Re: def app = apply, problem

g> i dont know the operator

so you'll be calling passing a variable: (app op (1 2 3))
won't it be easier to use (funcall op 1 2 3)?

Common Lisp already has large set of functions, operators and macros that
make sense.
most of stuff you can invent will make no sense OTOH

g> and its merely educational anyway.

rather than inventing random "stuff", it would be much more educational to
try to emulate various special operators/macros via a limited set of other
ones:

emulate if via cond (and vice versa)

let* via let

labels via flet (this is quite challenging)
....


.