Well "bc" is still included with macOS. "bc -l" to start it in a useful mode. It's slightly quirky, but very powerful.

For example, "4*a(1)" to calculate pi.

I don’t really understand how you could read the parent comment and then suggest bc as a reasonable equivalent. For one thing I find interacting with bc to not be so interactive as gnu calc—you have to type one line at a time and it is hard to see intermediate results or make modifications. For a second thing, I don’t think bc includes:

- differentiation

- symbolic/numeric integration

- equation solving/manipulation

- unit conversion

- graphing

- vectors and matrices

- functional array operations like map/reduce

- statistical operations

- a detailed manual

Personally my main use of bc is:

  ... | paste -s -d+ | bc

I often just:

    $ python
    from math import *

When you have a hammer...

And dc (the original desk calculator) if you want RPN. I pretty much always have a terminal window with dc running for quick math. It's good for doing base conversions too.

how do you use this function? I am aware that Emacs keybinding (C-n, C-p, C-M-f) can be used in macOS' text inputs, but I somehow cannot trigger C-x to work

This keybinding is meant to be used inside Emacs.

I see...

I get your previous comment wrong then