As Bjarne Stroustrup points out, "C++ is a multi-paradigmed language." It supports many different styles of programs, or paradigms, and object-oriented programming is only one of these. Some of the others are structured programming and generic programming.
And as Thomas Becker explains in this interesting article, there’s a tension between generic programming and OOP. And here’s the opinion of Alexander Stepanov, an elder statesman of C++, about OOP, from that article:
Let us start with a little trivia quiz. Who said the following things about object-oriented programming?
"I find OOP technically unsound."
"I find OOP philosophically unsound."
"I find OOP methodologically wrong."
"I have yet to see an interesting piece of code that comes from these OO people."
"I think that object orientedness is almost as much of a hoax as artificial intelligence."
All the quotes above are from an interview with Alexander Stepanov, the inventor of the STL and elder statesman of generic programming.
To have a concrete idea about the generics flexibility, let’s compare the implementation of a class calculating a tax in OOP and generic programming.Let’s discover a major difference between the two methodologies, which could explain Alexander Stepanov’s opinion about the OOP approach. For that, let’s take this basic tax calculator as an example
CTaxCalculator collaborates only with classes of the ICalculator kind. Indeed, we have to inherit from ICalculator and override some virtual methods to implement our algorithm.
On the other hand, here’s an example of the generic TaxCalculator
The CGenericTaxCalculator class does not collaborate only with a specific kind of class, but with any type capable of calculating the tax; it’s not aware of the type’s kind.
The OOP approach is more an “is-oriented approach”: inheritance is overused, and in almost all OOP code, each class A collaborates with another class B if B is a kind of another class, abstract or not.
On the other hand, with the generic approach a class A collaborates with B if B has some specific methods and fields — no need to inherit from a specific class.
This makes generic programming more natural and flexible: it gives the developer the possibility to adopt a “has-oriented approach”. OOP is more rigid due to the high coupling generated by inheritance, which forces the developer to follow an “is-oriented approach”.
Think about it: the “has-oriented approach” is the more natural one. Indeed, in the real world I collaborate with a person who has specific skills, no matter whether they are from a specific family.
The fact that generic programming is more flexible than OOP makes it the preferred choice for modern C++ design, as pointed out by Andrei Alexandrescu:
Modern C++ Design defines and systematically uses generic components - highly flexible design artifacts that are mixable and matchable to obtain rich behaviors with a small, orthogonal body of code.Three points in his statement are interesting:
- Modern C++ Design defines and systematically uses generic components.
- Highly flexible design.
- Obtain rich behaviors with a small, orthogonal body of code.
To sum up, generic programming is more natural and flexible than the OOP approach, and it gives more possibilities to write efficient code.