net.sf.saxon.expr
public class BooleanExpression extends BinaryExpression
Constructor Summary | |
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BooleanExpression(Expression p1, int operator, Expression p2) |
Method Summary | |
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int | computeCardinality()
Determine the static cardinality. |
boolean | effectiveBooleanValue(XPathContext c)
Evaluate as a boolean. |
Item | evaluateItem(XPathContext context)
Evaluate the expression |
ItemType | getItemType(TypeHierarchy th)
Determine the data type of the expression |
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). |
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 |
Expression | optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
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Parameters: th
Returns: Type.BOOLEAN
Parameters: exp the expression to be decomposed list the list to which the subexpressions are to be added.
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)