org.basex.query.util
Class Var

java.lang.Object
  org.basex.query.ExprInfo
      org.basex.query.expr.Expr
          org.basex.query.util.Var

public final class Var
extends Expr

Variable.

Author:

Workgroup DBIS, University of Konstanz 2005-10, ISC License, Christian Gruen

Nested Class Summary

Nested classes/interfaces inherited from class org.basex.query.expr.Expr

Expr.Use

Field Summary

Expr	expr Variable expressions.
boolean	global Global flag.
Item	item Variable results.
QNm	name Variable name.
Return	ret Return type.
SeqType	type Data type.

Constructor Summary

Var(QNm n)
Constructor.

Var(QNm n, boolean g)
Constructor.

Var(QNm n, SeqType t, boolean g)
Constructor.

Method Summary

Var	bind(Expr e, QueryContext ctx) Binds the specified expression to the variable.
Var	bind(Item it, QueryContext ctx) Binds the specified item to the variable.
String	color() Returns a color string for the expression.
Var	comp(QueryContext ctx) Optimizes and compiles the expression.
Var	copy() Returns a copy of the variable.
boolean	eq(Var v) Compares the variables for reference or name equality.
Item	item(QueryContext ctx) Evaluates the variable and returns the resulting item.
Iter	iter(QueryContext ctx) Evaluates the expression and returns an iterator on the resulting items.
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.
String	toString()
boolean	uses(Expr.Use u, QueryContext ctx) Indicates if an expression uses the specified type.
boolean	visible(Var v) Checks if the variable is not shadowed by the specified variable.

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

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

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

Field Detail

ret

public Return ret

Return type.

global

public final boolean global

Global flag.

name

public final QNm name

Variable name.

type

public SeqType type

Data type.

expr

public Expr expr

Variable expressions.

item

public Item item

Variable results.

Constructor Detail

Var

public Var(QNm n)

Constructor.

Parameters:

n - variable name

Var

public Var(QNm n,
           boolean g)

Constructor.

Parameters:

n - variable name

g - global flag

Var

public Var(QNm n,
           SeqType t,
           boolean g)

Constructor.

Parameters:

n - variable name

t - data type

g - global flag

Method Detail

comp

public Var comp(QueryContext ctx)
         throws QueryException

Description copied from class: Expr

Optimizes and compiles the expression.

Specified by:

comp in class Expr

Parameters:

ctx - query context

Returns:

optimized Expression

Throws:

QueryException - query exception

bind

public Var bind(Expr e,
                QueryContext ctx)
         throws QueryException

Binds the specified expression to the variable.

Parameters:

e - expression to be set

ctx - query context

Returns:

self reference

Throws:

QueryException - query exception

bind

public Var bind(Item it,
                QueryContext ctx)
         throws QueryException

Binds the specified item to the variable.

Parameters:

it - item to be set

ctx - query context

Returns:

self reference

Throws:

QueryException - query exception

iter

public Iter iter(QueryContext ctx)
          throws QueryException

Description copied from class: Expr

Evaluates the expression and returns an iterator on the resulting items. If this method is not overwritten, Expr.atomic(org.basex.query.QueryContext) must be implemented.

Overrides:

iter in class Expr

Parameters:

ctx - query context

Returns:

resulting item

Throws:

QueryException - query exception

item

public Item item(QueryContext ctx)
          throws QueryException

Evaluates the variable and returns the resulting item.

Parameters:

ctx - query context

Returns:

iterator

Throws:

QueryException - query exception

eq

public boolean eq(Var v)

Compares the variables for reference or name equality.

Parameters:

v - variable

Returns:

result of check

visible

public boolean visible(Var v)

Checks if the variable is not shadowed by the specified variable.

Parameters:

v - variable

Returns:

result of check

copy

public Var copy()

Returns a copy of the variable.

Returns:

copied variable

uses

public boolean uses(Expr.Use u,
                    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".

Specified by:

uses in class Expr

Parameters:

u - 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

color

public String color()

Description copied from class: ExprInfo

Returns a color string for the expression.

Overrides:

color in class ExprInfo

Returns:

color

plan

public void plan(Serializer ser)
          throws 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:

IOException - I/O exception

toString

public String toString()

Specified by:

toString in class ExprInfo