net.sf.saxon.expr

Class BooleanExpression

public class BooleanExpression extends BinaryExpression

Boolean expression: two truth values combined using AND or OR.
Constructor Summary
BooleanExpression(Expression p1, int operator, Expression p2)
Method Summary
intcomputeCardinality()
Determine the static cardinality.
booleaneffectiveBooleanValue(XPathContext c)
Evaluate as a boolean.
ItemevaluateItem(XPathContext context)
Evaluate the expression
ItemTypegetItemType(TypeHierarchy th)
Determine the data type of the expression
static voidlistAndComponents(Expression exp, List list)
Construct a list containing the "anded" subexpressions of an expression: if the expression is (A and B and C), this returns (A, B, C).
Expressionnegate(StaticContext env)
Return the negation of this boolean expression, that is, an expression that returns true when this expression returns false, and vice versa
Expressionoptimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.

Constructor Detail

BooleanExpression

public BooleanExpression(Expression p1, int operator, Expression p2)

Method Detail

computeCardinality

public int computeCardinality()
Determine the static cardinality. Returns [1..1]

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext c)
Evaluate as a boolean.

evaluateItem

public Item evaluateItem(XPathContext context)
Evaluate the expression

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression

Parameters: th

Returns: Type.BOOLEAN

listAndComponents

public static void listAndComponents(Expression exp, List list)
Construct a list containing the "anded" subexpressions of an expression: if the expression is (A and B and C), this returns (A, B, C).

Parameters: exp the expression to be decomposed list the list to which the subexpressions are to be added.

negate

public Expression negate(StaticContext env)
Return the negation of this boolean expression, that is, an expression that returns true when this expression returns false, and vice versa

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)