Re: add inner const to arrays T[]...[]
On 2011-12-12 02:47, Lorenzo wrote:
I would like to write a metafunction to add const to array types T
[]...[]. Something like this:
template< typename T>
struct add_inner_const {
typedef typename add_const<T>::type type;
};
What is template add_const supposed to be in this example? Is this
std::add_const? If yes, why are you not using it instead of reinventing
the wheel?
template< typename T>
struct add_inner_const< T[2][3]> {
typedef T const type[2][3];
};
But I can program it without specifying 2 and 3? Otherwise, I have to
program a tons of specializations for all possible indexes 2, 3, etc.
Sure that is possible, but I'm not really sure what you want to realize.
Why does std::add_const not work for you? It should also ensure that
given any array type of element type E, the result is an array type of
element type const E. If you don't have a corresponding library
implementation available, the following should work for you:
template<class T>
struct add_const {
typedef const T type;
};
If for some reasons you only want to capture array types you can use a
partial specialization:
template<typename T>
struct add_inner_const;
template<typename T, std::size_t N>
struct add_inner_const<T[N]> {
typedef T const type[N];
};
This will properly handle array of any (known) dimension and rank.
Array types have the special property that there is no difference
between an array of const T and a const array type of T.
HTH & Greetings from Bremen,
Daniel Kr?gler
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