
```
    Get the value represented by this Literal
    
    Returns:
    the constant value
  - simplify
```
public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException
```
    Simplify an expression
    
    Overrides:
    
    simplify in class Expression
    
    Parameters:
    visitor - an expression visitor
    
    Returns:
    for a Value, this always returns the value unchanged
    
    Throws:
    
    XPathException - if an error is discovered during expression rewriting
  - typeCheck
```
public Expression typeCheck(ExpressionVisitor visitor,
                   ExpressionVisitor.ContextItemType contextItemType)
                     throws XPathException
```
    TypeCheck an 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:
    for a Value, this always returns the value unchanged
    
    Throws:
    
    XPathException - if an error is discovered during this phase (typically a type error)
  - optimize
```
public Expression optimize(ExpressionVisitor visitor,
                  ExpressionVisitor.ContextItemType contextItemType)
                    throws XPathException
```
    Optimize an expression
    
    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:
    for a Value, this always returns the value unchanged
    
    Throws:
    
    XPathException - if an error is discovered during this phase (typically a type error)
  - getItemType
```
public ItemType getItemType(TypeHierarchy th)
```
    Determine the data type of the items in the expression, if possible
    
    Specified by:
    
    getItemType in class Expression
    
    Parameters:
    th - The TypeHierarchy. Can be null if the target is an AtomicValue.
    
    Returns:
    for the default implementation: AnyItemType (not known)
  - computeCardinality
```
public int computeCardinality()
```
    Determine the cardinality
    
    Specified by:
    
    computeCardinality in class Expression
    
    Returns:
    the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE
  - computeSpecialProperties
```
public int computeSpecialProperties()
```
    Compute the static properties of this expression (other than its type). For a Value, the only special property is StaticProperty.NON_CREATIVE.
    
    Overrides:
    
    computeSpecialProperties in class Expression
    
    Returns:
    the value StaticProperty.NON_CREATIVE
  - getIntegerBounds
```
public IntegerValue[] getIntegerBounds()
```
    For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis. The default implementation returns null, meaning "unknown" or "not applicable". Other implementations return an array of two IntegerValue objects, representing the lower and upper bounds respectively. The values UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH are used to indicate values limited by the size of a string or the size of a sequence.
    
    Overrides:
    
    getIntegerBounds in class Expression
    
    Returns:
    the lower and upper bounds of integer values in the result, or null to indicate unknown or not applicable.
  - isVacuousExpression
```
public boolean isVacuousExpression()
```
    Determine whether this is a vacuous expression as defined in the XQuery update specification
    
    Overrides:
    
    isVacuousExpression in class Expression
    
    Returns:
    true if this expression is vacuous
  - 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
  - toPattern
```
public Pattern toPattern(Configuration config,
                boolean is30)
                  throws XPathException
```
    Convert this expression to an equivalent XSLT pattern
    
    Overrides:
    
    toPattern in class Expression
    
    Parameters:
    config - the Saxon configuration
    is30 - true if this is XSLT 3.0
    
    Returns:
    the equivalent pattern
    
    Throws:
    
    XPathException - if conversion is not possible
  - 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.
    
    Overrides:
    
    addToPathMap in class Expression
    
    Parameters:
    pathMap - the PathMap to which the expression should be added
    pathMapNodeSet - the set of nodes within the path map
    
    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
  - getDependencies
```
public final int getDependencies()
```
    Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as StaticProperty.VARIABLES and StaticProperty.CURRENT_NODE
    
    Overrides:
    
    getDependencies in class Expression
    
    Returns:
    for a Value, this always returns zero.
  - iterate
```
public SequenceIterator<? extends Item> 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 handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.
    
    Overrides:
    
    iterate in class Expression
    
    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
  - iterate
```
public SequenceIterator<? extends Item> iterate()
                                         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 handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.
    
    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
  - evaluateItem
```
public Item evaluateItem(XPathContext context)
                  throws XPathException
```
    Evaluate as a singleton item (or empty sequence). Note: this implementation returns the first item in the sequence. The method should not be used unless appropriate type-checking has been done to ensure that the value will be a singleton.
    
    Overrides:
    
    evaluateItem in class Expression
    
    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
  - process
```
public void process(XPathContext context)
             throws XPathException
```
    Process the value as an instruction, without returning any tail calls
    
    Overrides:
    
    process in class Expression
    
    Parameters:
    context - The dynamic context, giving access to the current node, the current variables, etc.
    
    Throws:
    
    XPathException - if a dynamic error occurs
  - evaluateAsString
```
public CharSequence evaluateAsString(XPathContext context)
                              throws XPathException
```
    Description copied from class: Expression
    
    Evaluate an expression as a String. This function must only be called in contexts where it is known that the expression will return a single string (or where an empty sequence is to be treated as a zero-length string). Implementations should not attempt to convert the result to a string, other than converting () to "". This method is used mainly to evaluate expressions produced by compiling an attribute value template.
    
    Overrides:
    
    evaluateAsString in class Expression
    
    Parameters:
    context - The context in which the expression is to be evaluated
    
    Returns:
    the value of the expression, evaluated in the current context. The expression must return a string or (); if the value of the expression is (), this method returns "".
    
    Throws:
    
    XPathException - if any dynamic error occurs evaluating the expression
  - effectiveBooleanValue
```
public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException
```
    Get the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.
    
    Overrides:
    
    effectiveBooleanValue in class Expression
    
    Parameters:
    context - The context in which the expression is to be evaluated
    
    Returns:
    the effective boolean value
    
    Throws:
    
    XPathException - if any dynamic error occurs evaluating the expression
  - evaluatePendingUpdates
```
public void evaluatePendingUpdates(XPathContext context,
                          PendingUpdateList pul)
                            throws XPathException
```
    Evaluate an updating expression, adding the results to a Pending Update List. The default implementation of this method, which is used for non-updating expressions, throws an UnsupportedOperationException. The implementation for a literal representing an empty sequence, however, is a no-op.
    
    Overrides:
    
    evaluatePendingUpdates in class Expression
    
    Parameters:
    context - the XPath dynamic evaluation context
    pul - the pending update list to which the results should be written
    
    Throws:
    
    XPathException - if evaluation fails
  - equals
```
public boolean equals(Object obj)
```
    Determine whether two literals are equal, when considered as expressions.
    
    Overrides:
    
    equals in class Object
    
    Parameters:
    obj - the other expression
    
    Returns:
    true if the two literals are equal. The test here requires (a) identity in the sense defined by XML Schema (same value in the same value space), and (b) identical type annotations. For example the literal xs:int(3) is not equal (as an expression) to xs:short(3), because the two expressions are not interchangeable.
  - hashCode
```
public int hashCode()
```
    Return a hash code to support the equals() function
    
    Overrides:
    
    hashCode in class Object
  - toString
```
public String toString()
```
    The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax
    
    Overrides:
    
    toString in class Expression
    
    Returns:
    a representation of the expression as a string
  - 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
  - isAtomic
```
public static boolean isAtomic(Expression exp)
```
    Test whether the literal wraps an atomic value. (Note, if this method returns false, this still leaves the possibility that the literal wraps a sequence that happens to contain a single atomic value).
    
    Parameters:
    exp - an expression
    
    Returns:
    true if the expression is a literal and the literal wraps an AtomicValue
  - isEmptySequence
```
public static boolean isEmptySequence(Expression exp)
```
    Test whether the literal explicitly wraps an empty sequence. (Note, if this method returns false, this still leaves the possibility that the literal wraps a sequence that happens to be empty).
    
    Parameters:
    exp - an expression
    
    Returns:
    true if the expression is a literal and the value of the literal is an empty sequence
  - isConstantBoolean
```
public static boolean isConstantBoolean(Expression exp,
                        boolean value)
```
    Test if a literal represents the boolean value true
    
    Parameters:
    exp - an expression
    value - true or false
    
    Returns:
    true if the expression is a literal and the literal represents the boolean value given in the second argument
  - isConstantOne
```
public static boolean isConstantOne(Expression exp)
```
    Test if a literal represents the integer value 1
    
    Parameters:
    exp - an expression
    
    Returns:
    true if the expression is a literal and the literal represents the integer value 1
  - isSubtreeExpression
```
public boolean isSubtreeExpression()
```
    Determine whether the expression can be evaluated without reference to the part of the context document outside the subtree rooted at the context node.
    
    Overrides:
    
    isSubtreeExpression in class Expression
    
    Returns:
    true if the expression has no dependencies on the context node, or if the only dependencies on the context node are downward selections using the self, child, descendant, attribute, and namespace axes.
  - makeEmptySequence
```
public static Literal makeEmptySequence()
```
    Factory method to make an empty-sequence literal
    
    Returns:
    a literal whose value is the empty sequence
  - makeLiteral
```
public static Literal makeLiteral(GroundedValue value)
```
    Factory method to create a literal as a wrapper around a Value (factory method)
    
    Parameters:
    value - the value of this literal
    
    Returns:
    the Literal
  - toStreamingPattern
```
public Pattern toStreamingPattern(Configuration config,
                         List<String> reasonForFailure)
```
    Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)
    
    Overrides:
    
    toStreamingPattern in class Expression
    
    Parameters:
    config - the Saxon configuration
    reasonForFailure - a list which will be populated with messages giving reasons why the expression cannot be converted
    
    Returns:
    the equivalent pattern if conversion succeeds; otherwise null
  - getStreamability
```
public int getStreamability(int syntacticContext,
                   boolean allowExtensions,
                   List<String> reasons)
```
    Description copied from class: Expression
    
    Get the "sweep" of this expression as defined in the W3C streamability specifications. This provides an assessment of stylesheet code against the W3C criteria for guaranteed streamability, and is implemented to allow these criteria to be tested. It is not the case that all expression that emerge as streamable from this analysis are currently capable of being streamed by Saxon
    
    Overrides:
    
    getStreamability in class Expression
    
    Parameters:
    syntacticContext - one of the values Expression.NAVIGATION_CONTEXT, Expression.NODE_VALUE_CONTEXT, Expression.INHERITED_CONTEXT, Expression.INSPECTION_CONTEXT
    allowExtensions - if false, the definition of "guaranteed streamability" in the W3C specification is used. If true, Saxon extensions are permitted, which make some
    reasons - the caller may supply a list, in which case the implementation may add to this list a message explaining why the construct is not streamable, suitable for inclusion in an error message.
    
    Returns:
    one of the values Expression.W3C_MOTIONLESS, Expression.W3C_CONSUMING, Expression.W3C_GROUP_CONSUMING, Expression.W3C_FREE_RANGING
  - getExpressionCompiler
```
public ExpressionCompiler getExpressionCompiler()
```
    Return the compiler of the Literal expression
    
    Overrides:
    
    getExpressionCompiler in class Expression
    
    Returns:
    the relevant ExpressionCompiler

Class Literal

Field Summary

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

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Constructor Detail

Literal

Method Detail

getValue

simplify

typeCheck

optimize

getItemType

computeCardinality

computeSpecialProperties

getIntegerBounds

isVacuousExpression

copy

toPattern

addToPathMap

getDependencies

iterate

iterate

evaluateItem

process

evaluateAsString

effectiveBooleanValue

evaluatePendingUpdates

equals

hashCode

toString

explain

isAtomic

isEmptySequence

isConstantBoolean

isConstantOne

isSubtreeExpression

makeEmptySequence

makeLiteral

toStreamingPattern

getStreamability

getExpressionCompiler