Re: [Boost-users] [non Boost] Template troubles.

Subject: Re: [Boost-users] [non Boost] Template troubles.
From: Noah Roberts (roberts.noah_at_[hidden])
Date: 2008-12-12 12:52:45

Noah Roberts wrote:

> In int const x[5][5], the int contained within the dual array is the 
> constant.  In the case of T const& value[] though it is T that is const, 
> which is an array.  This is nonsense I believe (arrays are always 
> r-values).  VS seems to have no way to handle it while the others do.

I think this is a bug in VS.

At first I thought that what I was doing and what you are doing where 
different because you had a typedef int[size][size] that you later 
declare a const object of.  I thought maybe this actually made the 
*array* const but I was mistaken.  The standard quite clearly states, 
with example, that even when you are doing that to a typedef of array 
type...the const applies to the elements, not to the array.  The 
provided example from 8.3.4/1:

typedef int A[5], AA[2][3];
typedef const A CA;        // type is "array of 5 const int"
typedef const AA CAA;      // type is "array of 2 array of 3 const int"

It doesn't get less ambiguous than that.

That means, to me, that even when T is an array type, expecting a const 
reference of that type should resolve in the same manner and your 
template should resolve.  As someone mentioned in comp.lang.c++ your 
second version (the one expecting an array) is a closer match and should 
be the one used.

I think there's a bug in msvc in template typing.  I'd bet that it's 
considering const T (&ref)[size] to be an /array of const array of int/ 
when passed an /array of array of const int/, which is nonsense in C++ 
and would never resolve to anything.