Re: Would seq-range and seq-mapcat be useful?

[Nicolas Richard <theonewiththeevillook@yahoo.fr>]

Oleh Krehel <ohwoeowho@gmail.com> writes:
> Is this already somewhere?

IDK, but I often wrote this kind of snippet for that purpose :

(defun yf/seq-group-by (fn lst)
  (let ((hash (make-hash-table :test 'equal)))
    (dolist (elm lst)
      (push elm (gethash (funcall fn elm) hash)))
    hash))

(yf/seq-group-by
 #'car
 '(("a" 1)
   ("b" 2)
   ("b" 5)
   ("c" 1)))
=> #s(hash-table size 65 test equal rehash-size 1.5 rehash-threshold 0.8 data
            ("a"
             (("a" 1))
             "b"
             (("b" 5)
              ("b" 2))
             "c"
             (("c" 1))))

-- 
Nicolas Richard