org.basex.query.expr
Class Pos

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

public final class Pos
extends Simple

Pos Expression.

Author:

Workgroup DBIS, University of Konstanz 2005-09, ISC License, Christian Gruen

Method Summary

Bln	atomic(QueryContext ctx) Evaluates the expression and returns the resulting item or a null reference.
static Expr	get(Expr expr, CmpV.Comp cmp, Expr arg) Returns an instance of this class, if possible, and the input expression otherwise.
static Expr	get(long mn, long mx) Returns an position or an optimized expression.
boolean	last(QueryContext ctx) Returns false if no more results can be expected.
void	plan(Serializer ser) Recursively sends the abstract syntax of this expression to the specified serializer.
Return	returned(QueryContext ctx) Indicates the return type of an expression.
java.lang.String	toString()
boolean	uses(Expr.Use use, QueryContext ctx) Indicates if an expression uses the specified type.

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

color, comp

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

addText, checkCtx, checkDbl, checkItr, duplicates, e, ebv, i, indexAccessible, indexEquivalent, iter, removable, remove, sameAs, size, test

Methods inherited from class org.basex.query.ExprInfo

info, name

Methods inherited from class java.lang.Object

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

Method Detail

get

public static Expr get(long mn,
                       long mx)

Returns an position or an optimized expression.

Parameters:

mn - minimum value

mx - minimum value

Returns:

expression

get

public static Expr get(Expr expr,
                       CmpV.Comp cmp,
                       Expr arg)
                throws QueryException

Returns an instance of this class, if possible, and the input expression otherwise.

Parameters:

expr - calling expression

cmp - comparator

arg - argument

Returns:

resulting expression

Throws:

QueryException - evaluation exception

atomic

public Bln atomic(QueryContext ctx)
           throws QueryException

Description copied from class: Expr

Evaluates the expression and returns the resulting item or a null reference. If this method is not overwritten, Expr.iter(org.basex.query.QueryContext) must be implemented.

Overrides:

atomic in class Expr

Parameters:

ctx - query context

Returns:

iterator

Throws:

QueryException - query exception

last

public boolean last(QueryContext ctx)

Returns false if no more results can be expected.

Parameters:

ctx - query context

Returns:

result of check

uses

public boolean uses(Expr.Use use,
                    QueryContext ctx)

Description copied from class: Expr

Indicates if an expression uses the specified type. Called by the compiler to perform certain optimizations. true is returned by default and thus assumed as "worst-case".

Overrides:

uses in class Simple

Parameters:

use - use type to be checked

ctx - query context

Returns:

result of check

returned

public Return returned(QueryContext ctx)

Description copied from class: Expr

Indicates the return type of an expression. Called by the compiler to check if expressions can be reformulated. null is returned by default.

Overrides:

returned in class Expr

Parameters:

ctx - query context

Returns:

result of check

toString

public java.lang.String toString()

Specified by:

toString in class ExprInfo

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.

Overrides:

plan in class Simple

Parameters:

ser - serializer

Throws:

java.io.IOException - exception