math/calc 2.17.0.2 OpenBSD

Calc is an interactive calculator which provides for easy large numeric calculations, but which also can be easily programmed for difficult or long calculations using a C-like language featuring variable declarations, expressions, tests, labels, loops, file operations, and function calls, and with a rich set of builtin mathematical and programmatic functions.

It can accept a command line argument, in which case it executes that single command and exits. Otherwise, it enters interactive mode. In this mode, it accepts commands one at a time, processes them, and displays the answers. In the simplest case, commands are simply expressions which are evaluated.