net.sf.saxon.functions

Class Position

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator

public class Position
extends SystemFunction

Field Summary

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

operation

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

argument

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

Method Summary

Item
evaluateItem(XPathContext c)
Evaluate in a general context
int
getIntrinsicDependencies()
Determine the intrinsic dependencies
Expression
preEvaluate(ExpressionVisitor visitor)
preEvaluate: this method suppresses compile-time evaluation by doing nothing (because the value of the expression depends on the runtime context)
Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Perform type checking of an expression and its subexpressions.

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

addContextDocumentArgument, addDocToPathMap, checkArguments, computeCardinality, computeSpecialProperties, copy, getDetails, getErrorCodeForTypeErrors, getItemType, getRequiredType, makeSystemFunction, optimize, setDetails, useContextItemAsDefault

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

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

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

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Method Details

evaluateItem

public Item evaluateItem(XPathContext c)
            throws XPathException
Evaluate in a general context
Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in interface Expression

getIntrinsicDependencies

public int getIntrinsicDependencies()
Determine the intrinsic dependencies
Overrides:
getIntrinsicDependencies in interface Expression

preEvaluate

public Expression preEvaluate(ExpressionVisitor visitor)
preEvaluate: this method suppresses compile-time evaluation by doing nothing (because the value of the expression depends on the runtime context)
Overrides:
preEvaluate in interface FunctionCall
Parameters:
visitor - an expression visitor

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
            throws XPathException
Perform type checking of an expression and its subexpressions. This is the second phase of static optimization.

This checks statically that the operands of the expression have the correct type; if necessary it generates code to do run-time type checking or type conversion. A static type error is reported only if execution cannot possibly succeed, that is, if a run-time type error is inevitable. The call may return a modified form of the expression.

This method is called after all references to functions and variables have been resolved to the declaration of the function or variable. However, the types of such functions and variables may not be accurately known if they have not been explicitly declared.

If the implementation returns a value other than "this", then it is required to ensure that the parent pointer and location information in the returned expression have been set up correctly. It should not rely on the caller to do this, although for historical reasons many callers do so.

Overrides:
typeCheck in interface FunctionCall
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 to perform necessary run-time type checks, and to perform other type-related optimizations
Throws:
XPathException - if an error is discovered during this phase (typically a type error)