(speaking for myself) I focus on why a language looks interesting and worthwhile to learn - i.e. what new ideas are in it that are worth stealing. Over and ov

(speaking for myself) I focus on why a language looks interesting and worthwhile to learn - i.e. what new ideas are in it that are worth stealing. Over and over, I've found that grasping the new ideas in one language almost always permits you to use it in another more "mundane" language. I've for example used C++ functionally, brought Objective-C and Erlang ideas into C++ and so on when I was dominantly programming in C++. During that period, I also made a scheme-dialect interpreter in C because for some of the things we wanted to do C/C++ were too hard boiled. More recently, I've brought CSP into Javascript through sweet.js so I can write go-routines in JS, and along the way also brought Mozart/Oz's "data flow variables" a.k.a. promises as native to JS (again through sweet.js). I've also run a short fun "course" at my company called "no spoon" where the participants build a stack-based language in JS and implement many defining features of many other programming languages .. including all the above. So what I'm trying to say is that you don't need to lament that you can't use a language that you learnt in your day job. New ideas in languages are always worth learning no matter what language you work with on a day-to-day basis.