Why Functional Programming Matters
--- in an Object-Oriented World

Matthias Felleisen

At first glance, the object-oriented approach and the functional ideal of programming clash. One refers to objects that change state and respond to messages; the other appeals to the purely mathematical notions of functions and sets. Similarly, object-oriented programmers use patterns to design programs and parts of programs, while functional programmers heavily rely on pattern-matching and recursion.

In this talk I compare the two programming paradigms in four different respects:

• the perception of what matters
• the underlying computational model
• methods of program design
• tools for abstraction, i.e., creating single points of control

By focusing on the essence of these four aspects, we discover that functional programming and object-oriented are closely related, and why the two communities can and should readily exchange results and ideas.