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Features

classes several upper classes, a list of slots (member variables in C + + / Java) and a meta special class. Slots can be assigned per class (all instances of a class share the slot) or, for example. Each property has a name and the value of a house can be addressed by name to SLOT-VALUE function. In addition, specific functions are defined to write generic or read the values of slots in charge. Every apartment in a CLOS class should have a unique name.

CLOS is a multiple system of distribution. This means that methods can in some or all of their required arguments are specialized. The most OO languages are a program so that the methods that are specialized to the first argument means. Another characteristic is that the methods “are” not classes, the classes offer no namespace for generic functions or methods. Methods are defined separately from classes, and they have no special access (such as self-employed or protected) class slots.

Methods

CLOS are grouped into generic functions. A generic function is an object that acts as a function that a number of methods, with a share name and argument structure, which can be combined each called for different arguments. Since Common Lisp provides classes for non-CLOS structures and built-in data types (numbers, strings, characters, symbols …), CLOS dispatch also works with non-CLOS classes. CLOS supports the expedition to the individual objects (eql specialized households). CLOS only through the support of the distribution by default on all types of common data Lisp (eg article introduced not work for array types or very specific types of Deftype). However, most implementations of Common Lisp, a protocol meta-object, the generic functions, application-specific specialization and distribution rules

Expedition CLOS, allows to offer different than most OO languages.

A list of arguments as a list of applicable methods is determined.

This list according to their specific specialized households parameter is sorted.

The most effective method is then called with the original arguments.

These shipping operation of the mechanism at run time. Adding or removing methods can change in effective methods (even if the generic function called with the same arguments) to run. Change the combination method can also lead to different effective methods

For example

;. Declare the prototype argument structure common

(defgeneric f (xy))

; define an implementation for (integer TF), where t all types

(defmethod f ((integer x) y) 1)

(f 1 2.0) => 1 <

/ p>; define an implementation for (real number f) > p (defmethod f ((integer x) (y real)) 2 )

2 and sending changed As in most dynamic languages, CLOS does not enforce encapsulation. Each slot can be the function slot-value or access methods (possibly even created). To access the site via the value you need to know the name of the slot. CL programmers use to explain the facilities of the language pack, which functions or data structures for export

Are Apart from the normal use (“primary”) methods, there are. Front: Little by: the methods. These change the order in which the methods are executed in a derived class. A: about method can indicate whether the primary method is executed at all. In addition, the programmer can specify that all methods are called possible along the primary class hierarchy, or only one, offers the next.

The standard method of grouping countries on the primary, before, after and around methods. There are other combinations with the standard method by using another method. New types (simple and complex) method combination and method can be defined.

CLOS allows multiple inheritance. If the default command, in which the methods are executed in multiple inheritance is not correct, the programmer can the problems of inheritance diamond indicating the order of method combinations.

CLOS is dynamic, meaning that not only the content but also the structure of objects can be changed at run time. CLOS supports changing class definitions on the fly (although instances of the class in question is already there) and change the participants in a particular instance of the operator-class change.. CLOS allows add, delete and redefine methods Running time

CLOS is not a language prototype. classes must be defined before objects can be

Outside of ANSI Common Lisp, it is a widely implemented extension CLOS called Meta-Object Protocol (MOP). The MOP defines a standard interface for the foundations of the CLOS implementation, the processing of classes, sub-descriptions, generic functions and methods, as instances of metaclasses and allows the definition of new metaclasses and modifying all practices CLOS. The flexibility of the CLOS MOP anticipates aspect-oriented programming, defined later by some of the same engineers, was developed as Gregor Kiczales. The MOP, the behavior of the entire object that a number of protocols. In terms of CLOS defined. It is possible, a new object systems provided by the extension or modification of the functionality to create CLOS. The book The art of metaobject protocol describes the use and implementation

CLOS MOP.

implementation of various Common Lisp have slightly different support for the Meta-Object Protocol. The Closer project aims to provide the missing features.

more influences on Lisp Object System is based

Gourmet

(and its successor, new flavors) was the topic that was Lisp machine at the MIT. Most of the Lisp Machine operating systems and many applications for the use or flavors of new flavors. Flavors introduced multiple inheritance and mixins among other features. Flavors is almost superfluous, although common, there are Lisp implementations . Gourmet was using the messaging paradigm. New Flavors provides generic functions.

common loops the successor of loops (Xerox InterLisp-D) was. common loops implemented for Common Lisp. A portable implementation called Portable Common Loops (PCL) was the first implementation of CLOS. PCL is widely violated and continues to be the basis for the implementation of several CLOS Common Lisp implementations provide. PCL is implemented primarily in portable Common Lisp, with only a few stressful.

References

^

CLOS is a standard supply. CLOS multiple vendors. CLOS (or any part thereof) is used to add object orientation to other dialects of Lisp or Emacs Lisp as EULISP “PG 110 of Veitch 1998

^ Project Closer : Closer to MOP

“common loops. merging Lisp and object-oriented programming” by Daniel G. Bobrow, Kenneth Kahn, Gregor Kiczales, Larry Masinter, Mark Stefik, Frank Zdybel. 1986, Portland, Oregon, USA. Pages 17 to 29 of the Conference on Object Oriented Programming Systems Languages and Applications, ISSN 0362-1340

“History and Description of the Clos” by Jim Veitch .. Pages 107-158 Handbook of Programming Languages, Volume IV: Functional programming languages and logic, ed. Peter H. Salus. 1998 (1st edition), Macmillan Publishing ISBN 1-57870-011-6 technical

literature

Gregor Kiczales, Jim and Daniel G. Bobrow of Rivières, The art of metaobject protocol, 1991, MIT Press. ISBN 0-262-61074-4

The Common Lisp Object System: An Overview by Richard P. Gabriel and Linda DeMichiel is a good introduction into the motivation for the definition of classes by generic features Rules

ENDED Nick Levine explains step by step, contact with the implementation of OO concepts in CLOS, and how to use them. It is for anyone with a basic knowledge of Lisp or Scheme

Sonya Keene, Object-oriented programming in Common Lisp. Programmer’s Guide to CLOS, 1988, Addison-Wesley. ISBN 0-201-17589-4

Common Lisp hyperspectral, Chapter 7: Objects

Categories: Common Lisp | Object Oriented Programming

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