220 7654 <CD8CC325-026A-4020-812A-AAF9927B9BBE@gmail.com> article
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From: Howard Hinnant <howard.hinnant@gmail.com>
Newsgroups: gmane.comp.lang.c++.isocpp.proposals
Subject: Re: Re: Could we remove the size() method in the std::list<T>?
Date: Sat, 9 Nov 2013 14:53:47 -0500
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On Nov 9, 2013, at 11:33 AM, euloanty@live.com wrote:

> 1.It makes most of the operations of std::list slower;
> 2.std::forward_list don't have this method. This makes people very confus=
ed.
> 3.the method splice() becomes much slower.
> 4.We know our library couldn't make people very confused. That was why we=
 didn't define the operator[] in the std::list<>;
> 5.The function of this method can be easily implied by programmers themse=
lves. We know this function had been defined clearly in cpp11, but in the c=
pp98, its time-complexity is not defined clearly. For this reason, in the p=
ast we almost didn't use it. So  I think this change won't make so many cod=
es invalid.

We can't remove the size() member of list because it would break far too mu=
ch code.

Here is an old write up of mine, but explores some of the rationale as to h=
ow we got where we are today.  It also includes a proposal for a new list::=
splice signature, that I still think is a good idea, but was firmly turned =
down by the LWG years ago.  The new list::splice signature would allow the =
client to pass in the size of the spliced range (if known) which makes this=
 splice function O(1).  And every time I've needed to splice "some from oth=
er", there is an opportunity for the client to count the range being splice=
d as the range is being created, with negligible extra cost.  I.e. creating=
 the range to be spliced is nearly always an O(N) operation for the client.

http://home.roadrunner.com/~hinnant/On_list_size.html

Howard

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