org.basex.query.xpath.item
Class Item

java.lang.Object
  org.basex.query.ExprInfo
      org.basex.query.xpath.expr.Expr
          org.basex.query.xpath.item.Item

All Implemented Interfaces:

Result

Direct Known Subclasses:

Bln, Dbl, Nod, Str

public abstract class Item
extends Expr
implements Result

Interface for all XPath items (results of expressions).

Author:

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

Constructor Summary

Item()

Method Summary

abstract boolean	bool() Returns the boolean value.
Expr	comp(XPContext ctx) Optimizes the expression.
abstract boolean	eq(Item v) Checks the equality of the value and the specified value.
abstract double	num() Returns the double value.
boolean	same(Result v) Compares values for equality.
void	serialize(Serializer ser) Serializes the complete result.
void	serialize(Serializer ser, int n) Serializes the specified result.
int	size() Number of values, stored in the result instance.
abstract byte[]	str() Returns the literal value.
abstract java.lang.String	toString()
boolean	usesPos() Checks whether this Expression (or its children) make use of the position parameter.
boolean	usesSize() Checks whether this Expression (or its children) make use of the setsize parameter.

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

eval, indexEquivalent, indexSizes, returnedValue, sameAs

Methods inherited from class org.basex.query.ExprInfo

color, info, name, plan

Methods inherited from class java.lang.Object

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

Constructor Detail

Item

public Item()

Method Detail

bool

public abstract boolean bool()

Returns the boolean value.

Returns:

boolean value

str

public abstract byte[] str()

Returns the literal value.

Returns:

literal value

num

public abstract double num()

Returns the double value.

Returns:

double value

eq

public abstract boolean eq(Item v)

Checks the equality of the value and the specified value.

Parameters:

v - value to be compared

Returns:

result of comparison.

comp

public final Expr comp(XPContext ctx)

Description copied from class: Expr

Optimizes the expression.

Specified by:

comp in class Expr

Parameters:

ctx - expression context

Returns:

optimized Expression

usesSize

public final boolean usesSize()

Description copied from class: Expr

Checks whether this Expression (or its children) make use of the setsize parameter. If not this allows early predicate evaluation.

Specified by:

usesSize in class Expr

Returns:

whether setsize is used

usesPos

public final boolean usesPos()

Description copied from class: Expr

Checks whether this Expression (or its children) make use of the position parameter. If not this allows some nice optimizations.

Specified by:

usesPos in class Expr

Returns:

whether position is used

toString

public abstract java.lang.String toString()

Specified by:

toString in class ExprInfo

size

public int size()

Number of values, stored in the result instance.

Specified by:

size in interface Result

Returns:

number of values

same

public final boolean same(Result v)

Compares values for equality.

Specified by:

same in interface Result

Parameters:

v - value to be compared

Returns:

true if values are equal

serialize

public void serialize(Serializer ser)
               throws java.io.IOException

Serializes the complete result.

Specified by:

serialize in interface Result

Parameters:

ser - serializer

Throws:

java.io.IOException - exception

serialize

public void serialize(Serializer ser,
                      int n)
               throws java.io.IOException

Serializes the specified result.

Specified by:

serialize in interface Result

Parameters:

ser - serializer

n - number of result to serialize

Throws:

java.io.IOException - exception