[cnasc]

I've used J (a language in the APL lineage) as an interactive calculator before. It makes some things pretty easy, especially if you need to operate on series of numbers.

What's the sum of the numbers from 15 to 20 inclusive?

  i.6 N.B. Returns an array 0 1 2 3 4 5

  15 + i.6 N.B. Returns an array 15 16 17 18 19 20

  +/ 15 + i.6 N.B. returns the number 105

edit: Or course, if we're talking about languages helpful for calculation, we simply must include a reference to https://frinklang.org/