Package net.sf.saxon.expr
Class IfExpression
java.lang.Object
net.sf.saxon.expr.ComputedExpression
net.sf.saxon.expr.IfExpression
- All Implemented Interfaces:
Serializable
,SourceLocator
,Container
,Expression
,TailCallReturner
,InstructionInfoProvider
An IfExpression returns the value of either the "then" part or the "else" part,
depending on the value of the condition
- See Also:
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Field Summary
Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
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Constructor Summary
ConstructorsConstructorDescriptionIfExpression
(Expression condition, Expression thenExp, Expression elseExp) Constructor -
Method Summary
Modifier and TypeMethodDescriptionvoid
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
Determine the static cardinality of the resultint
Get the static properties of this expression (other than its type).void
display
(int level, PrintStream out, Configuration config) Diagnostic print of expression structureevaluateItem
(XPathContext context) Evaluate the conditional expression in a given contextGet data type of items in sequence returned by expressioniterate
(XPathContext context) Iterate the path-expression in a given contextGet the immediate subexpressions of this expressionboolean
markTailFunctionCalls
(int nameCode, int arity) Mark tail calls on used-defined functions.optimize
(Optimizer opt, StaticContext env, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.void
process
(XPathContext context) Process this expression as an instruction, writing results to the current receiverprocessLeavingTail
(XPathContext context) ProcessLeavingTail: called to do the real work of this instruction.promote
(PromotionOffer offer) Promote this expression if possibleboolean
replaceSubExpression
(Expression original, Expression replacement) Replace one subexpression by a replacement subexpressionvoid
setCondition
(Expression exp) void
simplify
(StaticContext env) Simplify an expressionvoid
suppressValidation
(int validationMode) Suppress validation on contained element constructors, on the grounds that the parent element is already performing validation.typeCheck
(StaticContext env, ItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, typeError
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Constructor Details
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IfExpression
Constructor
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Method Details
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getCondition
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getThenExpression
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getElseExpression
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setCondition
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setThenExpression
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simplify
Simplify an expression- Specified by:
simplify
in interfaceExpression
- Overrides:
simplify
in classComputedExpression
- Parameters:
env
- the static context- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
Type-check the expression- Specified by:
typeCheck
in interfaceExpression
- Parameters:
env
- the static context of the expressioncontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
- Throws:
XPathException
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optimize
public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException Description copied from interface:Expression
Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.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.
- Specified by:
optimize
in interfaceExpression
- 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 expressioncontextItemType
- 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 toType.ITEM_TYPE
- Returns:
- the original expression, rewritten if appropriate to optimize execution
- Throws:
XPathException
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promote
Promote this expression if possible- Specified by:
promote
in interfaceExpression
- Overrides:
promote
in classComputedExpression
- Parameters:
offer
- details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression- Returns:
- if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
- Throws:
XPathException
- if any error is detected
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iterateSubExpressions
Get the immediate subexpressions of this expression- Specified by:
iterateSubExpressions
in interfaceExpression
- Overrides:
iterateSubExpressions
in classComputedExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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replaceSubExpression
Replace one subexpression by a replacement subexpression- Specified by:
replaceSubExpression
in interfaceContainer
- Overrides:
replaceSubExpression
in classComputedExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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suppressValidation
public void suppressValidation(int validationMode) Suppress validation on contained element constructors, on the grounds that the parent element is already performing validation. The default implementation does nothing.- Overrides:
suppressValidation
in classComputedExpression
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markTailFunctionCalls
public boolean markTailFunctionCalls(int nameCode, int arity) Mark tail calls on used-defined functions. For most expressions, this does nothing.- Overrides:
markTailFunctionCalls
in classComputedExpression
- Returns:
- true if a tail recursive call was found and if this call accounts for the whole of the value.
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checkPermittedContents
public void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) throws XPathException 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.- Specified by:
checkPermittedContents
in interfaceExpression
- Overrides:
checkPermittedContents
in classComputedExpression
- Parameters:
parentType
- The schema typeenv
- the static contextwhole
- true if this expression is expected to make the whole content of the type, false if it is expected to make up only a part- Throws:
XPathException
- if the expression doesn't match the required content type
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evaluateItem
Evaluate the conditional expression in a given context- Specified by:
evaluateItem
in interfaceExpression
- Overrides:
evaluateItem
in classComputedExpression
- Parameters:
context
- the evaluation context- Returns:
- the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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iterate
Iterate the path-expression in a given context- Specified by:
iterate
in interfaceExpression
- Overrides:
iterate
in classComputedExpression
- Parameters:
context
- the evaluation context- Returns:
- a SequenceIterator that can be used to iterate over the result of the expression
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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process
Process this expression as an instruction, writing results to the current receiver- Specified by:
process
in interfaceExpression
- Overrides:
process
in classComputedExpression
- Parameters:
context
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
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processLeavingTail
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.- Specified by:
processLeavingTail
in interfaceTailCallReturner
- 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.
- Throws:
XPathException
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getItemType
Get data type of items in sequence returned by expression- Specified by:
getItemType
in interfaceExpression
- Parameters:
th
-- Returns:
- a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)
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computeCardinality
public int computeCardinality()Determine the static cardinality of the result- Specified by:
computeCardinality
in classComputedExpression
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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.- Overrides:
computeSpecialProperties
in classComputedExpression
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display
Diagnostic print of expression structure- Specified by:
display
in interfaceExpression
- Parameters:
level
- indentation level for this expressionout
- Output destinationconfig
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