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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.expr;
import net.sf.saxon.evpull.EventIterator;
import net.sf.saxon.evpull.EventMappingFunction;
import net.sf.saxon.evpull.EventMappingIterator;
import net.sf.saxon.expr.instruct.Choose;
import net.sf.saxon.expr.parser.*;
import net.sf.saxon.functions.SystemFunctionCall;
import net.sf.saxon.lib.FeatureKeys;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.om.StructuredQName;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trace.Location;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.ItemType;
import net.sf.saxon.type.SchemaType;
import net.sf.saxon.type.TypeHierarchy;
import net.sf.saxon.value.Cardinality;
import net.sf.saxon.value.Int64Value;
import net.sf.saxon.value.IntegerValue;
import net.sf.saxon.value.SequenceType;
import java.util.ArrayList;
import java.util.List;
/**
* A ForExpression maps an expression over a sequence.
* This version works with range variables, it doesn't change the context information
*/
public class ForExpression extends Assignation {
/*@Nullable*/ protected PositionVariable positionVariable = null;
int actionCardinality = StaticProperty.ALLOWS_MANY;
/**
* Create a "for" expression (for $x at $p in SEQUENCE return ACTION)
*/
public ForExpression() {
}
/**
* Get a name identifying the kind of expression, in terms meaningful to a user.
* @return a name identifying the kind of expression, in terms meaningful to a user.
* The name will always be in the form of a lexical XML QName, and should match the name used
* in explain() output displaying the expression.
*/
public String getExpressionName() {
return "for";
}
/**
* Set the reference to the position variable (XQuery only)
* @param decl the range variable declaration for the position variable
*/
public void setPositionVariable (PositionVariable decl) {
positionVariable = decl;
}
/*@Nullable*/ public PositionVariable getPositionVariable () {
return positionVariable;
}
public boolean hasVariableBinding(Binding binding){
return this == binding || positionVariable == binding;
}
/**
* Get the name of the position variable
* @return the name of the position variable ("at $p") if there is one, or null if not
*/
/*@Nullable*/ public StructuredQName getPositionVariableName() {
if (positionVariable == null) {
return null;
} else {
return positionVariable.getVariableQName();
}
}
/**
* Set the slot number for the range variable
* @param nr the slot number allocated to the range variable on the local stack frame.
* This implicitly allocates the next slot number to the position variable if there is one.
*/
public void setSlotNumber(int nr) {
super.setSlotNumber(nr);
if (positionVariable != null) {
positionVariable.setSlotNumber(nr+1);
}
}
/**
* Get the number of slots required.
* @return normally 1, except for a FOR expression with an AT clause, where it is 2.
*/
public int getRequiredSlots() {
return (positionVariable == null ? 1 : 2);
}
/**
* Type-check the expression
*/
/*@NotNull*/
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
// The order of events is critical here. First we ensure that the type of the
// sequence expression is established. This is used to establish the type of the variable,
// which in turn is required when type-checking the action part.
sequence = visitor.typeCheck(sequence, contextItemType);
if (Literal.isEmptySequence(sequence)) {
return sequence;
}
if (requiredType != null) {
// if declaration is null, we've already done the type checking in a previous pass
final TypeHierarchy th = visitor.getConfiguration().getTypeHierarchy();
SequenceType decl = requiredType;
SequenceType sequenceType = SequenceType.makeSequenceType(
decl.getPrimaryType(), StaticProperty.ALLOWS_ZERO_OR_MORE);
RoleLocator role = new RoleLocator(RoleLocator.VARIABLE, variableName, 0
);
//role.setSourceLocator(this);
sequence = TypeChecker.strictTypeCheck(
sequence, sequenceType, role, visitor.getStaticContext());
ItemType actualItemType = sequence.getItemType(th);
refineTypeInformation(actualItemType,
getRangeVariableCardinality(),
null,
sequence.getSpecialProperties(), visitor, this);
}
action = visitor.typeCheck(action, contextItemType);
if (Literal.isEmptySequence(action)) {
return action;
}
actionCardinality = action.getCardinality();
return this;
}
/**
* Get the cardinality of the range variable
* @return the cardinality of the range variable (StaticProperty.EXACTLY_ONE). Can be overridden
* in a subclass
*/
protected int getRangeVariableCardinality() {
return StaticProperty.EXACTLY_ONE;
}
/**
* Optimize the expression
*/
/*@NotNull*/
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
Optimizer opt = visitor.getConfiguration().obtainOptimizer();
boolean debug = opt.getConfiguration().getBooleanProperty(FeatureKeys.TRACE_OPTIMIZER_DECISIONS);
// Try to promote any WHERE clause appearing immediately within the FOR expression
if (Choose.isSingleBranchChoice(action)) {
Expression act2 = visitor.optimize(action, contextItemType);
if (act2 != action) {
action = act2;
adoptChildExpression(action);
visitor.resetStaticProperties();
}
}
Expression p = promoteWhereClause(positionVariable);
if (p != null) {
if (debug) {
opt.trace("Promoted where clause in for $" + getVariableName(), p);
}
return visitor.optimize(p, contextItemType);
}
// See if there is a simple "where" condition that can be turned into a predicate
// Expression pred = convertWhereToPredicate(visitor, contextItemType);
// if (pred != null) {
// if (debug) {
// opt.trace("Converted where clause in for $" + getVariableName() + " to predicate", pred);
// }
// if (pred != this) {
// return visitor.optimize(pred, contextItemType);
// }
// }
Expression seq2 = visitor.optimize(sequence, contextItemType);
if (seq2 != sequence) {
sequence = seq2;
adoptChildExpression(sequence);
visitor.resetStaticProperties();
return optimize(visitor, contextItemType);
}
if (Literal.isEmptySequence(sequence)) {
return sequence;
}
Expression act2 = visitor.optimize(action, contextItemType);
if (act2 != action) {
action = act2;
adoptChildExpression(action);
visitor.resetStaticProperties();
// it's now worth re-attempting the "where" clause optimizations
return optimize(visitor, contextItemType);
}
if (Literal.isEmptySequence(action)) {
return action;
}
Expression e2 = extractLoopInvariants(visitor, contextItemType);
if (e2 != null && e2 != this) {
if (debug) {
opt.trace("Extracted invariant in 'for $" + getVariableName() + "' loop", e2);
}
return visitor.optimize(e2, contextItemType);
}
// Simplify an expression of the form "for $b in a/b/c return $b/d".
// (XQuery users seem to write these a lot!)
if (positionVariable==null &&
sequence instanceof SlashExpression && action instanceof SlashExpression) {
SlashExpression path2 = (SlashExpression)action;
Expression start2 = path2.getControllingExpression();
Expression step2 = path2.getControlledExpression();
if (start2 instanceof VariableReference && ((VariableReference)start2).getBinding() == this &&
ExpressionTool.getReferenceCount(action, this, false) == 1 &&
((step2.getDependencies() & (StaticProperty.DEPENDS_ON_POSITION | StaticProperty.DEPENDS_ON_LAST)) == 0)) {
Expression newPath = new SlashExpression(sequence, path2.getControlledExpression());
ExpressionTool.copyLocationInfo(this, newPath);
newPath = visitor.typeCheck(visitor.simplify(newPath), contextItemType);
if (newPath instanceof SlashExpression) {
// if not, it has been wrapped in a DocumentSorter or Reverser, which makes it ineligible.
// see test qxmp299, where this condition isn't satisfied
if (debug) {
opt.trace("Collapsed return clause of for $" + getVariableName() +
" into path expression", newPath);
}
return visitor.optimize(newPath, contextItemType);
}
}
}
// Simplify an expression of the form "for $x in EXPR return $x". These sometimes
// arise as a result of previous optimization steps.
if (action instanceof VariableReference && ((VariableReference)action).getBinding() == this) {
if (debug) {
opt.trace("Collapsed redundant for expression $" + getVariableName(), sequence);
}
return sequence;
}
// Rewrite an expression of the form "for $x at $p in EXPR return $p" as "1 to count(EXPR)"
if (action instanceof VariableReference && ((VariableReference)action).getBinding() == positionVariable) {
FunctionCall count = SystemFunctionCall.makeSystemFunction("count", new Expression[]{sequence});
RangeExpression range = new RangeExpression(Literal.makeLiteral(Int64Value.PLUS_ONE), Token.TO, count);
if (debug) {
opt.trace("Replaced 'for $x at $p in EXP return $p' by '1 to count(EXP)'", range);
}
return range.optimize(visitor, contextItemType);
}
// If the cardinality of the sequence is exactly one, rewrite as a LET expression
if (sequence.getCardinality() == StaticProperty.EXACTLY_ONE) {
LetExpression let = new LetExpression();
let.setVariableQName(variableName);
let.setRequiredType(SequenceType.makeSequenceType(
sequence.getItemType(visitor.getConfiguration().getTypeHierarchy()),
StaticProperty.EXACTLY_ONE));
let.setSequence(sequence);
let.setAction(action);
let.setSlotNumber(slotNumber);
ExpressionTool.rebindVariableReferences(action, this, let);
if (positionVariable != null) {
LetExpression let2 =new LetExpression();
let2.setVariableQName(positionVariable.getVariableQName());
let2.setSequence(Literal.makeLiteral(IntegerValue.PLUS_ONE));
let2.setAction(let);
let2.setSlotNumber(positionVariable.getLocalSlotNumber());
let2.setRequiredType(SequenceType.SINGLE_INTEGER);
ExpressionTool.rebindVariableReferences(let, positionVariable, let2);
let = let2;
}
return let.typeCheck(visitor, contextItemType).optimize(visitor, contextItemType);
}
if (visitor.isOptimizeForStreaming() && positionVariable == null) {
Expression e3 = visitor.getConfiguration().obtainOptimizer().optimizeForExpressionForStreaming(this);
if (e3 != this) {
return visitor.optimize(e3, contextItemType);
}
}
//declaration = null; // let the garbage collector take it
return this;
}
/**
* Replace this expression by an expression that returns the same result but without
* regard to order
*
* @param retainAllNodes true if all nodes in the result must be retained; false
* if duplicates can be eliminated
*/
@Override
public Expression unordered(boolean retainAllNodes) throws XPathException {
action = action.unordered(retainAllNodes);
if (positionVariable == null) {
sequence = sequence.unordered(retainAllNodes);
}
return this;
}
/**
* For an expression that returns an integer or a sequence of integers, get
* a lower and upper bound on the values of the integers that may be returned, from
* static analysis. The default implementation returns null, meaning "unknown" or
* "not applicable". Other implementations return an array of two IntegerValue objects,
* representing the lower and upper bounds respectively. The values
* UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that
* the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH
* are used to indicate values limited by the size of a string or the size of a sequence.
*
* @return the lower and upper bounds of integer values in the result, or null to indicate
* unknown or not applicable.
*/
/*@Nullable*/@Override
public IntegerValue[] getIntegerBounds() {
return action.getIntegerBounds();
}
/**
* Extract subexpressions in the action part that don't depend on the range variable
* @param visitor the expression visitor
* @param contextItemType the item type of the context item
* @return the optimized expression if it has changed, or null if no optimization was possible
*/
private Expression extractLoopInvariants(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException {
// Extract subexpressions that don't depend on the range variable or the position variable
// If a subexpression is (or might be) creative, this is, if it creates new nodes, we don't
// extract it from the loop, but we do extract its non-creative subexpressions
//if (positionVariable == null) {
PromotionOffer offer = new PromotionOffer(visitor.getConfiguration().obtainOptimizer());
offer.containingExpression = this;
offer.action = PromotionOffer.RANGE_INDEPENDENT;
if (positionVariable == null) {
offer.bindingList = new Binding[] {this};
} else {
offer.bindingList = new Binding[] {this, positionVariable};
}
action = doPromotion(action, offer);
if (offer.containingExpression instanceof LetExpression) {
// a subexpression has been promoted
//offer.containingExpression.setParentExpression(container);
// try again: there may be further subexpressions to promote
offer.containingExpression = visitor.optimize(offer.containingExpression, contextItemType);
}
return offer.containingExpression;
//}
//return null;
}
/**
* Promote a WHERE clause whose condition doesn't depend on the variable being bound.
* This rewrites an expression of the form
*
* let $i := SEQ return if (C) then R else ()
* to the form:
* if (C) then (let $i := SEQ return R) else ()
*
* @param positionBinding the binding of the position variable if any
* @return an expression in which terms from the WHERE clause that can be extracted have been extracted
*/
/*@Nullable*/ protected Expression promoteWhereClause(/*@Nullable*/ Binding positionBinding) {
if (Choose.isSingleBranchChoice(action)) {
Expression condition = ((Choose)action).getConditions()[0];
Binding[] bindingList;
if (positionBinding == null) {
bindingList = new Binding[] {this};
} else {
bindingList = new Binding[] {this, positionBinding};
}
List list = new ArrayList(5);
Expression promotedCondition = null;
BooleanExpression.listAndComponents(condition, list);
for (int i = list.size() - 1; i >= 0; i--) {
Expression term = (Expression) list.get(i);
if (!ExpressionTool.dependsOnVariable(term, bindingList)) {
if (promotedCondition == null) {
promotedCondition = term;
} else {
promotedCondition = new AndExpression(term, promotedCondition);
}
list.remove(i);
}
}
if (promotedCondition != null) {
if (list.isEmpty()) {
// the whole if() condition has been promoted
Expression oldThen = ((Choose)action).getActions()[0];
setAction(oldThen);
return Choose.makeConditional(condition, this);
} else {
// one or more terms of the if() condition have been promoted
Expression retainedCondition = (Expression) list.get(0);
for (int i = 1; i < list.size(); i++) {
retainedCondition = new AndExpression(retainedCondition, (Expression) list.get(i));
}
((Choose)action).getConditions()[0] = retainedCondition;
Expression newIf = Choose.makeConditional(
promotedCondition, this, Literal.makeEmptySequence());
ExpressionTool.copyLocationInfo(this, newIf);
return newIf;
}
}
}
return null;
}
/**
* Copy an expression. This makes a deep copy.
* @return the copy of the original expression
*/
/*@NotNull*/
public Expression copy() {
ForExpression forExp = new ForExpression();
forExp.setRequiredType(requiredType);
forExp.setVariableQName(variableName);
forExp.setSequence(sequence.copy());
Expression newAction = action.copy();
forExp.setAction(newAction);
forExp.variableName = variableName;
forExp.slotNumber = slotNumber;
ExpressionTool.rebindVariableReferences(newAction, this, forExp);
if (positionVariable != null) {
PositionVariable pv2 = new PositionVariable();
pv2.setVariableQName(positionVariable.getVariableQName());
forExp.setPositionVariable(pv2);
ExpressionTool.rebindVariableReferences(newAction, positionVariable, pv2);
}
return forExp;
}
/**
* Mark tail function calls: only possible if the for expression iterates zero or one times.
* (This arises in XSLT/XPath, which does not have a LET expression, so FOR gets used instead)
*/
public int markTailFunctionCalls(StructuredQName qName, int arity) {
if (!Cardinality.allowsMany(sequence.getCardinality())) {
return ExpressionTool.markTailFunctionCalls(action, qName, arity);
} else {
return UserFunctionCall.NOT_TAIL_CALL;
}
}
/**
* Extend an array of variable bindings to include the binding(s) defined in this expression
*/
public Binding[] extendBindingList(Binding[] in) {
if (positionVariable == null) {
return super.extendBindingList(in);
}
Binding[] newBindingList = new Binding[in.length+2];
System.arraycopy(in, 0, newBindingList, 0, in.length);
newBindingList[in.length] = this;
newBindingList[in.length+1] = positionVariable;
return newBindingList;
}
/**
* Determine whether this is a vacuous expression as defined in the XQuery update specification
* @return true if this expression is vacuous
*/
public boolean isVacuousExpression() {
return action.isVacuousExpression();
}
/**
* 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. This implementation provides both iterate() and
* process() methods natively.
*/
public int getImplementationMethod() {
return ITERATE_METHOD | PROCESS_METHOD;
}
/**
* 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.
*/
public void checkPermittedContents(SchemaType parentType, StaticContext env, boolean whole) throws XPathException {
action.checkPermittedContents(parentType, env, false);
}
/**
* Iterate over the sequence of values
*/
/*@NotNull*/
public SequenceIterator iterate(XPathContext context) throws XPathException {
// First create an iteration of the base sequence.
// Then create a MappingIterator which applies a mapping function to each
// item in the base sequence. The mapping function is essentially the "return"
// expression, wrapped in a MappingAction object that is responsible also for
// setting the range variable at each step.
SequenceIterator base = sequence.iterate(context);
int pslot = (positionVariable == null ? -1 : positionVariable.getLocalSlotNumber());
MappingAction map = new MappingAction(context, getLocalSlotNumber(), pslot, action);
switch (actionCardinality) {
case StaticProperty.EXACTLY_ONE:
return new ItemMappingIterator(base, map, true);
case StaticProperty.ALLOWS_ZERO_OR_ONE:
return new ItemMappingIterator(base, map, false);
default:
return new MappingIterator(base, map);
}
}
/**
* Deliver the result of the expression as a sequence of events.
* @param context The dynamic evaluation context
* @return the result of the expression as an iterator over a sequence of PullEvent objects
* @throws XPathException if a dynamic error occurs during expression evaluation
*/
/*@Nullable*/ public EventIterator iterateEvents(XPathContext context) throws XPathException {
// First create an iteration of the base sequence.
// Then create an EventMappingIterator which applies a mapping function to each
// item in the base sequence. The mapping function is essentially the "return"
// expression, wrapped in an EventMappingAction object that is responsible also for
// setting the range variable at each step.
SequenceIterator base = sequence.iterate(context);
EventMappingFunction map = new EventMappingAction(context, getLocalSlotNumber(), positionVariable, action);
return new EventMappingIterator(base, map);
}
/**
* Process this expression as an instruction, writing results to the current
* outputter
*/
public void process(XPathContext context) throws XPathException {
SequenceIterator iter = sequence.iterate(context);
int position = 1;
int slot = getLocalSlotNumber();
int pslot = -1;
if (positionVariable != null) {
pslot = positionVariable.getLocalSlotNumber();
}
while (true) {
Item item = iter.next();
if (item == null) break;
context.setLocalVariable(slot, item);
if (pslot >= 0) {
context.setLocalVariable(pslot, Int64Value.makeIntegerValue(position++));
}
action.process(context);
}
}
/**
* Evaluate an updating expression, adding the results to a Pending Update List.
* The default implementation of this method, which is used for non-updating expressions,
* throws an UnsupportedOperationException
*
* @param context the XPath dynamic evaluation context
* @param pul the pending update list to which the results should be written
*/
public void evaluatePendingUpdates(XPathContext context, PendingUpdateList pul) throws XPathException {
SequenceIterator iter = sequence.iterate(context);
int position = 1;
int slot = getLocalSlotNumber();
int pslot = -1;
if (positionVariable != null) {
pslot = positionVariable.getLocalSlotNumber();
}
while (true) {
Item item = iter.next();
if (item == null) break;
context.setLocalVariable(slot, item);
if (pslot >= 0) {
context.setLocalVariable(pslot, Int64Value.makeIntegerValue(position++));
}
action.evaluatePendingUpdates(context, pul);
}
}
/**
* Determine the data type of the items returned by the expression, if possible
* @return one of the values Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE,
* or Type.ITEM (meaning not known in advance)
* @param th the type hierarchy cache
*/
/*@NotNull*/
public ItemType getItemType(TypeHierarchy th) {
return action.getItemType(th);
}
/**
* Determine the static cardinality of the expression
*/
public int computeCardinality() {
int c1 = sequence.getCardinality();
int c2 = action.getCardinality();
return Cardinality.multiply(c1, c2);
}
/**
* 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
* @return a representation of the expression as a string
*/
public String toString() {
return "for $" + getVariableEQName() +
" in " + (sequence==null ? "(...)" : sequence.toString()) +
" return " + (action==null ? "(...)" : ExpressionTool.parenthesize(action));
}
/**
* Diagnostic print of expression structure. The abstract expression tree
* is written to the supplied output destination.
*/
public void explain(ExpressionPresenter out) {
out.startElement("for");
explainSpecializedAttributes(out);
out.emitAttribute("variable", getVariableEQName());
out.emitAttribute("as", sequence.getItemType(out.getTypeHierarchy()).toString());
if (positionVariable != null) {
out.emitAttribute("at", positionVariable.getVariableQName().getEQName());
}
out.startSubsidiaryElement("in");
sequence.explain(out);
out.endSubsidiaryElement();
out.startSubsidiaryElement("return");
action.explain(out);
out.endSubsidiaryElement();
out.endElement();
}
protected void explainSpecializedAttributes(ExpressionPresenter out) {
// no action
}
/**
* The MappingAction represents the action to be taken for each item in the
* source sequence. It acts as the MappingFunction for the mapping iterator.
*/
public static class MappingAction implements MappingFunction, ItemMappingFunction, StatefulMappingFunction {
protected XPathContext context;
private int slotNumber;
private Expression action;
private int pslot = -1;
private int position = 1;
public MappingAction() {}
public MappingAction(XPathContext context,
int slotNumber,
int pslot,
Expression action) {
this.context = context;
this.slotNumber = slotNumber;
this.pslot = pslot;
this.action = action;
}
/*@Nullable*/ public SequenceIterator map(Item item) throws XPathException {
context.setLocalVariable(slotNumber, item);
if (pslot >= 0) {
context.setLocalVariable(pslot, Int64Value.makeIntegerValue(position++));
}
return action.iterate(context);
}
/*@Nullable*/ public Item mapItem(Item item) throws XPathException {
context.setLocalVariable(slotNumber, item);
if (pslot >= 0) {
context.setLocalVariable(pslot, Int64Value.makeIntegerValue(position++));
}
return action.evaluateItem(context);
}
public StatefulMappingFunction getAnother() {
// Create a copy of the stack frame, so that changes made to local variables by the cloned
// iterator are not seen by the original iterator
XPathContextMajor c2 = context.newContext();
StackFrame oldstack = context.getStackFrame();
Sequence[] vars = oldstack.getStackFrameValues();
Sequence[] newvars = new Sequence[vars.length];
System.arraycopy(vars, 0, newvars, 0, vars.length);
c2.setStackFrame(oldstack.getStackFrameMap(), newvars);
return new MappingAction(c2, slotNumber, pslot, action);
}
}
/**
* The EventMappingAction represents the action to be taken for each item in the
* source sequence. It acts as the EventMappingFunction for the mapping iterator, and
* also provides the Binding of the position variable (at $n) in XQuery, if used.
*/
protected static class EventMappingAction implements EventMappingFunction {
private XPathContext context;
private int slotNumber;
private Expression action;
private int position = 1;
private int pslot = -1;
public EventMappingAction(XPathContext context,
int slotNumber,
/*@Nullable*/ PositionVariable positionBinding,
Expression action) {
this.context = context;
this.slotNumber = slotNumber;
if (positionBinding != null) {
pslot = positionBinding.getLocalSlotNumber();
}
this.action = action;
}
/*@Nullable*/ public EventIterator map(Item item) throws XPathException {
context.setLocalVariable(slotNumber, item);
if (pslot >= 0) {
context.setLocalVariable(pslot, Int64Value.makeIntegerValue(position++));
}
return action.iterateEvents(context);
}
}
/**
* Get the type of this expression for use in tracing and diagnostics
* @return the type of expression, as enumerated in class {@link net.sf.saxon.trace.Location}
*/
public int getConstructType() {
return Location.FOR_EXPRESSION;
}
}