org.basex.query.xpath.values
Class Item

java.lang.Object
  org.basex.query.xpath.expr.Expr
      org.basex.query.xpath.values.Item

All Implemented Interfaces:

Result

Direct Known Subclasses:

Bool, Literal, NodeSet, Num

public abstract class Item
extends Expr
implements Result

Interface for all XPath items (results of expressions).

Author:

Workgroup DBIS, University of Konstanz 2005-07, ISC License, Tim Petrowsky

Constructor Summary

Item()

Method Summary

abstract boolean	bool() Returns the boolean value.
Expr	compile(XPContext ctx) Tries to optimize 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	sameAs(Result v) Compares values for equality.
void	serialize(PrintOutput out, boolean valid) Serializes the stored data to the specified output stream.
void	serialize(ResultReader rr) Serializes the stored data to the specified reader.
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 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

compile

public final Expr compile(XPContext ctx)

Description copied from class: Expr

Tries to optimize the Expression.

Specified by:

compile in class Expr

Parameters:

ctx - expression context

Returns:

optimized Expression

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.

num

public abstract double num()

Returns the double value.

Returns:

double value

sameAs

public final boolean sameAs(Result v)

Compares values for equality.

Specified by:

sameAs in interface Result

Parameters:

v - value to be compared

Returns:

true if values are equal

serialize

public final void serialize(PrintOutput out,
                            boolean valid)
                     throws java.io.IOException

Serializes the stored data to the specified output stream.

Specified by:

serialize in interface Result

Parameters:

out - output stream

valid - well-formed output

Throws:

java.io.IOException - in case of problems with the PrintOutput

serialize

public final void serialize(ResultReader rr)

Serializes the stored data to the specified reader.

Specified by:

serialize in interface Result

Parameters:

rr - default handler

size

public int size()

Number of values, stored in the result instance.

Specified by:

size in interface Result

Returns:

number of values

str

public abstract byte[] str()

Returns the literal value.

Returns:

literal value

toString

public abstract java.lang.String toString()

Specified by:

toString in class Expr

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

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