Re: [Boost-users] Boost range changes [1.37.0]

Subject: Re: [Boost-users] Boost range changes [1.37.0]
From: Tomas Puverle (Tomas.Puverle_at_[hidden])
Date: 2008-11-20 12:18:27

> template<class T>
> bool is_singular_or_empty(const T& t) { return(t.empty()); }

> template<class T>
> bool is_singular_or_empty(const iterator_range<T>& t) { 
> return(t.is_singular() || t._empty()); }

Hey Steven,

That was my initial approach, too.  

>From a library designer point of view, the reason why I was reluctant
about the above
is that it breaks the range contract (begin, end, empty,...) and forces
my users to
be aware of the idiosyncrasies of a particular range implementation.

>From an implementation point of view, unfortunately, you seem to have
got caught out 
by the same problem as me - is_singular() is only useful in debug
builds.  
It always returns false in release builds and hence the above won't
work.  Worse, it will
break silently, as t.empty() will end up comparing invalid iterators in
release.  I am 
sure you can see how this would be very hard to find and debug.  This
also illustrates my
other big issue with having functions which work differently in
different builds.

Kind regards,

Tom