Question

if I use this I get an error because c is never set.

(if (symbol-value c)
    c
  nil)

my problem is that I have a list with containing symbols and some of them are set to some value, I want to construct a list with their values and nils

(setq a "x")
(setq b "y")
(setq l '(a b c))

so from l I want construct a list with ("x" "y" nil).
I think this should be some thing so simple

Answer 1

(setq a "x")
(setq b "y")
(setq l (mapcar (lambda (x)
                  (and (boundp x) (symbol-value x)))
                '(a b c)))