in reply to David Goldfield

If you are really looking for something functional and have some technical knowhow, it's CLI though, check out calc, isthe.com/chongo/tech/comp/cal…. It's a C-style arbitrary precision calculator with absolutely gobs of functions, it's got readline for history, variables, the ability to define functions including in an rc-style file I think etc. Doesn't build natively on Windows, but you can build it in Cygwin.
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