[boost] Re: [string algo review] overloading on const

From: David Abrahams (dave_at_[hidden])
Date: 2003-10-23 11:51:41

Beman Dawes <bdawes_at_[hidden]> writes:

> At 10:47 AM 10/23/2003, Pavol Droba wrote:
>  >On Thu, Oct 23, 2003 at 11:28:38PM +1000, Thorsten Ottosen wrote:
>  >> I would say we have to provide
>  >>
>  >> template<typename InputContainerT, typename SearchContainerT>
>  >>     iterator_range< typename string_algo::container_const_iterator<
>  >> InputContainerT >::type >
>  >>     find_first(const InputContainerT &, const SearchContainerT &);
>  >>...
>  >
>  >Yes you have overlooked one important point. Your second proposed variant
>  >does not make sense and what worse, it is even very dangerous.
>  >
>  >find_xxx algorithms return a reference into the input container by the
>  >means
>  >of iterators. Using a temporary as an input, you would get an invalid
>  >reference as a result.
>  >
>  >Returning a reference from a temporary is quite a big error in my
>   opinion.
>
> What is the fix? There really needs to be some convenient way to do a
> find_first on a const container. Provide a version that takes begin
> and end iterators? Or is that already done by one of the algorithms in
> detail that you are going to move into boost::algorithm::string?

I'm not sure a fix is needed.  The first variant will already match
const containers, as long as they're not temporaries.

      
      template <class T>
      int f(T& x);

      int const x;
      int y = f(x); // T deduced as const int.

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