DOCSLIB.ORG

Object-Oriented Programming Support for CLASSIC

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Object-Oriented Programming Support for CLASSIC From: AAAI Technical Report WS-96-05. Compilation copyright © 1996, AAAI (www.aaai.org). All rights reserved. Object-Oriented ProgrammingSupport for CLASSIC Ralf M~iller University of Hamburg,Computer Science Department Vogt-KOlln-Str.30, D-22527Hamburg, Germany moeller@in formatik,uni-hamburg, de Abstract:The main thesis of this paperis that in order to tional programmingpoint of view it is irrelevant useDescription Logics in practical applications, a seamless whether a result of a function call is defined by integration with object-oriented systemdevelopment meth- merely looking up a set of instances in a relation odologiesmust be realized. It presents an object-oriented table or by actually computinginstances with com- programminglayer for CLASSIC. plex algorithms and auxiliary data structures. Sec- 1. Introduction ond, using genetic accesser functions for retrieving the objects that are directly set into relation to a spe- Althoughthe logical semantics of Description Logics cific individual allows a lot of error checkingcode to (DL)modeling constructs is a big plus, to ensure deci- be automatically generated. A unified interface for dability of the subsumptionproblem, the expressive- accessing the services that an object provides hides ness of the logical language must be limited. The manyrepresentation details whichare irrelevant from consequenceis that in a real application without toy a moreabstract perspective. problems, currently not all aspects can be formally modeled with DL constructs. This means that pro- For example,in a graphical user interface, the draw- grammingis still necessary. As a DL we use the ing function for an object might depend on the CLASSICsystem [9]. Reducing CLASSICto practice object’s concepts. User interface programmingis one [1] means that the DL can be integrated into the of the best examplesfor the application of object-ori- whole system development approach which, at the ented programmingtechniques. For rapid user inter- current state of the art, uses object-oriented modeling. face development however, an existing UIMSmust In this paper, the CLOSOOP perspective will be used be reused. UIMSsprovide powerful programming [10]. Thepaper presents an object-oriented programming abstractions which are modeledwith the object-ori- layer for CLASSIC.It assumes basic knowledgeabout ented representation techniques (e.g. for CLOSthe CLOS1 [3]. UIMSCLIM might be used [7]). There is no way to rebuild these software libraries with CLASSICor The integration of CLASSICand CLOSrequires that any other DLin a reasonable time. So what can be genetic functions and methods can be written for done? Copying information associated with a DL CLASSICindividuals. The procedural parts of an object into a CLOSobject which is used for UI part application should be able to use CLASSICindividu- of an application is inadequate as well. Unfortu- als just like CLOSinstances. The "services" of an nately, managing multiple "copies" of the same object are accessed only by the use of generic func- object is a direct contradiction to the principles of tions. This meansthat the relational part of CLASSIC object-otiented programming.Thus, for rapid appli- should be hidden behind a functional layer because, cation development, object-oriented programming from a software engineering point of view, dealing techniques must be made available to CLASSICindi- with individuals and relations earl be quite cumber- viduals. The next chapter discusses an approach that somefor at least two reasons: First of all, froma func- demonstrates how this can be achieved with an extension to CLASSICthat uses CLOS-like genetic 1. Thispaper is a shortenedand rewritten version of a paperpre- functions to access information about an individual. sentedat OOPSLA’96[5]. Theextensions for the CLASSICsys- It will be shownthat the implementation of CLAS- tempresented in this paperare availablefrom the author[6]. SIC methoddispatch can be surprisingly simple. - 170- 2. Integrating OOP and DL ated. If they do not already exist, corresponding generic2 functions are automatically generated. Generic functions for Description Logics have also been developed in the LoomSystem [2]. Methoddis- The first role option :single-value-p specifies patch for individuals is provided by specific genetic whether a single value or a set of values should be functions which dispatch on ABoxobjects but not on returned by the role reader function. The other option CLOSobjects. Loomalso supports CLOSclasses for :error-if-null is used to insert code for error the implementation of ABoxindividuals but only a checking to avoid an empty set to be returned. The limited sort of reasoning is implemented on these following example illustrates the use of define- instances (no dynamic reclassification by forward accessor. For concept and role declarations the inferences). KRSSsyntax is used [8]. (define-primitive-conceptship classic-thing) Theapproach presented in this paper clearly separates (define-primitive-rolehas-position-x nil) CLASSICand CLOSbut provides a unified way to (define-primitive-rolehas-position-y nil) access the services of both systems. (define-accessorsship (has-position-xposition-x : single-value-pt 2.1. Accessors: A Functional Interface to a :error-if-nullt) Knowledge Base (has-position-yposition-y CLASSICitself provides a relational interface for : single-value-pt :error-if-nullt) retrieving and adding role fillers. Givenan individual and a role, the set of fillers can be retrieved: (cl- As in CLOS,for accessing information of an object, fillers<ind> <role>). In manycases only one define-accessors defines methods for generic filler is returned. However,the result will alwaysbe a functions. Additional methods might be written by set (actually a list) and the function first must the programmer(e.g. around methods or after and applied to get the list element itself. To hide the before methods). CLASSICindividuals require repeating access to the first element, an additional another dispatch mechanismwhich is realized by extended generic functions. function will have to be written. Furthermore,in some circumstances,it will be considered as an error if the 2.2. Generic Functions and Methods filler is not known. Unfortunately, additional code mustbe written to checkthis. If nil (the emptyset) The extended generic functions presented in this returned, an error is likely to occur in subsequent paper can dispatch on CLASSICconcepts or CLOS function calls whenan individual is expected. Again, classes or both. The form define-generic- func- code must be written to avoid this. Instead of writing tion is used to define a generic function with dis- this code manually, a more general mechanismis patching extended to CLASSICindividuals. advantageous. The way to access individuals should The argument list of define-generic-function be declaratively defined using generic functions and indicates which arguments expect CLASSICdispatch corresponding low-level code for methods should be and which arguments use standard CLOSdispatch. automatically generated. The declaration form (define-generic-function<function-name> define- acces sors has been introduced to specify (<dispatched-argument-description>... the access to individuals in that way. [ <other-argument>... ] ) [ <option>...] ) (define-accessors<concept-name> (<role-name><accessor- name> A description for a dispatching argumentis a list con- [ :single-value-p<boolean> ] sisting of an argumentname and a dispatch indicator [ :error-lf-null<boolean> ] ) ...) For each role description mentionedafter the concept 2. The explicit declaration of a generic aeeessor function is nee- name, a reader method and a serf writer method for essary, for instance, whena special methodcombination that dif- the generic function <accessor-name> is gener- fers from the standard methodcombination is to be used [10]. - 171- (either :clos or :classic). Just as defgeneric function can be defined as follows (comparethis to from CLOS,define-generic-function alSO sup- initialize- instance from CLOS). ports ordinary argumentswithout specializer (called (define-methodinitialize-individual :after other-arguments). The optionsfor define- ((ind <concept-name>)&rest initargs) generic-function are the same as for defge- ., ,) neric.Note that method combinations are also sup- Initialization arguments can also be given to cre- ported. ate-individual.The list of "initargs" is a sequenceof rolenames and corresponding setsof ini- Methodscan be definedwith the form define- tialfillers) method. (define-method<function-name> [ <qualifier> 2.4. Computation of the Concept Precedence ( <dispatched-argument>... [ <other-argument>... ] ) List ¯ 0 0 ) The TBoxdefines a partial order relation between The syntax of a dispatched argument in a method concepts (subsumption relation). In order to define parameter list is identical to the syntax of arguments howmethod dispatch is handled, the multiple inherit- for defmethod of CLOS. The <qualifier> indi- ance lattice must be serialized by a concept prece- cates the kind of methodcombination. In addition to dence list which represents a total order between names for CLOSclasses, CLASSICconcept names concepts. A concept precedence list is used for the can be used as specializers. same purposes as a CLOSclass precedence list, it The following declarations continue the example defines howan effective methodfor a specific func- from above. tion call is computed(see the detailed introduction in (define-generic-functionpos ( (ship :classic) [3]). A valid
Load more

Recommended publications
  • Metaobject Protocols: Why We Want Them and What Else They Can Do
    Metaobject protocols: Why we want them and what else they can do Gregor Kiczales, J.Michael Ashley, Luis Rodriguez, Amin Vahdat, and Daniel G. Bobrow Published in A. Paepcke, editor, Object-Oriented Programming: The CLOS Perspective, pages 101 ¾ 118. The MIT Press, Cambridge, MA, 1993. © Massachusetts Institute of Technology All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means (including photocopying, recording, or information storage and retrieval) without permission in writing from the publisher. Metaob ject Proto cols WhyWeWant Them and What Else They Can Do App ears in Object OrientedProgramming: The CLOS Perspective c Copyright 1993 MIT Press Gregor Kiczales, J. Michael Ashley, Luis Ro driguez, Amin Vahdat and Daniel G. Bobrow Original ly conceivedasaneat idea that could help solve problems in the design and implementation of CLOS, the metaobject protocol framework now appears to have applicability to a wide range of problems that come up in high-level languages. This chapter sketches this wider potential, by drawing an analogy to ordinary language design, by presenting some early design principles, and by presenting an overview of three new metaobject protcols we have designed that, respectively, control the semantics of Scheme, the compilation of Scheme, and the static paral lelization of Scheme programs. Intro duction The CLOS Metaob ject Proto col MOP was motivated by the tension b etween, what at the time, seemed liketwo con icting desires. The rst was to have a relatively small but p owerful language for doing ob ject-oriented programming in Lisp. The second was to satisfy what seemed to b e a large numb er of user demands, including: compatibility with previous languages, p erformance compara- ble to or b etter than previous implementations and extensibility to allow further exp erimentation with ob ject-oriented concepts see Chapter 2 for examples of directions in which ob ject-oriented techniques might b e pushed.
    [Show full text]
  • Towards Practical Runtime Type Instantiation
    Towards Practical Runtime Type Instantiation Karl Naden Carnegie Mellon University [email protected] Abstract 2. Dispatch Problem Statement Symmetric multiple dispatch, generic functions, and variant type In contrast with traditional dynamic dispatch, the runtime of a lan- parameters are powerful language features that have been shown guage with multiple dispatch cannot necessarily use any static in- to aid in modular and extensible library design. However, when formation about the call site provided by the typechecker. It must symmetric dispatch is applied to generic functions, type parameters check if there exists a more specific function declaration than the may have to be instantiated as a part of dispatch. Adding variant one statically chosen that has the same name and is applicable to generics increases the complexity of type instantiation, potentially the runtime types of the provided arguments. The process for deter- making it prohibitively expensive. We present a syntactic restriction mining when a function declaration is more specific than another is on generic functions and an algorithm designed and implemented for laid out in [4]. A fully instantiated function declaration is applicable the Fortress programming language that simplifies the computation if the runtime types of the arguments are subtypes of the declared required at runtime when these features are combined. parameter types. To show applicability for a generic function we need to find an instantiation that witnesses the applicability and the type safety of the function call so that it can be used by the code. Formally, given 1. Introduction 1. a function signature f X <: τX (y : τy): τr, J K Symmetric multiple dispatch brings with it several benefits for 2.
    [Show full text]
  • Balancing the Eulisp Metaobject Protocol
    Balancing the EuLisp Metaob ject Proto col x y x z Harry Bretthauer and Harley Davis and Jurgen Kopp and Keith Playford x German National Research Center for Computer Science GMD PO Box W Sankt Augustin FRG y ILOG SA avenue Gallieni Gentilly France z Department of Mathematical Sciences University of Bath Bath BA AY UK techniques which can b e used to solve them Op en questions Abstract and unsolved problems are presented to direct future work The challenge for the metaob ject proto col designer is to bal One of the main problems is to nd a b etter balance ance the conicting demands of eciency simplicity and b etween expressiveness and ease of use on the one hand extensibili ty It is imp ossible to know all desired extensions and eciency on the other in advance some of them will require greater functionality Since the authors of this pap er and other memb ers while others require greater eciency In addition the pro of the EuLisp committee have b een engaged in the design to col itself must b e suciently simple that it can b e fully and implementation of an ob ject system with a metaob ject do cumented and understo o d by those who need to use it proto col for EuLisp Padget and Nuyens intended This pap er presents a metaob ject proto col for EuLisp to correct some of the p erceived aws in CLOS to sim which provides expressiveness by a multileveled proto col plify it without losing any of its p ower and to provide the and achieves eciency by static semantics for predened means to more easily implement it eciently The current metaob
    [Show full text]
  • OOD and C++ Section 5: Templates
    Templates - Generic Programming Decide which algorithms you want: parameterize them so that they work for OOD and C++ a wide-range of types & data structures Section 5: Templates Templates in C++ support generic progarmming Templates provide: •simple way to represent general concepts •simple way to combine concepts Use ‘data-types’ as parameters at compilation Advantage: • more general ‘generic code’ • reuse same code for different data types • less bugs - only implement/debug one piece of code • no overhead on run-time efficiency compared to data specific code Use of Templates Templates in C++ Make the definition of your class as broad as possible! template class declaration: mytemplate.hh template <class DataC> class mytemplate { public: Widely used for container classes: mytemplate(); • Storage independent of data type void function(); • C++ Standard Template Library (Arrays,Lists,…..) protected: int protected_function(); Encapsulation: private: Hide a sophisticated implementation behind a simple double private_data; interface }; template <class DataC>: • specifies a template is being declared • type parameter ‘DataC’ (generic class) will be used • DataC can be any type name: class, built in type, typedef • DataC must contain data/member functions which are used in template implementation. Example - Generic Array Example - Generic Array (cont’d) simple_array.hh template<class DataC> class simple_array { private: #include “simple_array.hh” int size; DataC *array; #include “string.hh” public: void myprogram(){ simple_array(int s); simple_array<int> intarray(100); ~simple_array(); simple_array<double> doublearray(200); DataC& operator[](int i); simple_array<StringC> stringarray(500); }; for (int i(0); i<100; i++) template<class DataC> intarray[i] = i*10; simple_array<DataC>::simple_array(int s) : size(s) { array = new DataC[size]; } // & the rest….
    [Show full text]
  • Julia: a Modern Language for Modern ML
    Julia: A modern language for modern ML Dr. Viral Shah and Dr. Simon Byrne www.juliacomputing.com What we do: Modernize Technical Computing Today’s technical computing landscape: • Develop new learning algorithms • Run them in parallel on large datasets • Leverage accelerators like GPUs, Xeon Phis • Embed into intelligent products “Business as usual” will simply not do! General Micro-benchmarks: Julia performs almost as fast as C • 10X faster than Python • 100X faster than R & MATLAB Performance benchmark relative to C. A value of 1 means as fast as C. Lower values are better. A real application: Gillespie simulations in systems biology 745x faster than R • Gillespie simulations are used in the field of drug discovery. • Also used for simulations of epidemiological models to study disease propagation • Julia package (Gillespie.jl) is the state of the art in Gillespie simulations • https://github.com/openjournals/joss- papers/blob/master/joss.00042/10.21105.joss.00042.pdf Implementation Time per simulation (ms) R (GillespieSSA) 894.25 R (handcoded) 1087.94 Rcpp (handcoded) 1.31 Julia (Gillespie.jl) 3.99 Julia (Gillespie.jl, passing object) 1.78 Julia (handcoded) 1.2 Those who convert ideas to products fastest will win Computer Quants develop Scientists prepare algorithms The last 25 years for production (Python, R, SAS, DEPLOY (C++, C#, Java) Matlab) Quants and Computer Compress the Scientists DEPLOY innovation cycle collaborate on one platform - JULIA with Julia Julia offers competitive advantages to its users Julia is poised to become one of the Thank you for Julia. Yo u ' v e k i n d l ed leading tools deployed by developers serious excitement.
    [Show full text]
  • Genericity Vs Inheritance
    s Genericity Versus Inheritance Bertrand Meyer Interactive Software Engineering, Inc., 270 Storke Road, Suite #7, Goleta CA 93117 ABSTRACT with which a software system may be changed to account for modifications of its requirements), reus­ Genericity, as in Ada or ML, and inheritance, as in ability (the ability of a system to be reused, in whole object-oriented languages, are two alternative tech­ or in parts, for the construction of new systems), and niques for ensuring better extendibility, reusability, compatibility (the ease of combining a system with and compatibility of software components. This ar­ others). ticle is a comparative analysis of these two methods. Good answers to these issues are not purely It studies their similarities and differences and as­ technical, but must include economical and mana­ sesses to what extent each may be simulated in a gerial components as well; and their technical as­ language offering only the other. It shows what fea­ pects extend beyond programming language fea­ tures are needed to successfully combine the two ap­ tures' to such obviously relevant concerns as proaches in an object-oriented language that also fea­ specification and design techniques. It would be wrong, tures strong type checking. The discussion introduces however, to underestimate the technical aspects and, the principal aspects of the language EiffePM whose among these, the role played by proper programming design, resulting in part from this study, includes language features: any acceptable solution must in multiple inheritance and a limited form of genericity the end be expressible in terms of programs, and under full static typing. programming languages fundamentally shape the software designers' way of thinking.
    [Show full text]
  • Object Oriented Programming
    Object oriented programming ✔ The main ideas behind object-oriented programming: ✗ the same type of action may be carried out differently on different types of objects • cutting a cake is different from cutting cloth • driving a car is different from driving a bicycle ✗ however, a type of action may involve similar subactions when carried out on similar objects • mailing a letter involves many of the same moves as mailing a postcard • eating at a French restaurant involves many of the same procedures as eating at a Chinese restaurant ✗ a useful way of describing similarities among objects is by describing their place in an object type hierarchy • a Chinese restaurant is a type of Asian restaurant, which is a type of restaurant, which is a type of retail food outlet, which is a type of retail outlet, which is a type of business, ... ✔ So, think about procedures in relation to a hierarchy of object types LANGUAGES FOR AI Page 1 of 14 LEC 9 Object oriented programming ✔ There are two kinds of object-oriented programming perspectives ✗ message-passing systems: “object oriented perspective” • in a message passing system, messages are sent to objects • what happens depends on what the message is, and what type the object is • each object type “knows” what to do (what method to apply) with each message (send starship-1 ‘move-to-andromeda) ✗ generic function systems: “data-driven perspective” • in a generic function system, objects are passed as arguments to generic functions • what happens depends on what the function is, and what type the object is • each generic function “knows” what to do (what method to apply) with each object type (move-to-andromeda starship-1) ✔ The Common LISP Object System is a generic function system LANGUAGES FOR AI Page 2 of 14 LEC 9 The Common LISP Object System (CLOS) ✔ CLOS classes are similar to LISP structure types..
    [Show full text]
  • Commonloops Merging Lisp and Object-Oriented Programming Daniel G
    CommonLoops Merging Lisp and Object-Oriented Programming Daniel G. Bobrow, Kenneth Kahn, Gregor Kiczales, Larry Masinter, Mark Stefik, and Frank Zdybel Xerox Palo Alto Research Center Palo Alto, California 94304 CommonLoops blends object-oriented programming Within the procedure-oriented paradigm, Lisp smoothly and tightly with the procedure-oriented provides an important approach for factoring design of Lisp. Functions and methods are combined programs that is'different from common practice in in a more general abstraction. Message passing is object-oriented programming. In this paper we inuoked via normal Lisp function call. Methods are present the linguistic mechanisms that we have viewed as partial descriptions of procedures. Lisp data developed for integrating these styles. We argue that types are integrated with object classes. With these the unification results in something greater than the integrations, it is easy to incrementally move a program sum of the parts, that is, that the mechanisms needed between the procedure and object -oriented styles. for integrating object-oriented and procedure-oriented approaches give CommonLoops surprising strength. One of the most important properties of CommonLoops is its extenswe use of meta-objects. We discuss three We describe a smooth integration of these ideas that kinds of meta-objects: objects for classes, objects for can work efficiently in Lisp systems implemented on a methods, and objects for discriminators. We argue that wide variety of machines. We chose the Common Lisp these meta-objects make practical both efficient dialect as a base on which to bui|d CommonLoops (a implementation and experimentation with new ideas Common Lisp Object-Oriented Programming System).
    [Show full text]
  • Generic Programming in OCAML
    Generic Programming in OCAML Florent Balestrieri Michel Mauny ENSTA-ParisTech, Université Paris-Saclay Inria Paris [email protected] [email protected] We present a library for generic programming in OCAML, adapting some techniques borrowed from other functional languages. The library makes use of three recent additions to OCAML: generalised abstract datatypes are essential to reflect types, extensible variants allow this reflection to be open for new additions, and extension points provide syntactic sugar and generate boiler plate code that simplify the use of the library. The building blocks of the library can be used to support many approachesto generic programmingthrough the concept of view. Generic traversals are implemented on top of the library and provide powerful combinators to write concise definitions of recursive functions over complex tree types. Our case study is a type-safe deserialisation function that respects type abstraction. 1 Introduction Typed functional programming languages come with rich type systems guaranteeing strong safety prop- erties for the programs. However, the restrictions imposed by types, necessary to banish wrong programs, may prevent us from generalizing over some particular programming patterns, thus leading to boilerplate code and duplicated logic. Generic programming allows us to recover the loss of flexibility by adding an extra expressive layer to the language. The purpose of this article is to describe the user interface and explain the implementation of a generic programming library1 for the language OCAML. We illustrate its usefulness with an implementation of a type-safe deserialisation function. 1.1 A Motivating Example Algebraic datatypes are very suitable for capturing structured data, in particular trees.
    [Show full text]
  • Lect. 15: Object-Oriented Programming in R
    lect15 http://127.0.0.1:8000/lect15.html Lect. 15: Object-oriented programming in R STAT598z: Intro. to computing for statistics Vinayak Rao Department of Statistics, Purdue University In [ ]: options(repr.plot.width=5, repr.plot.height=3) functions: an abstraction to encourage modular code: Reusables block of code Define operations to apply to any input Object-oriented programming is another kind of abstraction Object-oriented programming is another kind of abstraction: Encapsulation: Pack data and functions into classes Polymorphism: Same functions act differently across classes Inheritence: Write child classes without copying parent classes Components of OOP: Classes: A template for an object (e.g. purdue ) Defines ‘properties’ of objects (e.g. name, puid ) Objects An instance of a class (e.g. varao ) Values assigned to properties ( name = ‘vinayak’ ) Methods Functions aware of properties of the object (e.g. isFaculty() ) Why object oriented programming (OOP)? 1 of 5 3/19/19, 12:08 AM lect15 http://127.0.0.1:8000/lect15.html 1) Useful to group variables together An object is basically a list, with the class attribute set A constructor creates objects of a class In [ ]: new_purdue <- function(name, puid, employee ) { obj <- list(name = name, puid = puid, employee = employee) class(obj) <- 'purdue'; return(obj) } varao <- new_purdue('Vinayak', 1234, 'faculty' ) print(varao) Why object oriented programming (OOP)? 2) Tying methods to objects: Increase capability of software without increasing complexity for user (Chambers): e.g. print vs printMatrix
    [Show full text]
  • Common Lisp Object System
    Common Lisp Object System by Linda G. DeMichiel and Richard P. Gabriel Lucid, Inc. 707 Laurel Street Menlo Park, California 94025 (415)329-8400 [email protected] [email protected] with Major Contributions by Daniel Bobrow, Gregor Kiczales, and David Moon Abstract The Common Lisp Object System is an object-oriented system that is based on the concepts of generic functions, multiple inheritance, and method combination. All objects in the Object System are instances of classes that form an extension to the Common Lisp type system. The Common Lisp Object System is based on a meta-object protocol that renders it possible to alter the fundamental structure of the Object System itself. The Common Lisp Object System has been proposed as a standard for ANSI Common Lisp and has been tentatively endorsed by X3J13. Common Lisp Object System by Linda G. DeMichiel and Richard P. Gabriel with Major Contributions by Daniel Bobrow, Gregor Kiczales, and David Moon 1. History of the Common Lisp Object System The Common Lisp Object System is an object-oriented programming paradigm de- signed for Common Lisp. Over a period of eight months a group of five people, one from Symbolics and two each from Lucid and Xerox, took the best ideas from CommonLoops and Flavors, and combined them into a new object-oriented paradigm for Common Lisp. This combination is not simply a union: It is a new paradigm that is similar in its outward appearances to CommonLoops and Flavors, and it has been given a firmer underlying semantic basis. The Common Lisp Object System has been proposed as a standard for ANSI Common Lisp and has been tentatively endorsed by X3J13.
    [Show full text]
  • Multiple Dispatch and Roles in OO Languages: Ficklemr
    Multiple Dispatch and Roles in OO Languages: FickleMR Submitted By: Asim Anand Sinha [email protected] Supervised By: Sophia Drossopoulou [email protected] Department of Computing IMPERIAL COLLEGE LONDON MSc Project Report 2005 September 13, 2005 Abstract Object-Oriented Programming methodology has been widely accepted because it allows easy modelling of real world concepts. The aim of research in object-oriented languages has been to extend its features to bring it as close as possible to the real world. In this project, we aim to add the concepts of multiple dispatch and first-class relationships to a statically typed, class based langauges to make them more expressive. We use Fickle||as our base language and extend its features in FickleMR . Fickle||is a statically typed language with support for object reclassification, it allows objects to change their class dynamically. We study the impact of introducing multiple dispatch and roles in FickleMR . Novel idea of relationship reclassification and more flexible multiple dispatch algorithm are most interesting. We take a formal approach and give a static type system and operational semantics for language constructs. Acknowledgements I would like to take this opportunity to express my heartful gratitude to DR. SOPHIA DROSSOPOULOU for her guidance and motivation throughout this project. I would also like to thank ALEX BUCKLEY for his time, patience and brilliant guidance in the abscence of my supervisor. 1 Contents 1 Introduction 5 2 Background 8 2.1 Theory of Objects . 8 2.2 Single and Double Dispatch . 10 2.3 Multiple Dispatch . 12 2.3.1 Challenges in Implementation .
    [Show full text]