Keynote: Object-oriented programming and generic programming and what else?

Bjarne Stroustrup

Programming styles

OOP and GP and Concurrency

We must evaluate programming styles/paradigms against a set of ideals.

Aims for
· For developers
· For programmers
· Etc

Programming languages are a means for expressing solutions; they still matter!

Classic OOP problems
· Double dispatch: intersection amon two objects
· Eternal polymorphism: adding operations to something
· Etc

Classic GP
Advantages
· Regularity and generality of code
· Shared implementation
· Composability
· Performance

Ex:
list lst;
int s1 = accumulate(lst.begin(), lst.end(),0)
int p1 = accumulate(lst.begin(), lst.end(),1,multiply());
vector v;
Matrix s2 accumulate(v.begin(), v.end(),0);

C++ GP: run-time efficiency with a high-level of abstraction
Classic template ex: prime # calculation by the compiler

Classic GP problems
· Irregularities of argument types
· No support for defining new types

OOP vs. GP

OOP: Ad-hoc polymorphism
GP: Parametric polymorphism

OOP: focus on design and use of hierarchies
GP: focus on design and use of algorithms

OOP: Dynamic (run-time) resolution of calls
GP: Static (compile-time) resolution of calls

OOP: Easy to add new type
GP: Hard to add new type

OOP: Hard to add new operation
GP: Easy to add new algorithm

There are solutions in the space that involves the combinations of these two styles.

Can we combine/extend these two styles to minimize problems? Bjarne’s guess: the convergence will hinge on concurrency

C++0x Concepts and Concept maps push GP support to more mainstream.

Concept maps help fix separately developed libraries together provided they are somewhat similar in semantics.

GP: runtime concepts (currently research)

References
· Design Patterns, 1994
· Concepts: Linguistics Support for Generic Programming in C++, OOPSLA ‘04
· Run-time concepts for the C++ standard library, SAC ‘08
· The C++ Programming Language, 2000