Simply send a string containing a mathematical expression and get the answer in return. If the expression is malformed or errors out, no response will be sent back.
Example usage:
if event.type == "program" then
digiline_send("fpu", "18 + 3 / (-10 - 8.5)")
elseif event.type == "digiline" then
digiline_send("<some output device channel>", tostring(event.msg))
end