Package net.sf.saxon.expr

Class BinaryExpression

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.BinaryExpression

All Implemented Interfaces:

ExportAgent, Locatable, IdentityComparable, Traceable

Direct Known Subclasses:

ArithmeticExpression, BooleanExpression, FilterExpression, GeneralComparison, GeneralComparison10, IdentityComparison, LookupExpression, SlashExpression, SwitchCaseComparison, ValueComparison, VennExpression

public abstract class BinaryExpression
extends Expression

Binary Expression: a numeric or boolean expression consisting of the two operands and an operator

Field Summary

Fields

Modifier and Type	Field	Description
protected int	operator

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

Constructor Summary

Constructors

Constructor	Description
BinaryExpression(Expression p0, int op, Expression p1)	Create a binary expression identifying the two operands and the operator

Method Summary

Modifier and Type	Method	Description
protected int	computeCardinality()	Determine the static cardinality.
protected int	computeHashCode()	Get a hashCode for comparing two expressions.
protected int	computeSpecialProperties()	Determine the special properties of this expression
protected String	displayOperator()	Display the operator used by this binary expression
boolean	equals(Object other)	Is this expression the same as another expression?
protected void	explainExtraAttributes(ExpressionPresenter out)	Add subclass-specific attributes to the expression tree explanation.
void	export(ExpressionPresenter out)	Diagnostic print of expression structure.
int	getImplementationMethod()	An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
Operand	getLhs()	Get the left-hand operand
final Expression	getLhsExpression()	Get the left-hand operand expression
protected OperandRole	getOperandRole(int arg)	Get the operand role
int	getOperator()	Get the operator
Operand	getRhs()	Get the right-hand operand
final Expression	getRhsExpression()	Get the right-hand operand expression
protected static boolean	isAssociative(int operator)	Determine whether an operator is associative, that is, ((a^b)^c) = (a^(b^c))
protected static boolean	isCommutative(int operator)	Determine whether a binary operator is commutative, that is, A op B = B op A.
protected static boolean	isInverse(int op1, int op2)	Test if one operator is the inverse of another, so that (A op1 B) is equivalent to (B op2 A).
final Iterable<Operand>	operands()	Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType)	Perform optimisation of an expression and its subexpressions.
void	setFlattened(boolean flattened)	Mark an expression as being "flattened".
void	setLhsExpression(Expression child)	Set the left-hand operand expression
void	setRhsExpression(Expression child)	Set the right-hand operand expression
protected String	tag()	Get the element name used to identify this expression in exported expression format
String	toShortString()	Produce a short string identifying the expression for use in error messages
String	toString()	Represent the expression as a string.
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo)	Type-check the expression.

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

addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, copy, dispatchTailCall, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, getCardinality, getConfiguration, getCost, getDependencies, getElaborator, getEvaluationMethod, getExpressionName, getExtraProperty, getIntegerBounds, getIntrinsicDependencies, getItemType, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStaticUType, getStreamerName, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, makeElaborator, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, supportsLazyEvaluation, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers, withLocation

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface net.sf.saxon.trace.Traceable

gatherProperties

Field Details

operator

protected int operator

Constructor Details

BinaryExpression

public BinaryExpression(Expression p0,
 int op,
 Expression p1)

Create a binary expression identifying the two operands and the operator

Parameters:

p0 - the left-hand operand

op - the operator, as a token returned by the Tokenizer (e.g. Token.AND)

p1 - the right-hand operand

Method Details

operands

public final Iterable<Operand> operands()

Description copied from class: Expression

Get the immediate sub-expressions of this expression, with information about the relationship of each expression to its parent expression.

If the expression is a Callable, then it is required that the order of the operands returned by this function is the same as the order of arguments supplied to the corresponding call() method.

Overrides:

operands in class Expression

Returns:

an iterator containing the sub-expressions of this expression

getOperandRole

protected OperandRole getOperandRole(int arg)

Get the operand role

Parameters:

arg - which argument: 0 for the lhs, 1 for the rhs

Returns:

the operand role

getLhs

public Operand getLhs()

Get the left-hand operand

Returns:

the left-hand operand

getLhsExpression

public final Expression getLhsExpression()

Get the left-hand operand expression

Returns:

the left-hand operand child expression

setLhsExpression

public void setLhsExpression(Expression child)

Set the left-hand operand expression

Parameters:

child - the left-hand operand expression

getRhs

public Operand getRhs()

Get the right-hand operand

Returns:

the right-hand operand

getRhsExpression

public final Expression getRhsExpression()

Get the right-hand operand expression

Returns:

the right-hand operand expression

setRhsExpression

public void setRhsExpression(Expression child)

Set the right-hand operand expression

Parameters:

child - the right-hand operand expression

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
 ContextItemStaticInfo contextInfo)
                     throws XPathException

Type-check the expression. Default implementation for binary operators that accept any kind of operand

Overrides:

typeCheck in class Expression

Parameters:

visitor - an expression visitor

contextInfo - 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

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 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)

setFlattened

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.

Overrides:

setFlattened in class Expression

Parameters:

flattened - set to true if the result of the expression is atomized or otherwise turned into an atomic value

getOperator

public int getOperator()

Get the operator

Returns:

the operator, for example Token.PLUS

computeCardinality

protected int computeCardinality()

Determine the static cardinality. Default implementation returns [0..1] if either operand can be empty, or [1..1] otherwise, provided that the arguments are of atomic type. This caveat is necessary because the method can be called before type-checking, and a node or array with cardinality [1..n] might be atomized to an empty sequence.

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. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

computeSpecialProperties

protected int computeSpecialProperties()

Determine the special properties of this expression

Overrides:

computeSpecialProperties in class Expression

Returns:

StaticProperty.NO_NODES_NEWLY_CREATED. This is overridden for some subclasses.

isCommutative

protected static boolean isCommutative(int operator)

Determine whether a binary operator is commutative, that is, A op B = B op A.

Parameters:

operator - the operator, for example Token.PLUS

Returns:

true if the operator is commutative

isAssociative

protected static boolean isAssociative(int operator)

Determine whether an operator is associative, that is, ((a^b)^c) = (a^(b^c))

Parameters:

operator - the operator, for example Token.PLUS

Returns:

true if the operator is associative

isInverse

protected static boolean isInverse(int op1,
 int op2)

Test if one operator is the inverse of another, so that (A op1 B) is equivalent to (B op2 A). Commutative operators are the inverse of themselves and are therefore not listed here.

Parameters:

op1 - the first operator

op2 - the second operator

Returns:

true if the operators are the inverse of each other

getImplementationMethod

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 directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.

Specified by:

getImplementationMethod in class Expression

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

equals

public boolean equals(Object other)

Is this expression the same as another expression?

Overrides:

equals in class Expression

Parameters:

other - the other operand; the result is false if this is not an Expression

Returns:

true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.

computeHashCode

protected int computeHashCode()

Get a 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.

Overrides:

computeHashCode in class Expression

Returns:

a computed hash code

toString

public String toString()

Represent the expression as a string. The resulting string will be a valid XPath 3.0 expression with no dependencies on namespace bindings other than the binding of the prefix "xs" to the XML Schema namespace.

Overrides:

toString in class Expression

Returns:

the expression as a string in XPath 3.0 syntax

toShortString

public String toShortString()

Description copied from class: Expression

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 output destination for the displayed expression tree

Throws:

XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

tag

protected String tag()

Get the element name used to identify this expression in exported expression format

Returns:

the element name used to identify this expression

explainExtraAttributes

protected void explainExtraAttributes(ExpressionPresenter out)

Add subclass-specific attributes to the expression tree explanation. Default implementation does nothing; this is provided for subclasses to override.

Parameters:

out - the output destination for the displayed expression tree

displayOperator

protected String displayOperator()

Display the operator used by this binary expression

Returns:

String representation of the operator (for diagnostic display only)