org.basex.query.xquery.expr
Class Expr

java.lang.Object
  org.basex.query.ExprInfo
      org.basex.query.xquery.expr.Expr

Direct Known Subclasses:

Arr, Context, ForLet, FTExpr, Fun, Item, Root, Single, VarCall

public abstract class Expr
extends ExprInfo

Abstract Expression.

Author:

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

Nested Class Summary

static class	Expr.Return Return types, evaluated by the compiler.
static class	Expr.Using Used types, evaluated by the compiler.

Constructor Summary

Expr()

Method Summary

abstract Expr	comp(XQContext ctx) Optimizes and compiles the expression.
boolean	e() Returns if this is an empty sequence.
boolean	i() Checks if this is an item.
abstract Iter	iter(XQContext ctx) Evaluates the expression and returns an iterator on the resulting items.
Type	returned() Indicates if an expression returns the specified type.
boolean	uses(Expr.Using use) Indicates if an expression uses the specified type.

Methods inherited from class org.basex.query.ExprInfo

color, info, name, plan, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

Expr

public Expr()

Method Detail

comp

public abstract Expr comp(XQContext ctx)
                   throws XQException

Optimizes and compiles the expression.

Parameters:

ctx - query context

Returns:

optimized Expression

Throws:

XQException - evaluation exception

iter

public abstract Iter iter(XQContext ctx)
                   throws XQException

Evaluates the expression and returns an iterator on the resulting items.

Parameters:

ctx - query context

Returns:

resulting item

Throws:

XQException - evaluation exception

i

public boolean i()

Checks if this is an item.

Returns:

result of check

e

public final boolean e()

Returns if this is an empty sequence.

Returns:

result of check

uses

public boolean uses(Expr.Using use)

Indicates if an expression uses the specified type. Called by the compiler to check if expressions can be reformulated. true is returned by default.

Parameters:

use - using flag

Returns:

result of check

returned

public Type returned()

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

Returns:

result of check