What's the difference between ' and #' in Lisp?

Question

It seems both

(mapcar \'car \'((foo bar) (foo1 bar1))) 

and

(mapcar #\'car \'((foo bar) (foo1 bar1)))

w

Answer 1

Try passing an anonymous function (lambda) to your mapcar and you'll see that #' is required since the quote by itself expects a symbol that is bound to a function, but the symbol doesn't exist in an un-named function:

CL-USER> (mapcar '(lambda (x) (format t "it is ~d" x)) (list 3 5 7))
; Evaluation aborted on #.

vs:

CL-USER> (mapcar #'(lambda (x) (format t "it is ~d" x)) (list 3 5 7))
it is 3it is 5it is 7
(NIL NIL NIL)