net.sf.saxon.expr

Class BinaryExpression

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator
Known Direct Subclasses:
ArithmeticExpression, ArithmeticExpression10, BooleanExpression, GeneralComparison, GeneralComparison10, IdentityComparison, RangeExpression, SingletonComparison, 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

protected Expression
operand0
protected Expression
operand1
protected int
operator

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Constructor Summary

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

Method Summary

int
computeCardinality()
Determine the static cardinality.
int
computeSpecialProperties()
Determine the special properties of this expression
protected String
displayOperator()
boolean
equals(Object other)
Is this expression the same as another expression?
void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.
Expression[]
getOperands()
Get the operands
int
getOperator()
Get the operator
int
hashCode()
Get a hashCode for comparing two expressions.
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).
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
void
setFlattened(boolean flattened)
Mark an expression as being "flattened".
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

operand0

protected Expression operand0

operand1

protected Expression operand1

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

computeCardinality

public int computeCardinality()
Determine the static cardinality. Default implementation returns [0..1] if either operand can be empty, or [1..1] otherwise.
Overrides:
computeCardinality in interface Expression

computeSpecialProperties

public int computeSpecialProperties()
Determine the special properties of this expression
Overrides:
computeSpecialProperties in interface Expression
Returns:
StaticProperty.NON_CREATIVE. This is overridden for some subclasses.

displayOperator

protected String displayOperator()

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

getOperands

public Expression[] getOperands()
Get the operands
Returns:
the two operands of the binary expression, as an array of length 2

getOperator

public int getOperator()
Get the operator

hashCode

public int hashCode()
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.

isAssociative

protected static boolean isAssociative(int operator)
Determine whether an operator is associative, that is, ((a^b)^c) = (a^(b^c))
Returns:
true if the operator is associative

isCommutative

protected static boolean isCommutative(int operator)
Determine whether a binary operator is commutative, that is, A op B = B op A.
Returns:
true if the operator is commutative

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

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

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

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 binary operators that accept any kind of operand
Overrides:
typeCheck in interface Expression