org.basex.query.xpath.expr
Class Pos

java.lang.Object
  org.basex.query.ExprInfo
      org.basex.query.xpath.expr.Expr
          org.basex.query.xpath.expr.Pos

public final class Pos
extends Expr

Position test.

Author:

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

Field Summary

int	max Maximum value.
int	min Minimum value.

Constructor Summary

Pos(int p)
Constructor.

Pos(int mn, int mx)
Constructor.

Method Summary

Expr	comp(XPContext ctx) Optimizes the expression.
static Expr	create(double val, Comp type) Creates a position predicate, a false predicate for impossible comparisons or a null reference.
Bln	eval(XPContext ctx) Evaluates the expression with the specified context set.
void	plan(Serializer ser) Recursively sends the abstract syntax of this expression to the specified serializer.
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

indexEquivalent, indexSizes, returnedValue, sameAs

Methods inherited from class org.basex.query.ExprInfo

color, info, name

Methods inherited from class java.lang.Object

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

Field Detail

min

public int min

Minimum value.

max

public int max

Maximum value.

Constructor Detail

Pos

public Pos(int p)

Constructor.

Parameters:

p - position

Pos

public Pos(int mn,
           int mx)

Constructor.

Parameters:

mn - minimum

mx - maximum

Method Detail

create

public static Expr create(double val,
                          Comp type)

Creates a position predicate, a false predicate for impossible comparisons or a null reference.

Parameters:

val - position value

type - comparison type

Returns:

predicate

comp

public 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

eval

public Bln eval(XPContext ctx)
         throws QueryException

Description copied from class: Expr

Evaluates the expression with the specified context set. Additionally provides a context

Specified by:

eval in class Expr

Parameters:

ctx - query context

Returns:

resulting XPathValue

Throws:

QueryException - evaluation exception

usesPos

public 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 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

plan

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

Description copied from class: ExprInfo

Recursively sends the abstract syntax of this expression to the specified serializer.

Specified by:

plan in class ExprInfo

Parameters:

ser - serializer

Throws:

java.io.IOException - exception

toString

public java.lang.String toString()

Specified by:

toString in class ExprInfo