Question

I’m doing more interactive development with the REPL lately, and I have a section of code that pushes a symbol onto a global dynamic variable (a list data structure). Problem is, I find myself repeatedly reloading the file that pushes that symbol onto the global, so each time I reload, I get another duplicate symbol pushed onto the list.

I’d like for the push operation to be done only once for each lisp session, regardless of the number of recompiles/reloads, to mimic how things will behave in a more traditional/deployed environment, when I load the code only once for a lisp session.

Here’s the method I’m using now. I hope there’s a better way….

(defvar *do-only-once*
  (progn
    (push 'some-val *some-global-lst*)
    'evaled))

Answer 1

I would just use PUSHNEW instead.