elegant way to count items

Question

I have a list shaped like this:

  \'((\"Alpha\" .  1538)
    (\"Beta\"  .  8036)
    (\"Gamma\" .  8990)
    (\"Beta\"  .  10052)
    (\"Alpha\" .  12837)
           


        

Answer 1

Using high-order functions sort and reduce.

First sorting (using string<) then reducing (counting consecutive string= values in cons cells):

(reduce (lambda (r e)
          (if (and r (string= (caar r) e))
              (cons
               (cons (caar r) (1+ (cdar r)))
               (cdr r))
            (cons (cons e  1) r)))
        (sort (mapcar 'car alist) 'string<)
        :initial-value nil)