org.basex.query.xquery.iter
Class Iter

java.lang.Object
  org.basex.query.xquery.iter.Iter

Direct Known Subclasses:

NodeIter, RangeIter, SeqIter

public abstract class Iter
extends java.lang.Object

Iterator interface.

Author:

Workgroup DBIS, University of Konstanz 2005-08, ISC License, Christian Gruen

Field Summary

static Iter

EMPTY Empty iterator.

Constructor Summary

Iter()

Method Summary

Item	atomic(Expr expr, boolean empty) Checks if the specified iterator contains a single item.
Item	ebv() Checks if the iterator can be dissolved into an effective boolean value.
Item	finish() Returns a sequence from all iterator values.
abstract Item	next() Returns the next item or null if no other items are found.
void	reset() Resets the iterator; can be optionally implemented.
static void	seqErr(Item i1, Item i2, Item i3, Expr expr) Throws a sequence error.
long	size() Returns the number of entries.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

EMPTY

public static final Iter EMPTY

Empty iterator.

Constructor Detail

Iter

public Iter()

Method Detail

next

public abstract Item next()
                   throws XQException

Returns the next item or null if no other items are found.

Returns:

resulting item

Throws:

XQException - evaluation exception

reset

public void reset()

Resets the iterator; can be optionally implemented.

size

public long size()

Returns the number of entries. Warning: -1 is returned if the number cannot be evaluated, so each method has to check and react on the returned value.

Returns:

number of entries

finish

public Item finish()
            throws XQException

Returns a sequence from all iterator values.

Returns:

sequence

Throws:

XQException - evaluation exception

ebv

public final Item ebv()
               throws XQException

Checks if the iterator can be dissolved into an effective boolean value. If not, returns an error. If yes, returns the first value - which can be also be e.g. an integer, which is later evaluated as position predicate. Must be called before next() was called.

Returns:

item

Throws:

XQException - evaluation exception

atomic

public final Item atomic(Expr expr,
                         boolean empty)
                  throws XQException

Checks if the specified iterator contains a single item. Returns null, the first item or an exception.

Parameters:

expr - calling expression

empty - allow empty sequences

Returns:

item

Throws:

XQException - evaluation exception

seqErr

public static void seqErr(Item i1,
                          Item i2,
                          Item i3,
                          Expr expr)
                   throws XQException

Throws a sequence error.

Parameters:

i1 - first item

i2 - first item

i3 - first item

expr - expression

Throws:

XQException - evaluation exception