Some time ago I had an interesting discussion with Tony Marston. Suddenly I found myself on the middle of what seems to be an ongoing war related to what’s OOP. It seems to (still) be a heated debated on some circles, so I want to share some thoughts on the topic.
So around 1962, 2 guys from Norway (Ole Johan Dahl and Kristen Nygaard) extended the Algol programming language to easily create simulations. They called the new language Simula. The idea was that “A discrete event system is viewed as a collection of processes whose actions and interactions completely describe the operation of the system”. Little did they know that they work would create a revolution in the programming community.
The calm before the storm
Sometime after the invention of Simula, in 1966, a newly graduated from the University of Utah came in contact with it. As he tried to understand the concepts behind this newborn language something made click in his mind. His name was Alan Kay and he was the one who coined the object-oriented programming term. His vision was profound yet simple: a net of interconnected software computing units called objects sending messages to each other. His idea was the software equivalent of the internet. He also had the idea of a network of interconnected computers by either a wired or wireless mean by the way.
Around 1979 a Danish man called Bjarne Stroustrup was working for AT&T Bell Labs, where he had the problem of analyzing the Unix Kernel with respect to distributed computing. The problem was that C was way too low level for a large system. It was then that memories from his Ph.D. thesis, which has been written using Simula, came back. Using Simula as a base, Bjourne extended C to support classes, which he called “C with Classes” and later “C++”.
The smalltalk faction
Smalltalk it’s the brainchild of Alan Kay. It’s the reification of his vision. The language itself it’s pretty compact.
Smalltalk sports a dynamic typing system, that is, the type is not enforced at compile time.
An object is a computing unit that sends and receives messages. The user defines which actions must take place when a given message is received by a specific object. If there’s not action defined for a particular message, then the object notifies the system with a ‘message not understood’ message.
Alan Kay was heavily influenced by LISP. In LISP everything is a list: code, data, everything. This allows powerful metaprogramming techniques. Kay build upon that metaphor: everything in smalltalk is an object. Everything. A number is just an object which knows how to respond to messages like “+ 3”. A string is an object that knows how to respond to messages like “reverse”. Even inline functions/closures are objects (known as blocks) that respond to a “value” message. That’s all there is to it. This is the reason why static typing is unnecessary: you just care whether the object can respond to a message or not.
The C++ camp
C++ was designed with systems creation in mind. As such it deals with stuff like performance and memory footprint. If you are familiar with C, C++ it’s a natural evolution. It can be tricky, however, to get the most out of the object extension. This is due to C++ being a multiparadigm language, meaning that you may still resort to solutions in a different paradigm that could be implemented in a cleaner way using OOP. Stroustrup talked about this in his 1995 OOPSLA paper (see the concrete types section).
It uses a static type system, so the compiler validates every type and related operation.
An object is a structure of data along with methods to manipulate that data. You directly invoke the methods on the object.
Classes are a type extension mechanism, allowing the developer to create a DSL on top of C while still having access to all the lower level features. In order to circumvent some of the problems that arise from a static type system, it introduces templating, which allows a higher reusability.
The eternal bashing warfare
So, the eternal discussion about OOP stems from these 2 schools of thought. To some, OOP is nothing more than procedural programming plus encapsulation, inheritance and polymorphism. To others (myself included) it involves a completely different mindset. The reality is that C++ is indeed an object-oriented extension on top of a procedural language whereas smalltalk is a completely new language that heavily draws from the functional realm. Therefore, the claims from each group are valid depending on the point of view. As someone who learned OOP using C++ I have found very beneficial to learn smalltalk later. Really, having nothing else than objects to work, helped me understand the boundaries between OOP and Procedural programming, helping me shape my approach to OOP design and decomposition.
Peace to the world
So, whether you belong to the smalltalk or the C++ party, remember to be tolerant to other people point of view. It’s an absolute benefit to learn to see from another perspective. So next time you find yourself on another OOP battle camp remember that the ultimate value comes from learning to work together, despite differences, than to demonstrate that you’re right and everybody else is not.