NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/std/c++/634

Text File | 1996-08-06 | 3.3 KB | 76 lines

Path: chronicle.mti.sgi.com!austern
From: [e-mail] (James Kanze US/ESC 60/3/141 #40763)
Newsgroups: comp.std.c++
Subject: Re: STL pop_back()
Date: 05 Mar 1996 09:46:27 PST
Organization: GABI Software, Sarl.
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X-Original-Date: 05 Mar 1996 11:57:41 GMT
In-Reply-To: Hayden Schultz's message of 05 Mar 96 07:58:26 GMT
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In article <[e-mail]> Hayden Schultz <[e-mail]>
writes:

|> According to _STL Tutorial and Reference Guide_ by Musser and Saini
|> (a very good book, btw), the following functions are defined:

|> template <class T> void vector<t>::pop_back();
|> template <class T> void deque<t>::pop_back();
|> template <class T> void deque<t>::pop_front();
|> template <class T> void list<t>::pop_back();
|> template <class T> void list<t>::pop_front();

|> Other classes may have pop functions, I dunno.

|> Why don't the pop functions return a copy of the object before they
|> blow it away? Another possibility, I suppose, would be an auto_ptr<T>
|> so that the object is deleted if it's not used. An auto_ptr<T> is
|> about as efficient as deleting it in the pop function, it just changes
|> the time it's deleted (which isn't guaranteed anywhere I've read
|> anyway).

I suspect that no copy is returned because of performance reasons: to
return one would require making the copy in every case (whether it was
used or not), then destructing it.

I don't understand the remark concerning auto_ptr.  In order to return
an auto_ptr to the object, it would be necessary to allocate a new
copy of the object on the stack, then delete it.

I suppose some sort of intelligent reference could be returned, which
would destruct the object whenever it was destructed.  This might
still cause problems freeing the memory; I suppose that they would be
solvable.

But is it worth it?

|> Why call the methods push and pop if it doesn't act like a stack?

That is the real question.  A list is not a stack.  A deque is not a
stack.  A vector is not a stack.  The functions pop_front and pop_back
have nothing to do with the operation pop on a stack.  This is why it
is not worth the bother of having them return a value.  This is also
why it probably would have been better if they'd have had another
name.
--
James Kanze         Tel.: [phone]        email: [e-mail]
GABI Software, Sarl., 8 rue des Francs-Bourgeois, F-67000 Strasbourg, France
Conseils, Θtudes et rΘalisations en logiciel orientΘ objet --
                -- A la recherche d'une activitΘ dans une region francophone
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