As I said, they're not necessary and I don't think I've written useful code that explicitely used monads, for example - well, aside from for-comprehensions, but you could argue that it's not explicit.
But they are fun in that, once you start understanding what the fuss is all about, they open your brain to new ways of thinking, which is always good - instead of learning how to be really really good with a hammer, I like to know about screwdrivers as well, for the odd case where that nail is kind of screwy.
I do understand your point about an infinite amount of things to learn in a finite amount of time. What I personally do is focus my study of tedium (build tools, say) and domain-specific concepts for work-hours. These things are required for me to be good at my job, and it seems fair that I improve on them while doing that job.
The other, more theoretical (type theory, functional abstractions, fun data structures...) or less directly applicable (odd languages, new concepts such as reactive programming or actors...) subjects I study on my own time, when I have it, when and if I feel like it.
It means that, for example, it took me a solid year before I felt I had some degree of fluency in Scala, which was frustrating. On the plus side, I now have some degree of fluency in Scala.
But they are fun in that, once you start understanding what the fuss is all about, they open your brain to new ways of thinking, which is always good - instead of learning how to be really really good with a hammer, I like to know about screwdrivers as well, for the odd case where that nail is kind of screwy.
I do understand your point about an infinite amount of things to learn in a finite amount of time. What I personally do is focus my study of tedium (build tools, say) and domain-specific concepts for work-hours. These things are required for me to be good at my job, and it seems fair that I improve on them while doing that job.
The other, more theoretical (type theory, functional abstractions, fun data structures...) or less directly applicable (odd languages, new concepts such as reactive programming or actors...) subjects I study on my own time, when I have it, when and if I feel like it.
It means that, for example, it took me a solid year before I felt I had some degree of fluency in Scala, which was frustrating. On the plus side, I now have some degree of fluency in Scala.