hello,
we can define a array by following code:
     int a[8];
then, what is the type of a?
when we use template , can we use array as a class to generate a new
class .
for example:
     std::vector<a[] > CArrayVetor or we must do it in other way?

thanks



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> we can define a array by following code:
>      int a[8];
> then, what is the type of a?
> when we use template , can we use array as a class to generate a new
> class .
> for example:
>      std::vector<a[] > CArrayVetor or we must do it in other way?


The name 'a' in your example has type int[8]; (array of 8 int's).
Therefore, the following code for computing any array's size works:

   template< typename T, size_t N >
   size_t Size( T(&array)[N] )  // reference to array of N elements
of type T
   {
       return N;
   }

However an array is a special type in many ways. For example it
doesn't have an assignment operator. Therefore the following function
doesn't work:

   template< typename T, size_t N >
   void assign1( T(&lhs)[N], T(&rhs)[N] )
   {
       lhs = rhs;
   }

Similarly, if you define the following function:

   template< typename T >
   void assign2( T & lhs, T & rhs )
   {
       lhs = rhs;
   }

It will work for many types, but not for 'a' from your example,
because 'a' is an array and thus doesn't have an assignment operator.

std::vector< int(&)[8] > will not work because int(&)[8] is a
reference and you cannot store references in vector, as reference have
no storage an do not have assignment operator.

std::vector< int[8] > will not work either because arrays (as opposed
to references to arrays) decay to pointers and you will be handling
std::vector< int*> in the end.

If there is a reason you really needed to use a vector of arrays, you
could consider using
   std::vector< std::vector<int> >
or
   std::vector< boost::array<int> >
or perhaps you need some matrix type.

Regards,
&rzej


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