[boost] Re: Formal Review: Circular Buffer

From: David Abrahams (dave_at_[hidden])
Date: 2004-03-07 08:42:43

Alberto Barbati <abarbati_at_[hidden]> writes:

> Suppose that T *is* assignable, is destroy+copy construction better
> than assignment? Probably no, for several reasons, including:
>
> 1) assigment is probably more efficient. In particular it might avoid
>    destruction/reconstruction of sub-objects non related with the
>    class invariant (for example: buffers, mutexes, etc.).
>
> 2) with the dtor/ctor idiom, if the ctor throws an exception, the old
>    element is lost and you can't do anything about it, so the
>    container cannot provide more than the basic guarantee for any
>    method that might overwrite elements. However, the user might
>    implement assigment with the strong guarantee, the container might
>    leverage on that and provide the strong guarantee too at least for
>    methods that might overwrite a single element such as
>    push_back/push_front. (Of course, the user might implement
>    assignment so badly that it doesn't provide even the basic
>    guarantee and the container could not recover from that, but a
>    library such not try to outsmart the user... too much ;).
>
> Just my opinion,

Well said.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com