Package org.basex.query.value.seq

Class SingletonSeq

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.value.Value

org.basex.query.value.seq.Seq

org.basex.query.value.seq.SingletonSeq

All Implemented Interfaces:

Iterable<Item>

public final class SingletonSeq
extends Seq

Sequence of a single item.

Author:

BaseX Team 2005-21, BSD License, Christian Gruen

Field Summary

Fields inherited from class org.basex.query.value.seq.Seq

size

Fields inherited from class org.basex.query.value.Value

type

Method Summary

Modifier and Type	Method	Description
long	atomSize()	Computes the number of atomized items.
Value	atomValue(QueryContext qc, InputInfo ii)	Evaluates the expression and returns the atomized items.
void	cache(boolean lazy, InputInfo ii)	Caches lazy values.
String	description()	Returns a string description of the expression.
Item	ebv(QueryContext qc, InputInfo ii)	Checks if the effective boolean value can be computed for this expression:
static Value	get(Value value, long count)	Creates a singleton sequence with the specified value.
Value	insert(long pos, Item item, QueryContext qc)	Inserts an item at the given position into this sequence and returns the resulting sequence.
Item	itemAt(long pos)	Returns the item at the given position in the value.
void	plan(QueryPlan plan)	Creates a query plan.
void	plan(QueryString qs)	Creates a query string.
Value	remove(long pos, QueryContext qc)	Removes the item at the given position in this sequence and returns the resulting sequence.
Value	reverse(QueryContext qc)	Returns all items of this value in reverse order.
Expr	simplifyFor(CompileContext.Simplify mode, CompileContext cc)	This function is called at compile time for expressions whose operands might be simplified.
boolean	singleItem()	Indicates if the sequence is based on a single item.
protected Seq	subSeq(long offset, long length, QueryContext qc)	Returns a sub sequence of this value with the given start and length.

Methods inherited from class org.basex.query.value.seq.Seq

copyInsert, ddo, equals, get, hash, initialCapacity, insertBefore, item, iter, refineType, seqType, size, subsequence, test, toErrorString, toJava

Methods inherited from class org.basex.query.value.Value

accept, checkUp, compile, copy, count, exprSize, has, inline, inlineable, isEmpty, isItem, iter, iterator, materialize, serialize, serialize, serialize, value

Methods inherited from class org.basex.query.expr.Expr

arg, args, atomItem, atomIter, data, data, funcType, hasFreeVars, indexAccessible, isSimple, markTailCalls, mergeEbv, optimize, typeCheck, uses, vacuous, visitAll

Methods inherited from class org.basex.query.expr.ExprInfo

toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Method Details

ebv

public Item ebv(QueryContext qc,
 InputInfo ii)
         throws QueryException

Description copied from class: Expr

Checks if the effective boolean value can be computed for this expression:

• If it yields an empty sequence, Bln.FALSE will be returned.
• If it yields a single item, this item will be returned.
• If it yields nodes, the first node will be returned.
• Otherwise, an error will be raised.

A single numeric item may later be evaluated as positional predicate.

Specified by:

ebv in class Expr

Parameters:

qc - query context

ii - input info (required for Seq instances, which have no input info)

Returns:

item

Throws:

QueryException - query exception

cache

public void cache(boolean lazy,
 InputInfo ii)
           throws QueryException

Description copied from class: Value

Caches lazy values.

Specified by:

cache in class Value

Parameters:

lazy - lazy caching

ii - input info

Throws:

QueryException - query exception

atomValue

public Value atomValue(QueryContext qc,
 InputInfo ii)
                throws QueryException

Description copied from class: Expr

Evaluates the expression and returns the atomized items.

Specified by:

atomValue in class Expr

Parameters:

qc - query context

ii - input info (only required by Seq instances, which have no input info)

Returns:

atomized item

Throws:

QueryException - query exception

atomSize

public long atomSize()

Description copied from class: Value

Computes the number of atomized items.

Specified by:

atomSize in class Value

Returns:

atomized item

subSeq

protected Seq subSeq(long offset,
 long length,
 QueryContext qc)

Description copied from class: Seq

Returns a sub sequence of this value with the given start and length.

Overrides:

subSeq in class Seq

Parameters:

offset - offset (ge 0)

length - number of items (1 lt length lt size())

qc - query context

Returns:

sub sequence

insert

public Value insert(long pos,
 Item item,
 QueryContext qc)

Description copied from class: Seq

Inserts an item at the given position into this sequence and returns the resulting sequence.

Specified by:

insert in class Seq

Parameters:

pos - position at which the item should be inserted, must be between 0 and Seq.size

item - item to insert

qc - query context

Returns:

resulting value

remove

public Value remove(long pos,
 QueryContext qc)

Description copied from class: Seq

Removes the item at the given position in this sequence and returns the resulting sequence.

Specified by:

remove in class Seq

Parameters:

pos - position of the item to remove, must be between 0 and Seq.size - 1

qc - query context

Returns:

resulting sequence

reverse

public Value reverse(QueryContext qc)

Description copied from class: Value

Returns all items of this value in reverse order.

Specified by:

reverse in class Value

Parameters:

qc - query context

Returns:

items in reverse order

itemAt

public Item itemAt(long pos)

Description copied from class: Value

Returns the item at the given position in the value. The specified value must be lie within the valid bounds.

Specified by:

itemAt in class Value

Parameters:

pos - position

Returns:

item

simplifyFor

public Expr simplifyFor(CompileContext.Simplify mode,
 CompileContext cc)
                 throws QueryException

Description copied from class: Expr

This function is called at compile time for expressions whose operands might be simplified.

Overrides:

simplifyFor in class Expr

Parameters:

mode - mode of simplification

cc - compilation context

Returns:

simplified or original expression

Throws:

QueryException - query exception

See Also:

• CompileContext.Simplify

description

public String description()

Description copied from class: ExprInfo

Returns a string description of the expression. This method is only called by error messages. Contrary to the ExprInfo.toString() method, arguments are not included in the output.

Overrides:

description in class Seq

Returns:

result of check

plan

public void plan(QueryPlan plan)

Description copied from class: ExprInfo

Creates a query plan.

Overrides:

plan in class Seq

Parameters:

plan - expression plan

plan

public void plan(QueryString qs)

Description copied from class: ExprInfo

Creates a query string.

Overrides:

plan in class Seq

Parameters:

qs - query string builder

singleItem

public boolean singleItem()

Indicates if the sequence is based on a single item.

Returns:

result of check

get

public static Value get(Value value,
 long count)

Creates a singleton sequence with the specified value.

Parameters:

value - value

count - number of repetitions

Returns:

value