net.sf.saxon.functions
public class BooleanFn extends SystemFunction implements Negatable
Field Summary | |
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static int | BOOLEAN |
static int | FALSE |
static int | NOT |
static int | TRUE |
Method Summary | |
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void | checkArguments(ExpressionVisitor visitor)
Static analysis: prevent sorting of the argument |
boolean | effectiveBooleanValue(XPathContext c)
Evaluate the effective boolean value |
Item | evaluateItem(XPathContext context)
Evaluate the function |
boolean | isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatable
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Expression | negate()
Create an expression that returns the negation of this expression |
Expression | optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
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static Expression | rewriteEffectiveBooleanValue(Expression exp, ExpressionVisitor visitor, ItemType contextItemType)
Optimize an expression whose effective boolean value is required |
Expression | simplify(ExpressionVisitor visitor)
Simplify the function call. |
Returns: true if it is
Returns: the negated expression
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: 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 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)
Parameters: exp the expression whose EBV is to be evaluated visitor an expression visitor contextItemType the type of the context item for this expression
Returns: an expression that returns the EBV of exp, or null if no optimization was possible
Throws: XPathException if static errors are found
Parameters: visitor an expression visitor