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.

I mean, you can go all the way to the deep end, but like any tool, there are good reasons to be pragmatic, and avoid just using a tool for its own sake. Sure, you can get lost in fantasy land[0] algebras if you really want to, but generally I see it as a pyramid of usage (i.e. a small number of people that care about the mathematics, a slightly larger group of library authors that use fantasy land and friends to inform API design decisions, and a larger portion of library consumers that benefit from the academic roots of those design decisions.)

[0] https://github.com/fantasyland/fantasy-land