If you change
to some other number, and want to know the sum of three
s again, you can avoid re-typing the form which computes it. To see how this is done, follow the instructions below.
(setq val 1).
is now set to 1.
Alt+Por choose History > Previous or click
PROMPT > (setq val 1)
The form you previously typed appears at the prompt. At this point, you could edit this form and press
to evaluate the edited form. For the moment, just carry on with the next instruction.
Alt+Pagain, and then press
PROMPT > (+ val val val)
a second time displayed the second to last form that you evaluated. This time, pressing
immediately afterwards simply re-evaluates the form. Note that you could have edited the recalled form before evaluating it. You can use
repeatedly, recalling any form that you have evaluated in the current session.
This time the form evaluates to the number
, because the value of
was changed in the interim.