I don’t really mind having a non-POSIX shell since it doesn’t prevent bash scripts from working, but I get that if you want portability bash is still best since it’ll work mostly anywhere.

rofi-calc is awesome. It’s so convenient to just press a keyboard shortcut you have defined and instantly being able to type or paste your equation, no having to wait for a complicated GUI to load, no clicking required. You can just pop it in whenever you need. Also it does unit conversions, instead of a math equation you can just type 10 inches to cm or 10 eur to usd or 100 celsius to fahrenheit or 100 to binary which is a huge time saver.

https://github.com/svenstaro/rofi-calc

Besides, it’s rofi and rofi rules 😎