From: jun <netjune@163.com>
To: "Elias Mårtenson" <lokedhs@gmail.com>
Cc: emacs-devel <emacs-devel@gnu.org>
Subject: Re:Re: Can we add two args to copy-sequence?
Date: Fri, 15 Dec 2017 22:52:09 +0800 (CST) [thread overview]
Message-ID: <41cc6ca4.f2de.1605aa9400f.Coremail.netjune@163.com> (raw)
In-Reply-To: <CADtN0WKT=4-RzJu8asV6HKRWmJioAerAwzi9Fpr4x7bgPNJZfw@mail.gmail.com>
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Yes, I just know subseq. And there are also seq-subseq, seq-take, seq-drop, butlast, Two many and hard to remmber.
Almost all of them are implemented in lisp except copy-sequence which is in C. Some of them are implemented
by copying the whole sequence and then modify the copy. If we add the two args to copy-sequence,
then these functions can be based on it with only one or two lines in lisp, and reduce some data copy.
Does the two args make copy-sequence too much complex internally?
在 2017-12-15 16:24:50,"Elias Mårtenson" <lokedhs@gmail.com> 写道:
On 15 December 2017 at 15:54, John Wiegley <johnw@gnu.org> wrote:
>>>>> "j" == jun <netjune@163.com> writes:
j> like this: (copy-sequence seq &optional from to). 'from' and 'to' mean the
j> same as in the function 'substring'.
I'd rather not overload copy-sequence that way, and rather have a new function
named (sublist LIST &optional FROM TO), even if copy-sequence xs == sublist xs.
There is already the function ‘subseq’ that does exactly this, or did I misunderstand
the question?
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next prev parent reply other threads:[~2017-12-15 14:52 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-15 3:32 Can we add two args to copy-sequence? jun
2017-12-15 7:54 ` John Wiegley
2017-12-15 8:24 ` Elias Mårtenson
2017-12-15 14:52 ` jun [this message]
2017-12-16 6:18 ` John Wiegley
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