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Re: What to do for faster `remove-duplicates'?
From: |
Artur Malabarba |
Subject: |
Re: What to do for faster `remove-duplicates'? |
Date: |
Wed, 6 May 2015 20:24:42 +0100 |
2015-05-06 19:41 GMT+01:00 Oleh Krehel <address@hidden>:
> Artur Malabarba <address@hidden> writes:
>
>> But that nreverse could be optimized out if the first loop followed a
>> `while'+`setcdr' strategy like the second.
>
> Please check the optimized version:
>
> (defun delete-dups (list)
> "Destructively remove `equal' duplicates from LIST.
> Store the result in LIST and return it. LIST must be a proper list.
> Of several `equal' occurrences of an element in LIST, the first
> one is kept."
> (if (> (length list) 100)
> (let ((hash (make-hash-table :test #'equal)))
> (let ((tail list)
> elt retail)
> (while (setq retail (cdr tail))
> (setq elt (car retail))
> (if (gethash elt hash)
> (setcdr tail (cdr retail))
> (puthash elt t hash))
> (setq tail retail))))
> (let ((tail list))
> (while tail
> (setcdr tail (delete (car tail) (cdr tail)))
> (setq tail (cdr tail)))))
> list)
I may be wrong, but it looks like it's completely skipping the car of the list.
- What to do for faster `remove-duplicates'?, Oleh Krehel, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Stefan Monnier, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Oleh Krehel, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Stefan Monnier, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Oleh Krehel, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Thierry Volpiatto, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Oleh Krehel, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Artur Malabarba, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Artur Malabarba, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Oleh Krehel, 2015/05/06
- Re: What to do for faster `remove-duplicates'?,
Artur Malabarba <=
- Re: What to do for faster `remove-duplicates'?, Oleh Krehel, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Artur Malabarba, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Thierry Volpiatto, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Stefan Monnier, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Stefan Monnier, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Artur Malabarba, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Artur Malabarba, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Oleh Krehel, 2015/05/06
- Re: What to do for faster `remove-duplicates'?, Artur Malabarba, 2015/05/06