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Summary: Nested | Field | Method | Constr | Detail: Nested | Field | Method | Constr |
java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.VariableReference
Field Summary | |
protected Binding | |
protected SequenceType |
Fields inherited from class net.sf.saxon.expr.Expression | |
EVALUATE_METHOD , ITERATE_METHOD , PROCESS_METHOD , locationId , staticProperties |
Constructor Summary | |
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Method Summary | |
PathMap.PathMapNodeSet |
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int |
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int |
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Expression |
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boolean |
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Item |
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ValueRepresentation |
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void |
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void | |
Binding |
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String |
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int |
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int |
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ItemType |
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int |
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boolean |
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boolean |
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boolean |
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SequenceIterator |
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Expression |
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void |
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Expression |
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void |
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void |
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void |
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void |
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void |
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String |
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Expression |
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public VariableReference()
Create a Variable Reference
public VariableReference(Binding binding)
Create a Variable Reference
- Parameters:
binding
- the variable binding to which this variable refers
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 interface Expression
- Parameters:
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
- the PathMapNodeSet to which the paths embodied in this expression should be added
- Returns:
- the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this 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.
public int computeCardinality()
Get the static cardinality
- Overrides:
- computeCardinality in interface Expression
public int computeSpecialProperties()
Determine the special properties of this expression
- Overrides:
- computeSpecialProperties in interface Expression
- Returns:
StaticProperty.NON_CREATIVE
(unless the variable is assignable using saxon:assign)
public Expression copy()
Create a clone copy of this VariableReference
- Overrides:
- copy in interface Expression
- Returns:
- the cloned copy
public boolean equals(Object other)
Test if this expression is the same as another expression. (Note, we only compare expressions that have the same static and dynamic context).
public Item evaluateItem(XPathContext c) 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 interface Expression
- Parameters:
- 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
public ValueRepresentation evaluateVariable(XPathContext c) throws XPathException
Evaluate this variable
- Parameters:
c
- the XPath dynamic context
- Returns:
- the value of the variable
- Throws:
XPathException
- if any error occurs
public void explain(ExpressionPresenter destination)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
- Overrides:
- explain in interface Expression
public void fixup(Binding binding)
Fix up this variable reference to a Binding object, which enables the value of the variable to be located at run-time.
- Specified by:
- fixup in interface BindingReference
public Binding getBinding()
Get the object bound to the variable
- Returns:
- the Binding which declares this variable and associates it with a value
public String getDisplayName()
Get the display name of the variable. This is taken from the variable binding if possible
- Returns:
- the display name (a lexical QName
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 all three methods natively.
- Overrides:
- getImplementationMethod in interface Expression
public int getIntrinsicDependencies()
Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".
- Overrides:
- getIntrinsicDependencies in interface Expression
- Returns:
- a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression, if possible
- Overrides:
- getItemType in interface Expression
- Parameters:
th
- the type hierarchy cache
- Returns:
- the type of the variable, if this can be determined statically; otherwise Type.ITEM (meaning not known in advance)
public int hashCode()
get HashCode for comparing two expressions
public boolean isFiltered()
Determine whether this variable reference is filtered
- Returns:
- true if the value of the variable is filtered by a predicate
public boolean isFlattened()
Test whether this variable reference is flattened - that is, whether it is atomized etc
- Returns:
- true if the value of the variable is atomized, or converted to a string or number
public boolean isInLoop()
Determine whether this variable reference appears in a loop relative to its declaration. By default, when in doubt, returns true. This is calculated during type-checking.
- Returns:
- true if this variable reference occurs in a loop, where the variable declaration is outside the loop
public SequenceIterator iterate(XPathContext c) throws XPathException
Get the value of this variable in a given context.
- Specified by:
- iterate in interface SequenceIterable
- Overrides:
- iterate in interface Expression
- Parameters:
c
- the XPathContext which contains the relevant variable bindings
- Returns:
- the value of the variable, if it is defined
- Throws:
XPathException
- if the variable is undefined
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
Type-check the expression. At this stage details of the static type must be known. If the variable has a compile-time value, this is substituted for the variable reference
- Overrides:
- optimize in interface Expression
public void process(XPathContext c) throws XPathException
Process the instruction, without returning any tail calls
- Overrides:
- process in interface Expression
- Parameters:
public Expression promote(PromotionOffer offer) throws XPathException
Promote this expression if possible
- Overrides:
- promote in interface Expression
public void refineVariableReference(Expression parent)
Replace this VariableReference where appropriate by a more efficient implementation. This can only be done after all slot numbers are allocated. The efficiency is gained by binding the VariableReference directly to a local or global slot, rather than going via the Binding object
- Parameters:
parent
- the parent expression of this variable reference
public void refineVariableType(ItemType type, int cardinality, Value constantValue, int properties, ExpressionVisitor visitor)
public void setFiltered(boolean filtered)
Mark an expression as filtered: that is, it appears as the base expression in a filter expression. This notification currently has no effect except when the expression is a variable reference.
- Overrides:
- setFiltered in interface Expression
public void setFlattened(boolean flattened)
Mark an expression as being "flattened". This is a collective term that includes extracting the string value or typed value, or operations such as simple value construction that concatenate text nodes before atomizing. The implication of all of these is that although the expression might return nodes, the identity of the nodes has no significance. This is called during type checking of the parent expression. At present, only variable references take any notice of this notification.
- Overrides:
- setFlattened in interface Expression
public void setStaticType(SequenceType type, Value value, int properties)
Set static type. This is a callback from the variable declaration object. As well as supplying the static type, it may also supply a compile-time value for the variable. As well as the type information, other static properties of the value are supplied: for example, whether the value is an ordered node-set.
- Specified by:
- setStaticType in interface BindingReference
- Parameters:
type
- the static type of the variablevalue
- the value of the variable if this is a compile-time constantproperties
- static properties of the expression to which the variable is bound
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 interface Expression
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
Type-check the expression. At this stage details of the static type must be known. If the variable has a compile-time value, this is substituted for the variable reference
- Overrides:
- typeCheck in interface Expression