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.

Classic games programmer logic. I've heard it a billion times. "X feature abstracts the hardware and therefore I could never use it for programming in my tiny niche and therefore it could never become popular."

And how many of the top 10 languages are running in a virtual machine? Which could be literally doing anything under the hood with your allocations, caching, etc?!

There is nothing wrong with saying, I don't see this working out in my domain due to these concerns it's just silly to say, I never see it taking off because it can't work in my domain.

I think this video nails it pretty dead on. My team works almost exclusively in C# these days for reasons mostly beyond our control. The team generally likes the language quite a bit (it's one of my personal favorites). But when I find myself asking for new features they come in two buckets. I'd like feature that help certain members of my team write less side effect heavy code and I'd like immutability by default with opt-in mutability. Basically I'd like more functional like features. But hey, that's what I see from my niche.

> And how many of the top 10 languages are running in a virtual machine? Which could be literally doing anything under the hood with your allocations, caching, etc?!

VMs provide an environment, just like any other. Javascript articles are chock full of information on how to not abuse the GC by using closures in the wrong place. C#'s memory allocation is very well defined, Java has a million tuning parameters for their GC, Go is famous for providing goroutines with very well defined characteristics.

Heck people who know C# can look at C# code and tell you almost exactly what the VM is going to do with it. And now days C# allows direct control over memory.

People writing high performance code on Node know how the runtime behaves, they know what types of loads it is best for, none of that is a mystery.

Sure some details like "when does this code get JITed vs interpreted" are left up to the implementation, but it isn't like these things are secret. I think every major VM out there now days is open source, and changes to caching behavior is blogged about and the performance implications described in detail.

The fact is, all programming paradigms are merely ways to limit our code to a subset of what the machine can do, thereby making reasoning about the code easier.

They are purely mental tools, but they almost all have a performance cost for using them. They are turing complete tools of course, any solution is theoretically solvable with any of the major paradigms, but not every paradigm is appropriate for every problem.

So, you know, pick the paradigm that makes it easiest to reason about the problem space, given acceptable performance trade offs.