Re: [boost] [range][foreach] Range fixes broke foreach

From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2007-10-24 11:54:25

Neal Becker skrev:
> I'm a bit confused.
> 
> I'm working with blitz++.  It has
> 
> template<typename T, int N> class Array ...
> 
> which already has a begin(), end(), but I can't use them.  I'm specializing
> boost::begin,end,etc to hide them (I don't want to modify the blitz Array
> class)
> 
> If I specialize range_begin:
> 
> namespace boost {
>   
>   template<typename T, int N>
>   inline typename blitz::array_iterator< blitz::Array<T,N> >::type
> range_begin (blitz::Array<T,N> & a) {
>     return blitz::range_begin (a);
>   }
> }
> 
> Then this doesn't work, it seems that boost::begin (blitz::Array<T,N>&)
> finds the original begin(), but if I do:
> 
> namespace boost {
>   
>   template<typename T, int N>
>   inline typename blitz::array_iterator< blitz::Array<T,N> >::type begin
> (blitz::Array<T,N> & a) {
>     return blitz::range_begin (a);
>   }
> }
> 
> it works as desired.  My questions are:
> 
> 1) Is this reasonable?

Compared to what?

> 2) What is the advantage of using e.g., range_begin() instead of just
> specializing boost::begin()?

i guess that would work too ... I think this is what is done for Shims 
in the STLSoft libs. I can't remember the details of the differences 
between the two approaches, but I'm sure there is a someone on the list 
that can.

I guess the ADL version emplasizes putting stuff in the same interface 
as your class, instead of messing around into another namespace.

-Thorsten