Why is this function name causing “Invalid function” when in a list for `dolist`?

Question

How can I use dolist to repeat an operation for each item in a list?

I have a sequence of statements:

(put 'downcase-region 'disabled nil)
(put 'upcase-region 'disabled nil)
(put 'narrow-to-defun 'disabled nil)
(put 'narrow-to-region 'disabled nil)
(put 'narrow-to-page 'disabled nil)
(put 'set-goal-column 'disabled nil)

that I want to re-factor by putting each name into a list, then repeating the operation for each name.

So I think the dolist function can achieve this.

This fails:

(dolist (command
  (
   'downcase-region
   'upcase-region
   'narrow-to-defun
   'narrow-to-region
   'narrow-to-page
   'set-goal-column
   )
  (put command 'disabled nil)))

with an error

Invalid function: 'downcase-region

Why is that an “invalid function” in one instance but not the other?

How should that dolist be written to achieve the same effect as the first example?

Answer 1

an error

Invalid function: 'downcase-region

Why is that an “invalid function” in one instance but not the other?

The error is complaining that it's been asked to invoke a function, named 'downcase-region.

This is because the list ('downcase-region 'upcase-region 'narrow-to-defun …) is evaluated immediately; which attempts to invoke a function named 'downcase-region. Which doesn't exist.

Instead of evaluating the list immediately, the list needs to survive as-is as a value for the dolist function. You do this by quoting the list.

(dolist (command
  '(downcase-region
    upcase-region
    narrow-to-defun
    narrow-to-region
    narrow-to-page
    set-goal-column
    ))
  (put command 'disabled nil))