If you want a lighter-weight package featuring a plaintext REPL, a large library of functions, function definition, arbitrary precision, and more (minus solver capability), give Speedcrunch a try:
You can make Speedcrunch look like a good old fashioned bc session, whereas Qalculate puts way too much stuff on the screen. It misses a simple REPL mode.
Qalc has poor documentation so I don't find learning its extra features to be worthwhile.
Qalc is also awkward to type.
Edit: https://www.friendlyskies.net/speedcrunch/
Kinda funny but also impressive in its way...
I have it on speed dial (pause / break key to open and close) and use it all the time.