[boost] Re: non-member reset()

From: David Abrahams (dave_at_[hidden])
Date: 2005-01-28 11:38:40

Daniel Frey <d.frey_at_[hidden]> writes:

> David Abrahams wrote:
>> Daniel Frey <d.frey_at_[hidden]> writes:
>> 
>>>David Abrahams wrote:
>>>
>>>>Rob Stewart <stewart_at_[hidden]> writes:
>>>>
>>>>
>>>>> swap() is typically as fast as or faster than copy assignment, 
>>>>
>>>>Not for many types that one might like to reset, such as pointers,
>>>>shared_ptr<T>, and integral types.
>>>
>>> What about exception safety guarantees of assignment vs. swap? 
>> What about 'em?  Speaking generally, both are basic guarantee
>> operations.
>
> I thought that swap is often (not always) a function which  doesn't 
> throw, e.g. containers' x.swap( y ). 

Often == sometimes == never guaranteed to be.  Same for operator=.

> If it is, it would make reset a function with the strong instead of
> the basic exception guarantee.
>
> But then, this might not be general enough to be worth the trouble... 
> OK, forget about it :)

Premature strengthening of exception guarantees is a common source of
inefficiency.

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