com.saxonica.ee.expr

Class WhichOf

java.lang.Object

net.sf.saxon.expr.Expression

com.saxonica.ee.expr.WhichOf

All Implemented Interfaces:

IdentityComparable

public class WhichOf
extends Expression

WhichOf is an expression used internally during XSLT pattern matching. It contains a list of (typically boolean) expressions, numbered 0..n, and evaluating the WhichOf returns the integer index of the first of these expressions whose effective boolean value is true.

Currently used only in ModeExperimentalChoice which is not used by default.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	WhichOf.ChoiceExpression This inner class associates a choice with its index in the choice list and any necessary preconditions

Field Summary

Fields

Modifier and Type	Field and Description
List<WhichOf.ChoiceExpression>	choices

Fields inherited from class net.sf.saxon.expr.Expression

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
WhichOf(Expression[] conditions) Construct a whichOf instruction

Method Summary

Methods

Modifier and Type	Method and Description
protected int	computeCardinality() Compute the static cardinality of this expression
Expression	copy() Copy an expression.
Item	evaluateItem(XPathContext context) Evaluate an expression as a single item.
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
void	export(ExpressionPresenter out, List<Rule> rules)
Expression[]	getConditions()
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType	getItemType() Determine the data type of the expression, if possible.
HashMap<Expression,List<WhichOf.ChoiceExpression>>	getPreconditionGroups() Group the subexpressions that share the same preconditions
Iterable<Operand>	operands() Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)
Expression	simplify() Simplify an expression.
String	toString() The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
int	which(int start, int end, XPathContext context) Identify which of the choices to take
int	which(int start, XPathContext context) Identify which of the choices to take
int	which(XPathContext context) Identify which of the choices to take

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeSpecialProperties, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExpressionCompiler, getExpressionName, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getPosture, getPostureAndSweepIfKnown, getProperties, getProperty, getRetainedStaticContext, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStreamability, getStreamingAdjunct, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isCallOnSystemFunction, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, operandSparseList, optimize, optimizeChildren, optimizeForType, process, promote, promoteChildren, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setFiltered, setFlattened, setLocation, setParentExpression, setPostureAndSweep, setRetainedStaticContext, setRetainedStaticContextLocally, setStaticProperty, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, toShortString, toStreamingPattern, typeCheck, typeCheckChildren, typeError, unordered

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

choices

public List<WhichOf.ChoiceExpression> choices

Constructor Detail

WhichOf

public WhichOf(Expression[] conditions)

Construct a whichOf instruction

Parameters:

conditions - the conditions to be tested, in order

Method Detail

getItemType

public ItemType getItemType()

Description copied from class: Expression

Determine the data type of the expression, if possible. All expression return sequences, in general; this method determines the type of the items within the sequence, assuming that (a) this is known in advance, and (b) it is the same for all items in the sequence.

This method should always return a result, though it may be the best approximation that is available at the time.

Specified by:

getItemType in class Expression

Returns:

a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known at compile time)

getConditions

public Expression[] getConditions()

export

public void export(ExpressionPresenter out)

Description copied from class: Expression

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:

export in class Expression

Parameters:

out - the expression presenter used to display the structure

export

public void export(ExpressionPresenter out,
          List<Rule> rules)

getPreconditionGroups

public HashMap<Expression,List<WhichOf.ChoiceExpression>> getPreconditionGroups()

Group the subexpressions that share the same preconditions

Returns:

a map that groups the subexpressions according to the combined precondition that they share. Note that this involves equality comparison between expressions, which can be expensive (and is not 100% reliable, in the sense that that some equivalences between expressions are not recognized)

computeCardinality

protected int computeCardinality()

Description copied from class: Expression

Compute the static cardinality of this expression

Specified by:

computeCardinality in class Expression

Returns:

the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE

copy

public Expression copy()

Description copied from class: Expression

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Returns:

the copy of the original expression

toString

public String toString()

The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax

Overrides:

toString in class Expression

Returns:

a representation of the expression as a string

simplify

public Expression simplify()
                    throws XPathException

Simplify an expression. This performs any static optimization (by rewriting the expression as a different expression).

Overrides:

simplify in class Expression

Returns:

the simplified expression (or the original if unchanged, or if modified in-situ)

Throws:

XPathException - if an error is discovered during expression rewriting

operands

public Iterable<Operand> operands()

Get all the XPath expressions associated with this instruction (in XSLT terms, the expression present on attributes of the instruction, as distinct from the child instructions in a sequence construction)

Overrides:

operands in class Expression

Returns:

an iterator containing the sub-expressions of this expression

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate an expression as a single item. This always returns either a single Item or null (denoting the empty sequence). No conversion is done. This method should not be used unless the static type of the expression is a subtype of "item" or "item?": that is, it should not be called if the expression may return a sequence. There is no guarantee that this condition will be detected.

Overrides:

evaluateItem in class Expression

Parameters:

context - The context in which the expression is to be evaluated

Returns:

a numerical literal representing the case found, otherwise null if none matches.

Throws:

XPathException - if any dynamic error occurs evaluating the expression

getImplementationMethod

public int getImplementationMethod()

Description copied from class: Expression

An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.

Specified by:

getImplementationMethod in class Expression

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

which

public int which(XPathContext context)
          throws XPathException

Identify which of the choices to take

Parameters:

context - the dynamic context

Returns:

integer the index of the first choice that matches, zero-based; or -1 if none of the choices matches

Throws:

XPathException - if evaluating a condition fails

which

public int which(int start,
        XPathContext context)
          throws XPathException

Identify which of the choices to take

Parameters:

start - the starting index to use - supports next-match

context - the dynamic context

Returns:

integer the index of the first choice that matches, zero-based; or -1 if none of the choices matches

Throws:

XPathException - if evaluating a condition fails

which

public int which(int start,
        int end,
        XPathContext context)
          throws XPathException

Identify which of the choices to take

Parameters:

start - the starting index to use - supports apply-imports

end - the ending index to use (inclusive) - supports apply-imports

context - the dynamic context

Returns:

integer the index of the first choice that matches, zero-based; or -1 if none of the choices matches

Throws:

XPathException - if evaluating a condition fails