lights.interfaces
Interface IField

All Known Implementing Classes:

Field, Field

public interface IField

Represents a single typed field of a tuple. The type of a field can be any class implementing the Serializable interface. A field can either contain a value, or be characterized just by its type. In Linda jargon, the former is called an actual field, while the latter is called a formal field. Tuples with formals are typically used as a template to query the tuple space by pattern matching. Different matching rules can be implemented by redefining the matches method.

Formals and actuals are set by using two separate methods, setToFormal and setToActual. null is a legal value for the domain on which the type of the field is defined, thus fields whose value is null are considered to be actuals. Nevertheless, the null value must be specified by using a special method setToNullActual. Had the null value been set using setToActual(null), it would have been impossible to determine the type of the actual. Hence, null fields should not be considered as formals by the classes implementing this interface.

Version:

1.0

Author:

Gian Pietro Picco

Method Summary

java.lang.Class	getType() Returns the type of this field.
java.io.Serializable	getValue() Returns the value of this field.
boolean	isFormal() Returns true if the field is a formal, false otherwise.
boolean	matches(IField field) Determines the rule used for pattern matching between fields.
IField	set(IField field) Substitutes this field with the one passed as a parameter.
IField	setToActual(java.io.Serializable obj) Sets the value of this field to the object passed as a parameter.
IField	setToFormal(java.lang.Class classObj) Sets this field to be a formal whose type becomes the class passed as a parameter.
IField	setToNullActual(java.lang.Class classObj) Sets the value of this field to null.

Method Detail

set

public IField set(IField field)

Substitutes this field with the one passed as a parameter. If field is a formal, this field becomes a formal with field's type. If field is an actual, this fields becomes an actual with the type and value of field.

Parameters:

field - the field to be assigned.

Returns:

the resulting field.

getValue

public java.io.Serializable getValue()

Returns the value of this field.

getType

public java.lang.Class getType()

Returns the type of this field.

setToActual

public IField setToActual(java.io.Serializable obj)

Sets the value of this field to the object passed as a parameter. The type of the field is set automatically to the one of the object.

Parameters:

obj - the new value of the field.

Returns:

the resulting field.

setToNullActual

public IField setToNullActual(java.lang.Class classObj)

Sets the value of this field to null. The type of the field is set to the class passed as a parameter.

Parameters:

classObj - the class to be associated to the null actual.

Returns:

the resulting field.

setToFormal

public IField setToFormal(java.lang.Class classObj)

Sets this field to be a formal whose type becomes the class passed as a parameter.

Parameters:

classObj - the new type of this field.

Returns:

the resulting field.

isFormal

public boolean isFormal()

Returns true if the field is a formal, false otherwise.

matches

public boolean matches(IField field)

Determines the rule used for pattern matching between fields. Classes implementing this interface may specify different policies for matching.

Returns:

true if the field passed as a parameter matches this field, false otherwise.