saffron.opt
Class Operand

java.lang.Object
  |
  +--saffron.opt.Operand

All Implemented Interfaces:

Walkable

public class Operand

extends Object

implements Walkable

An Operand determines whether a Rule can be applied to a particular expression.

For example, the rule to pull a filter up from the left side of a join takes operands: (Join (Filter) (Any)).

Note that children means different things if it is empty or it is null: (Join (Filter ()) (Any)) means that, to match the rule, Filter must have no operands.

Field Summary

private Operand[]	children
private Class	clazz
private CallingConvention	convention
(package private) static Operand[]	noOperands
(package private) int	ordinalInParent
(package private) int	ordinalInRule
(package private) Operand	parent
(package private) Rule	rule
(package private) int[]	solveOrder

Constructor Summary

Operand(Class clazz, CallingConvention convention, Operand[] children)
Creates an operand which matches any CallingConvention.

Operand(Class clazz, Operand[] children)
Creates an operand which matches any CallingConvention.

Method Summary

Object[]	getChildren() returns an array of the object's children.
boolean	matches(Rel rel) Returns whether a relational expression matches this operand.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

clazz

private final Class clazz

convention

private final CallingConvention convention

children

private final Operand[] children

parent

Operand parent

ordinalInParent

int ordinalInParent

rule

Rule rule

ordinalInRule

int ordinalInRule

solveOrder

int[] solveOrder

noOperands

static final Operand[] noOperands

Constructor Detail

Operand

public Operand(Class clazz,
               Operand[] children)

Creates an operand which matches any CallingConvention.

Pre-condition:

clazz != null

Operand

public Operand(Class clazz,
               CallingConvention convention,
               Operand[] children)

Creates an operand which matches any CallingConvention.

Pre-condition:

clazz != null

Method Detail

getChildren

public Object[] getChildren()

Description copied from interface: Walkable

returns an array of the object's children. Those which are not Walkable are ignored.

Specified by:

getChildren in interface Walkable

matches

public boolean matches(Rel rel)

Returns whether a relational expression matches this operand. It must be of the right class and calling convention.