You’d expect the longest and most costly phase in the life cycle of a software product to be the initial development of the system, when all those great features are first imagined and then created. In fact, the hardest part comes later, during the maintenance phase. That’s when programmers pay th
Which industry?
Programming is more than just writing Yet Another CRUD-backed data-siphoning web app. It’s more than supercomputing/high performance computing. It’s more than spreadsheets and word processors. It’s more than games.
Any one of those fields I mentioned are effectively a completely separate industry from the others. And I haven’t even touched the 500kg gorilla of embedded systems that outnumber all of those put together by an order of magnitude or two.
Some software industries (the web stuff, say, or user-facing software like spreadsheets and word processors) will find pure functional or major steps along that path to be useful and an improvement over current techniques. Others (high performance computing, games) will find themselves stepping backward if they go the full-functional route. And that 500kg gorilla I mentioned simply can’t use functional programming. (Hell, I don’t think there’s a pure-functional runtime that fits into any of the kit I work on, not to mention the runtime plus an actual application. I’m willing to be corrected, though: if there’s a functional language out there that will let me write non-trivial applications that fit in 256KB code space and 48KB dynamic data space, I’m eager to hear about it!)
However much you think you know about software development, be aware that it’s far larger than you think. (This applies to me too. I haven’t even glanced at financial or health software’s direction, and only have very vague notions of what aerospace systems entail.) And as a result, different tool sets are required for different problem domains. Functional doesn’t fit them all.
I generally take your point, though I believe FP can be applied to most domains with some benefit - it is just that existing, prevalent FP languages may not always be well suited for the job. In HPC for instance, there are a few interesting options:
For both games and HPC, Futhark may be of interest: “Futhark is a small programming language designed to be compiled to efficient parallel code. It is a statically typed, data-parallel, and purely functional array language in the ML family, and comes with a heavily optimising ahead-of-time compiler that presently generates either GPU code via CUDA and OpenCL, or multi-threaded CPU code.”
Sadly I can’t find it right now, but there was research language designed with the idea of separating the implementation from the specification, in such a way that the implementation could still be verified to conform to the specification; the specification was much more than a typical function signature as I recall. Basically you would write the function specification in a functional style, and then be able to have multiple implementations (e.g. for different hardware) conforming to that specification. I want to say this was from Standford but may be wrong about that.
Futhark is of interest as a future direction, chiefly as a supplementary language for sub-pieces of a larger, performance-intensive program. Note that its creators, however, explicitly state:
This is not a negative point, incidentally! I personally use a lot of languages in my work because I find it’s better to use a tool honed to near-perfection for a particular use case than it is to employ another tool that does something not quite the same with lower quality. I wish more programmers learned more tools so they stopped doing the programming equivalent of hammering nails with a large wrench.