net.sf.saxon.expr

Class UnaryExpression

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator
Known Direct Subclasses:
AtomicSequenceConverter, Atomizer, CardinalityChecker, CastableExpression, CastExpression, DocumentSorter, FirstItemExpression, InstanceOfExpression, ItemChecker, LazyExpression, NegateExpression, NumericPromoter, SingletonAtomizer, TailCallLoop, UntypedAtomicConverter

public abstract class UnaryExpression
extends Expression

Unary Expression: an expression taking a single operand expression

Field Summary

protected Expression
operand

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

UnaryExpression(Expression p0)

Method Summary

int
computeCardinality()
Determine the static cardinality.
int
computeSpecialProperties()
Get the static properties of this expression (other than its type).
protected String
displayExpressionName()
Return the element name to use in the expression tree
protected String
displayOperator(Configuration config)
Give a string representation of the operator for use in diagnostics
boolean
equals(Object other)
Is this expression the same as another expression?
void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.
Expression
getBaseExpression()
ItemType
getItemType(TypeHierarchy th)
Determine the data type of the expression, if possible.
int
hashCode()
get HashCode for comparing two expressions.
Iterator
iterateSubExpressions()
Get the immediate subexpressions of this expression
Expression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expression
promote(PromotionOffer offer)
Promote this expression if possible
boolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression
Expression
simplify(ExpressionVisitor visitor)
Simplify an expression
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, ItemType contextItemType)
Type-check the expression.

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Field Details

operand

protected Expression operand

Constructor Details

UnaryExpression

public UnaryExpression(Expression p0)

Method Details

computeCardinality

public int computeCardinality()
Determine the static cardinality. Default implementation returns the cardinality of the operand
Overrides:
computeCardinality in interface Expression

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 interface Expression

displayExpressionName

protected String displayExpressionName()
Return the element name to use in the expression tree

displayOperator

protected String displayOperator(Configuration config)
Give a string representation of the operator for use in diagnostics
Parameters:
config -
Returns:
the operator, as a string

equals

public boolean equals(Object other)
Is this expression the same as another expression?

explain

public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
Overrides:
explain in interface Expression

getBaseExpression

public Expression getBaseExpression()

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression, if possible. The default implementation for unary expressions returns the item type of the operand
Overrides:
getItemType in interface Expression
Parameters:
th - the type hierarchy cache
Returns:
the item type of the items in the result sequence, insofar as this is known statically.

hashCode

public int hashCode()
get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.

iterateSubExpressions

public Iterator iterateSubExpressions()
Get the immediate subexpressions of this expression
Overrides:
iterateSubExpressions in interface Expression

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
            throws XPathException
Perform optimisation of an expression and its subexpressions.

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 interface 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)

promote

public Expression promote(PromotionOffer offer)
            throws XPathException
Promote this expression if possible
Overrides:
promote in interface Expression

replaceSubExpression

public boolean replaceSubExpression(Expression original,
                                    Expression replacement)
Replace one subexpression by a replacement subexpression
Overrides:
replaceSubExpression in interface Expression
Parameters:
original - the original subexpression
replacement - the replacement subexpression
Returns:
true if the original subexpression is found

simplify

public Expression simplify(ExpressionVisitor visitor)
            throws XPathException
Simplify an expression
Overrides:
simplify in interface Expression
Parameters:
visitor - an expression visitor
Returns:
the simplified expression

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 interface Expression

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
            throws XPathException
Type-check the expression. Default implementation for unary operators that accept any kind of operand
Overrides:
typeCheck in interface Expression