Why Isn't Functional Programming the Norm? [video]

The top comment on YouTube raises a valid point:

> I've programmed both functional and non-functional (not necessarily OO) programming languages for ~2 decades now. This misses the point. Even if functional programming helps you reason about ADTs and data flow, monads, etc, it has the opposite effect for helping you reason about what the machine is doing. You have no control over execution, memory layout, garbage collection, you name it. FP will always occupy a niche because of where it sits in the abstraction hierarchy. I'm a real time graphics programmer and if I can't mentally map (in rough terms, specific if necessary) what assembly my code is going to generate, the language is a non-starter. This is true for any company at scale. FP can be used at the fringe or the edge, but the core part demands efficiency.

I too have been programming professionally for nearly two decades. Much longer if you consider the time I spent making door games, MUDs, and terrible games in the 90s.

I think functional programming gives you powerful tools to reason about the construction of programs. Even down to the machine level it's amazing how amortized functional data structures change the way you think about algorithmic complexity. I think laziness was the game changer here. And if you go all in with functional programming it's surprising how much baseline performance you can get with such little effort and how easy it is to scale to multiple cores and multiple hosts.

There are some things like vectorization that most functional languages I know of are hard pressed to take advantage of so we still reach out to C for those things.

However I think we're starting to learn enough about functional programming languages and how to make efficient compilers for them these days. Some interesting research that may be landing soon that has me excited would enable a completely pure program to do register and memory mutations under the hood, so to speak, in order to boost baseline performance. I don't think we're far off from seeing a dependently typed, pure, lazy functional language that can have bounded performance guarantees... and possibly be able to compile programs that don't even need run time support from a GC.

I grew up on an Amiga, and later IBM PCs, and that instinct to think about programs in terms of a program counter, registers, and memory is baked into me. It was hard to learn a completely different paradigm 18 or so years into my professional career. And to me, I think, that's the great accident that prevented FP from being the norm: several generations were simply not exposed to it early on on our personal computers. We had no idea it was out there until some of us went to university or the Internet came along. And even then... to really understand the breakthroughs FP has made requires quite a bit of learning and learning is hard. People don't like learning. I didn't. It's painful. But it's useful and worth it and I'm convinced that FP will come to be the norm if some project can manage to overcome the network effects and incumbents.