org.basex.query.xpath.func
Class Func

java.lang.Object
  org.basex.query.xpath.expr.Expr
      org.basex.query.xpath.func.Func

Direct Known Subclasses:

BooleanFunc, Ceiling, Concat, Contains, ContainsLC, Count, Distinct, Doc, False, Floor, Id, Lang, Last, LocalName, Name, NamespaceURI, Nodes, NormalizeSpace, Not, NumFunc, Position, Random, Round, Sort, StartsWith, StringFunc, StringLength, SubStr, SubstringAfter, SubstringBefore, Sum, Translate, True

public abstract class Func
extends Expr

Interface for XPath functions.

Author:

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

Field Summary

java.lang.String

desc Function description.

Constructor Summary

Func(Expr[] arg, java.lang.String dsc)
Function constructor.

Method Summary

abstract boolean	checkArguments() Checks validity/number of arguments.
Expr	compile(XPContext ctx) Tries to optimize the Expression.
Item[]	evalArgs(XPContext ctx) Evaluates the arguments.
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

Field Detail

desc

public final java.lang.String desc

Function description.

Constructor Detail

Func

public Func(Expr[] arg,
            java.lang.String dsc)

Function constructor.

Parameters:

arg - arguments

dsc - expected function pattern

Method Detail

checkArguments

public abstract boolean checkArguments()

Checks validity/number of arguments.

Returns:

result of comparison

compile

public Expr compile(XPContext ctx)
             throws EvalException

Description copied from class: Expr

Tries to optimize the Expression.

Specified by:

compile in class Expr

Parameters:

ctx - expression context

Returns:

optimized Expression

Throws:

EvalException - evaluation exception

evalArgs

public final Item[] evalArgs(XPContext ctx)
                      throws EvalException

Evaluates the arguments.

Parameters:

ctx - query context

Returns:

xpath values

Throws:

EvalException - evaluation exception

toString

public final java.lang.String toString()

Specified by:

toString in class Expr

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