[Tarantino]

Hello all

I want to do a simple math in TUI as the following:

(define a pick-a-real "report surface-integrals volume-flow-rate bc1 ,,")
(define b pick-a-real "report surface-integrals volume-flow-rate bc2 ,,")

(- a b)

and I got this error:

Error: - (subtract): invalid argument [1]: wrong type [not a number]
Error Object: #[compound-procedure]


I tried also:

(rpsetvar 'x (pick-a-real "report surface-integrals volume-flow-rate bc1 ,,"))
(rpsetvar 'y (pick-a-real "report surface-integrals volume-flow-rate bc2 ,,"))

(- x y)

and I got this error:

Error: eval: unbound variable
Error Object: x

Anyone know what is the problem and how can I fix it?
Thanks.