Forgive me if this sounds ignorant, but who is using pure-functional approaches in industry?
Again, please correct me if I'm wrong since I've been industry for barely 2 years: back in school functional programming looked cool, but when I entered industry(and even in my exploration through personal/OSS projects), I have found it to be nothing more for the most part than a cool toy to play with. I can somewhat see the benefit when it comes to parallelizing Big Data, but that seems to be a very special case.
Again if I'm just being ignorant, please educate me :)
Lots of people take useful parts of the functional paradigm without bringing in the whole shebang. Javascript being at the top of the list of languages in that page is a good hint at how people use it: things like Array.map are often used instead of procedural counterparts because people consider the pipeline-like data flow to be easier to understand than ad-hoc for loops, to give one simple example.
Promises and the async/await syntax sugar on top of them are another JS construct that borrow quite a bit from functional literature.
I see what you mean...Even I myself have written code along the lines of "array.map.filter.this.filter". And indeed it can be more readable certain times. But I guess what I was referring to is that sometimes it seems that people are "preaching" functional programming as gospel. But I could be misinterpreting things.