GNU bug report logs - #33731
26.1; cl-make-random-state copying not working

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Xu Chunyang <mail <at> xuchunyang.me>
Subject: bug#33731: closed (Fwd: 26.1; cl-make-random-state copying not
 working)
Date: Wed, 19 Dec 2018 22:29:02 +0000

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Your bug report

#33731: 26.1; cl-make-random-state copying not working

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 33731 <at> debbugs.gnu.org.

-- 
33731: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=33731
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: 33731-done <at> debbugs.gnu.org
Subject: Fwd: 26.1; cl-make-random-state copying not working
Date: Wed, 19 Dec 2018 14:27:59 -0800

[Message part 3 (text/plain, inline)]

Thanks for reporting this bug; it is a regression introduced when we 
separated records from vectors. I installed the attached patch into the 
emacs-26 branch.

[0001-cl-make-random-state-was-not-copying-its-arg.patch (text/x-patch, attachment)]

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From: Xu Chunyang <mail <at> xuchunyang.me>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.1; cl-make-random-state copying not working
Date: Fri, 14 Dec 2018 05:12:35 +0800

Hi,

I am reading (info "(cl) Random Numbers") on cl-make-random-state. I
expect the following returns two equal numbers, because s should be a
copy of cl--random-state thus two cl-random should use two equal
state.

(let ((s (cl-make-random-state)))
  (list (cl-random 10000)
        (cl-random 10000 s)))
;; => (6955 916)

If I didn't misunderstand this, I think it is because
cl-make-random-state uses copy-tree, however it doesn't work for
cl-structure at least in Emacs 26.1, it doesn't copy at all.

(eq (cl-make-random-state 123)
    (cl-make-random-state 123))
;; => nil

(let* ((s1 (cl-make-random-state 123))
       (s2 (cl-make-random-state s1)))
  (eq s1 s2))
;; => t

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