com.saxonica.expr

Class IndexedValue<T extends Item>

java.lang.Object

com.saxonica.expr.IndexedValue<T>

All Implemented Interfaces:

GroundedValue, Sequence

public class IndexedValue<T extends Item>
extends Object
implements GroundedValue

A representation of a (sequence) value that allows the construction of one or more indexes to provide rapid access to the items in the sequence.

Constructor Summary

Constructors

Constructor and Description
IndexedValue(SequenceIterator<? extends T> iter) Construct an indexed value (that is, a value that is capable of being indexed).

Method Summary

Methods

Modifier and Type	Method and Description
boolean	effectiveBooleanValue() Get the effective boolean value of this sequence
SequenceIterator<T>	findItems(Expression use, SequenceIterator values, boolean convertUntypedToOther, boolean firstOnly, AtomicComparer comparer, XPathContext context) Retrieve items that match a given index value
int	getLength() Get the length of the sequence
String	getStringValue() Get the string value of this sequence.
CharSequence	getStringValueCS() Get the string value of this sequence.
Item	head() Get the first item in the sequence.
T	itemAt(int n) Get the n'th item in the sequence (starting from 0).
SequenceIterator<T>	iterate() Return an Iterator to iterate over the values of a sequence.
GroundedValue	reduce() Reduce the sequence to its simplest form.
GroundedValue	subsequence(int start, int length) Get a subsequence of the value

Methods inherited from class java.lang.Object

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

Constructor Detail

IndexedValue

public IndexedValue(SequenceIterator<? extends T> iter)
             throws XPathException

Construct an indexed value (that is, a value that is capable of being indexed). Initially there will be no indexes, these are added later.

Parameters:

iter - iterator over the items to be included in the indexed value

Throws:

XPathException - if an error occurs reading the iterator

Method Detail

iterate

public SequenceIterator<T> iterate()
                                         throws XPathException

Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.

Specified by:

iterate in interface Sequence

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

Throws:

XPathException - if any dynamic error occurs evaluating the expression

itemAt

public T itemAt(int n)

Get the n'th item in the sequence (starting from 0). This is defined for all Values, but its real benefits come for a sequence Value stored extensionally (or for a MemoClosure, once all the values have been read)

Specified by:

itemAt in interface GroundedValue

Parameters:

n - position of the required item, counting from zero.

Returns:

the n'th item in the sequence, where the first item in the sequence is numbered zero. If n is negative or >= the length of the sequence, returns null.

getLength

public int getLength()

Get the length of the sequence

Specified by:

getLength in interface GroundedValue

Returns:

the number of items in the sequence

findItems

public SequenceIterator<T> findItems(Expression use,
                            SequenceIterator values,
                            boolean convertUntypedToOther,
                            boolean firstOnly,
                            AtomicComparer comparer,
                            XPathContext context)
                                           throws XPathException

Retrieve items that match a given index value

Parameters:

use - the expression whose value is to be matched

values - the set of values to be found

convertUntypedToOther - true if untypedAtomic values are to be converted to the type of the other operand

firstOnly - true if only the first matching item is required

comparer - AtomicComparer used to compare values for equality (encapsulates a collation if necessary)

context - the dynamic evaluation context @return an iterator over the items that match the specified values

Throws:

XPathException

subsequence

public GroundedValue subsequence(int start,
                        int length)

Get a subsequence of the value

Specified by:

subsequence in interface GroundedValue

Parameters:

start - the index of the first item to be included in the result, counting from zero. A negative value is taken as zero. If the value is beyond the end of the sequence, an empty sequence is returned

length - the number of items to be included in the result. Specify Integer.MAX_VALUE to get the subsequence up to the end of the base sequence. If the value is negative, an empty sequence is returned. If the value goes off the end of the sequence, the result returns items up to the end of the sequence

Returns:

the required subsequence. If min is

effectiveBooleanValue

public boolean effectiveBooleanValue()
                              throws XPathException

Description copied from interface: GroundedValue

Get the effective boolean value of this sequence

Specified by:

effectiveBooleanValue in interface GroundedValue

Returns:

the effective boolean value

Throws:

XPathException - if the sequence has no effective boolean value (for example a sequence of two integers)

getStringValue

public String getStringValue()
                      throws XPathException

Description copied from interface: GroundedValue

Get the string value of this sequence. The string value of an item is the result of applying the string() function. The string value of a sequence is the space-separated result of applying the string-join() function using a single space as the separator

Specified by:

getStringValue in interface GroundedValue

Returns:

the string value of the sequence.

Throws:

XPathException - if the sequence contains items that have no string value (for example, function items)

getStringValueCS

public CharSequence getStringValueCS()
                              throws XPathException

Description copied from interface: GroundedValue

Get the string value of this sequence. The string value of an item is the result of applying the string() function. The string value of a sequence is the space-separated result of applying the string-join() function using a single space as the separator

Specified by:

getStringValueCS in interface GroundedValue

Returns:

the string value of the sequence.

Throws:

XPathException - if the sequence contains items that have no string value (for example, function items)

head

public Item head()
          throws XPathException

Get the first item in the sequence.

Specified by:

head in interface Sequence

Returns:

the first item in the sequence if there is one, or null if the sequence is empty

Throws:

XPathException - in the situation where the sequence is evaluated lazily, and evaluation of the first item causes a dynamic error.

reduce

public GroundedValue reduce()

Reduce the sequence to its simplest form. If the value is an empty sequence, the result will be EmptySequence.getInstance(). If the value is a single atomic value, the result will be an instance of AtomicValue. If the value is a single item of any other kind, the result will be an instance of SingletonItem. Otherwise, the result will typically be unchanged.

Specified by:

reduce in interface GroundedValue

Returns:

the simplified sequence