count char in string [The Emacs Challenge Competition - round 2, with fallout]

[Emanuel Berg via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>]

round 1:

  https://lists.gnu.org/archive/html/help-gnu-emacs/2020-10/msg00524.html

fallout:
  1. Daniel Martín (1 point)
  2. Emanuel Berg  (-2)

Yes, your read it right, incorrect answers are "awarded" -2 points.
This is like the Russian or Cuban Olympic/Amateur boxing program -
only gold counts!

But: doesn't that mean that people will be afraid to post? Again, in
the Russian and Cuban Olympic/Amateur boxing programs, we are not
concerned with people who are afraid...

round 2:

Very simple: we are looking for a function that returns the number of
occurrences of a char in a string.

Emanuel Berg's solution:

(require 'cl-lib)
(defun count-char-in-string (the-char str)
  (let ((c  (if (characterp the-char) the-char (string-to-char the-char)))
        (cs (string-to-list str)) )
    (cl-count c cs) ))
;; (count-char-in-string ?a "Emacs skills kills") ; 1

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