net.sf.saxon.expr

Class IfExpression

public class IfExpression extends ComputedExpression implements TailCallReturner

An IfExpression returns the value of either the "then" part or the "else" part, depending on the value of the condition

Constructor Summary
	IfExpression(Expression condition, Expression thenExp, Expression elseExp) Constructor

Method Summary
void	checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type.
int	computeCardinality() Determine the static cardinality of the result
int	computeSpecialProperties() Get the static properties of this expression (other than its type).
void	display(int level, NamePool pool, PrintStream out) Diagnostic print of expression structure
Item	evaluateItem(XPathContext context) Evaluate the conditional expression in a given context
Expression	getCondition()
Expression	getElseExpression()
ItemType	getItemType(TypeHierarchy th) Get data type of items in sequence returned by expression
Expression	getThenExpression()
SequenceIterator	iterate(XPathContext context) Iterate the path-expression in a given context
Iterator	iterateSubExpressions() Get the immediate subexpressions of this expression
boolean	markTailFunctionCalls() Mark tail calls on used-defined functions.
Expression	optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
void	process(XPathContext context) Process this expression as an instruction, writing results to the current receiver
TailCall	processLeavingTail(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.
Expression	promote(PromotionOffer offer) Promote this expression if possible
void	setCondition(Expression exp)
void	setThenExpression(Expression exp)
Expression	simplify(StaticContext env) Simplify an expression
void	suppressValidation(int validationMode) Suppress validation on contained element constructors, on the grounds that the parent element is already performing validation.
Expression	typeCheck(StaticContext env, ItemType contextItemType) Type-check the expression

Constructor Detail

IfExpression

public IfExpression(Expression condition, Expression thenExp, Expression elseExp)

Constructor

Method Detail

checkPermittedContents

public void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole)

Check that any elements and attributes constructed or returned by this expression are acceptable in the content model of a given complex type. It's always OK to say yes, since the check will be repeated at run-time. The process of checking element and attribute constructors against the content model of a complex type also registers the type of content expected of those constructors, so the static validation can continue recursively.

computeCardinality

public int computeCardinality()

Determine the static cardinality of the result

computeSpecialProperties

public int computeSpecialProperties()

Get the static properties of this expression (other than its type). The result is bit-signficant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.

display

public void display(int level, NamePool pool, PrintStream out)

Diagnostic print of expression structure

evaluateItem

public Item evaluateItem(XPathContext context)

Evaluate the conditional expression in a given context

Parameters: context the evaluation context

getCondition

public Expression getCondition()

getElseExpression

public Expression getElseExpression()

getItemType

public ItemType getItemType(TypeHierarchy th)

Get data type of items in sequence returned by expression

Parameters: th

getThenExpression

public Expression getThenExpression()

iterate

public SequenceIterator iterate(XPathContext context)

Iterate the path-expression in a given context

Parameters: context the evaluation context

iterateSubExpressions

public Iterator iterateSubExpressions()

Get the immediate subexpressions of this expression

markTailFunctionCalls

public boolean markTailFunctionCalls()

Mark tail calls on used-defined functions. For most expressions, this does nothing.

optimize

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

process

public void process(XPathContext context)

Process this expression as an instruction, writing results to the current receiver

processLeavingTail

public TailCall processLeavingTail(XPathContext context)

ProcessLeavingTail: called to do the real work of this instruction. This method must be implemented in each subclass. The results of the instruction are written to the current Receiver, which can be obtained via the Controller.

Parameters: context The dynamic context of the transformation, giving access to the current node, the current variables, etc.

Returns: null if the instruction has completed execution; or a TailCall indicating a function call or template call that is delegated to the caller, to be made after the stack has been unwound so as to save stack space.