net.sf.saxon.functions
Class Minimax

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.FunctionCall
          net.sf.saxon.functions.SystemFunction
              net.sf.saxon.functions.CollatingFunction
                  net.sf.saxon.functions.Minimax

All Implemented Interfaces:

Serializable, SourceLocator, EvaluableItem, SequenceIterable, InstructionInfoProvider

public class Minimax
extends CollatingFunction

This class implements the min() and max() functions

See Also:

Serialized Form

Field Summary

static int	MAX
static int	MIN

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

Minimax()

Method Summary

void	checkArguments(ExpressionVisitor visitor) Static analysis: prevent sorting of the argument
int	computeCardinality() Determine the cardinality of the function.
Item	evaluateItem(XPathContext context) Evaluate the function
ItemType	getItemType(TypeHierarchy th) Determine the item type of the value returned by the function
boolean	isIgnoreNaN() Test whether NaN values are to be ignored
static AtomicValue	minimax(SequenceIterator iter, int operation, AtomicComparer atomicComparer, boolean ignoreNaN, XPathContext context) Static method to evaluate the minimum or maximum of a sequence
Expression	optimize(ExpressionVisitor visitor, ItemType contextItemType) Perform optimisation of an expression and its subexpressions.
void	setIgnoreNaN(boolean ignore) Indicate whether NaN values should be ignored.

Methods inherited from class net.sf.saxon.functions.CollatingFunction

copy, getExpressionBaseURI, getStringCollator

Methods inherited from class net.sf.saxon.functions.SystemFunction

addDocToPathMap, computeSpecialProperties, getDetails, getErrorCodeForTypeErrors, makeSystemFunction, setDetails

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

addExternalFunctionCallToPathMap, equals, explain, getArguments, getDisplayName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionName, simplify, toString, typeCheck

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, effectiveBooleanValue, evaluateAsString, explain, findParentOf, getCardinality, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, markTailFunctionCalls, process, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Field Detail

MIN

public static final int MIN

See Also:

Constant Field Values

MAX

public static final int MAX

See Also:

Constant Field Values

Constructor Detail

Minimax

public Minimax()

Method Detail

setIgnoreNaN

public void setIgnoreNaN(boolean ignore)

Indicate whether NaN values should be ignored. For the external min() and max() function, a NaN value in the input causes the result to be NaN. Internally, however, min() and max() are also used in such a way that NaN values should be ignored.

Parameters:

ignore - true if NaN values are to be ignored when computing the min or max.

isIgnoreNaN

public boolean isIgnoreNaN()

Test whether NaN values are to be ignored

Returns:

true if NaN values are to be ignored. This is the case for internally-generated min() and max() functions used to support general comparisons

checkArguments

public void checkArguments(ExpressionVisitor visitor)
                    throws XPathException

Static analysis: prevent sorting of the argument

Overrides:

checkArguments in class CollatingFunction

Parameters:

visitor - the expression visitor

Throws:

XPathException

computeCardinality

public int computeCardinality()

Determine the cardinality of the function.

Overrides:

computeCardinality in class SystemFunction

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

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ItemType contextItemType)
                    throws XPathException

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.

Overrides:

optimize in class SystemFunction

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 Type.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)

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the item type of the value returned by the function

Overrides:

getItemType in class SystemFunction

Parameters:

th - the type hierarchy cache

Returns:

the statically inferred type of the expression

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the function

Specified by:

evaluateItem in interface EvaluableItem

Overrides:

evaluateItem in class Expression

Parameters:

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

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

minimax

public static AtomicValue minimax(SequenceIterator iter,
                                  int operation,
                                  AtomicComparer atomicComparer,
                                  boolean ignoreNaN,
                                  XPathContext context)
                           throws XPathException

Static method to evaluate the minimum or maximum of a sequence

Parameters:

iter - Iterator over the input sequence

operation - either MIN or MAX

atomicComparer - an AtomicComparer used to compare values

ignoreNaN - true if NaN values are to be ignored

context - dynamic evaluation context

Returns:

the min or max value in the sequence, according to the rules of the fn:min() or fn:max() functions

Throws:

XPathException - typically if non-comparable values are found in the sequence