Re: [boost] Re: Re: [filesystem] Operations predicates

From: Peter Dimov (pdimov_at_[hidden])
Date: 2005-05-05 04:39:16

Beman Dawes wrote:
> "Rob Stewart" <stewart_at_[hidden]> wrote in message
> news:200505041425.j44EPnrb027885_at_weezy.balstatdev.susq.com...
> 
>>   status_flag status(path const &, int * error = 0);
>> 
>> It is simpler from an implementation standpoint, but I don't
>> think it is simpler from the caller's perspective.  Since the
>> argument is defaulted, the compiler will offer no help to ensure
>> that you get and inspect the error number.
>> 
>> Returning a type with the flags and error number together means
>> that you always get the error number and can inspect it.  Whether
>> you use any schemes to ensure that the caller inspects a non-zero
>> error number -- such as asserting in the destructor if an
>> "inspected" flag isn't set -- is another matter.
> 
> That seems like a convincing argument.

Typical uses:

if( status( p ) & file_flag ) // ...
if( status( p, &e ) & file_flag ) // ...

vs

if( status( p ).flags & file_flag ) // ...

status_result r = status( p );
if( r.flags & file_flag ) // ...

I don't see much of a difference here.