remove-duplicates performances

[Thierry Volpiatto <thierry.volpiatto@gmail.com>]

Hi all,
i just noticed that `remove-duplicates' is very slow.

Something like below seem much faster:

--8<---------------cut here---------------start------------->8---
(defun* remove-dups (seq &key (test 'eq))
  (let ((cont (make-hash-table :test test)))
    (loop for elm in seq
       unless (gethash elm cont)
       do (puthash elm elm cont)
       finally return (loop for i being the hash-values in cont collect i))))
--8<---------------cut here---------------end--------------->8---

Test:

(setq A (let ((seq (loop for i from 1 to 10000 collect i)))
          (append seq seq)))
(1 2 3 4 5 6 7 8 9 10 1 2 ...)

(remove-dups A)
(1 2 3 4 5 6 7 8 9 10 11 12 ...)
elp-results: remove-dups    1           0.013707      0.013707

(remove-duplicates A)
(1 2 3 4 5 6 7 8 9 10 11 12 ...)
elp-results: remove-duplicates  1           66.971619     66.971619

Would be nice to improve performances of `remove-duplicates'.

-- 
A+ Thierry
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