net.sf.saxon.expr

Class BinaryExpression

public abstract class BinaryExpression extends ComputedExpression

Binary Expression: a numeric or boolean expression consisting of the two operands and an operator
Field Summary
protected Expressionoperand0
protected Expressionoperand1
protected intoperator
Constructor Summary
BinaryExpression(Expression p0, int op, Expression p1)
Create a binary expression identifying the two operands and the operator
Method Summary
intcomputeCardinality()
Determine the static cardinality.
intcomputeSpecialProperties()
Determine the special properties of this expression
voiddisplay(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure
protected StringdisplayOperator()
booleanequals(Object other)
Is this expression the same as another expression?
Expression[]getOperands()
Get the operands
intgetOperator()
Get the operator
inthashCode()
Get a hashCode for comparing two expressions.
protected static booleanisAssociative(int operator)
Determine whether an operator is associative, that is, ((a^b)^c) = (a^(b^c))
protected static booleanisCommutative(int operator)
Determine whether a binary operator is commutative, that is, A op B = B op A.
protected static booleanisInverse(int op1, int op2)
Test if one operator is the inverse of another, so that (A op1 B) is equivalent to (B op2 A).
IteratoriterateSubExpressions()
Get the immediate subexpressions of this expression
Expressionoptimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expressionpromote(PromotionOffer offer)
Promote this expression if possible
Expressionsimplify(StaticContext env)
Simplify an expression
ExpressiontypeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression.

Field Detail

operand0

protected Expression operand0

operand1

protected Expression operand1

operator

protected int operator

Constructor Detail

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 Detail

computeCardinality

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

computeSpecialProperties

public int computeSpecialProperties()
Determine the special properties of this expression

Returns: NON_CREATIVE. This is overridden for some subclasses.

display

public void display(int level, NamePool pool, PrintStream out)
Diagnostic print of expression structure

displayOperator

protected String displayOperator()

equals

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

getOperands

public Expression[] getOperands()
Get the operands

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))

isCommutative

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

Parameters: operator

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

optimize

public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
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.

Parameters: opt the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances. env the static context of the expression 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 ITEM_TYPE

Returns: the original expression, rewritten if appropriate to optimize execution

Throws: net.sf.saxon.trans.StaticError if an error is discovered during this phase (typically a type error)

promote

public Expression promote(PromotionOffer offer)
Promote this expression if possible

simplify

public Expression simplify(StaticContext env)
Simplify an expression

Returns: the simplified expression

typeCheck

public Expression typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression. Default implementation for binary operators that accept any kind of operand