Re: Logical Value Of A Pointer
On 2009-01-30 16:36:32 -0500, Bertrand <bertrand_duret@yahoo.co.uk> said:
btw, if example of the STL serves, several classes provide an implicit
conversion to bool to express the meaning of /valid/. streams are an
example.
Well, an implicit conversion to void*, which in turn implicitly
converts to bool. But, yes, it's a standard idiom.
On the other hand, implicit conversion to void* worries folks with too
much time on their hands, since someone might delete that object. So
they insist that these things return something that can't be deleted.
Of course, now that the language allows "explicit" on a conversion,
we'll see all sorts of conversions being marked explicit. But explicit
conversions to bool work are applied in boolean contexts, so
if(my_obj)
will use the explicit conversion.
Ok, admittedly, the most relevant one to the present discussion
precisely lacks it (std::auto_ptr). However, I don't think your
argument holds for it either:
if( p.get() == 0 )
does not /mean/ more than:
if( p.get() )
boost::shared_ptr also defines an implicit conversion to bool. So if
Boost does it, it does not look like a bad practice to me.
To add to the length of this thread, i will mention that I have a
personal preference for:
p ? p->something : something_else;
over:
p == 0 ? p->something : something_else;
It's pretty clear what's going on in former case, so no need to be over
redundant.
The term "over redundant" is brought to you by the Department of
Redundancy Department.
It's a bit like those who write:
if( condition == true )
or:
return condition ? true : false;
or even:
return condition == true ? true : false;
But why stop there?
if ((condition == true) == true)
ad infinitum.
--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)