net.sf.saxon.functions

Class BooleanFn

public class BooleanFn extends SystemFunction

This class supports the XPath functions boolean(), not(), true(), and false()
Field Summary
static intBOOLEAN
static intFALSE
static intNOT
static intTRUE
Method Summary
voidcheckArguments(StaticContext env)
Static analysis: prevent sorting of the argument
booleaneffectiveBooleanValue(XPathContext c)
Evaluate the effective boolean value
ItemevaluateItem(XPathContext context)
Evaluate the function
Expressionoptimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.
Expressionsimplify(StaticContext env)
Simplify the function call.

Field Detail

BOOLEAN

public static final int BOOLEAN

FALSE

public static final int FALSE

NOT

public static final int NOT

TRUE

public static final int TRUE

Method Detail

checkArguments

public void checkArguments(StaticContext env)
Static analysis: prevent sorting of the argument

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext c)
Evaluate the effective boolean value

evaluateItem

public Item evaluateItem(XPathContext context)
Evaluate the function

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)

simplify

public Expression simplify(StaticContext env)
Simplify the function call. Default method is to simplify each of the supplied arguments and evaluate the function if all are now known.