Mapping a function over `frame-list` to get a list of the `top` frame-parameter values

Question

I'd like to make a list of parameters of each frame such as the top coordinate, left coordinate, and name to achieve what I asked in my previous question. I'm trying to follow the advice I got there and wrote a snippet to print the top coordinates of each frame, but it doesn't work. Could anyone tell me which part is wrong?

(message "%s" (mapcar (cdr (assq 'top (frame-parameters)))) (frame-list))

It returns

Invalid function:(mapcar (cdr (assq 'top (frame-parameters))))

Answer 1

It turned out that I needed lambda. This worked.

(message "%s" (mapcar  (lambda (x) (cdr (assq 'top (frame-parameters x) )))(frame-list) ))