Just because you don't see it, doesn't mean it's not happening.
- Have you ever heard about how Walmart handles Black Fridays?
- Do you even know what's behind Apple's payment system?
- You ever used Pandoc, Couchbase, Grammarly, CircleCI, Clubhouse.io, Pandora, Soundcloud, Spotify?
- Have you ever asked a question - what is an app like WhatsApp that was sold for $19 Billion runs on?
- or How Facebook fights spam, Cisco does malware detection or AT&T deals with abuse complains?
- How Clojure is used at NASA or how Microsoft uses Haskell?
Frankly, I don't even know what's there to debate about. Functional programming is already here and it's been used in the industry for quite awhile already and its usage growing in a quite steady pace. Almost every single programming language today has certain amount of FP idioms, either built-in or via libraries. So yeah, while you're sitting there, contemplating about if FP useful or not, people been building hundreds of awesome products.
I said: it's not _that_ useful. I did not say it's completely useless.
Every large (or even small) company has people writing stuff in Perl, Bash, Haskell, Ruby, Rust, VBA, Scala, Lua or what not. I've been that guy, too.
More often than not it is a distraction more than anything, and it ultimately ends up being rewritten in C++, Java or Python. I think there are some niches where it helps; OCaml has had some success with static analysis and proof assistants, or even with code generation projects like FFTW.
Honestly, do you really think a company with only 35 engineers could build, scale and sell a product like WhatsUp for even a fraction of that amount but using C++, Java or Python? I seriously doubt that.
Look, I've seen both sides and I know this for sure (this isn't a mere opinion, this is a certain fact) - FP allows to build and maintain products using smaller teams.
You don't have to trust my word, do your research, google "companies using Clojure" (or Haskell, OCaml, Erlang, etc). You will see that either those companies are not too big, or the FP teams in large companies not very large.
Skeptics often cite this fact, claiming it to be the proof that FP codebases don't scale to large teams. The truth is - you don't need a big team to build a successful product with FP language. And the number of startups using FP langs is steadily growing.
- Have you ever heard about how Walmart handles Black Fridays?
- Do you even know what's behind Apple's payment system?
- You ever used Pandoc, Couchbase, Grammarly, CircleCI, Clubhouse.io, Pandora, Soundcloud, Spotify?
- Have you ever asked a question - what is an app like WhatsApp that was sold for $19 Billion runs on?
- or How Facebook fights spam, Cisco does malware detection or AT&T deals with abuse complains?
- How Clojure is used at NASA or how Microsoft uses Haskell?
Frankly, I don't even know what's there to debate about. Functional programming is already here and it's been used in the industry for quite awhile already and its usage growing in a quite steady pace. Almost every single programming language today has certain amount of FP idioms, either built-in or via libraries. So yeah, while you're sitting there, contemplating about if FP useful or not, people been building hundreds of awesome products.