g++ member function .at() for arrays

[Robin Whittle]

I am a newbie to this list.  Thanks for GCC, g++ the C++ standard
library and GDB!  Apologies in advance if I have missed a web page where
this question is answered.  Perhaps this question belongs on the
libstdc++ list.

With g++ 4:4.7.2-1 and libstdc++6 4.7.2-4, installed on 64 bit Debian,
using the -std=c++11 compiler option, I attempted to compile code such as:

  aa1.at(1) = aa1.at(2) + aa1.at(3);
  cout << aa1.size() << endl;

where aa1 is an array of ints.  The error message was:

   error: request for member 'at' in 'aa1', which is of
   non-class type 'int [4]'.

Yet these lines for vectors and deques:

  vv1.at(1) = vv1.at(2) + vv1.at(3);
  dd1.at(1) = dd1.at(2) + dd1.at(3);

compiled and worked fine.  Both of these lines were implemented with
bounds checking.


According to my understanding of the near-final draft standard
n3242-1.pdf, page 729, in the last item of Table 101, the member
function at() should provide bounds checked access to:

  basic_string, string, array, deque and vector.

As far as I can tell, this does not work for arrays in 4.7.2.  Am I
missing a compiler option?

I think the .at() member function should apply to arrays, according to:

  http://en.cppreference.com/w/cpp/container/array/at

and page 265 of N. M. Josuttis "The C++ Standard Library 2nd Ed.".

I couldn't see specific mention of this at:


http://gcc.gnu.org/onlinedocs/gcc-4.7.2/libstdc++/manual/manual/status.html#status.iso.2011

other than the line:

  23.2.3  Sequence containers  Y


I am not sure if this functionality would be in g++ or libstdc++ or both
and I am not sure where to look in the documentation to see if it is or
will be implemented.  I didn't make any progress Googling for the
compiler error text or for any relevant terms I could think of.

Thanks again for GCC!

  - Robin

Re: g++ member function .at() for arrays

[Robin Whittle]

Further to my previous message, the start of my program is:

#include 
#include 

#include 
#include 
#include 

using std::vector;
using std::deque;
using std::cout;
using std::endl;

int main(int argc, char **argv)
{
   int aa1[4] = {0, 1, 2, 3};
   vector vv1{50, 51, 52, 53};
   deque dd1{100, 101, 102, 103};


  - Robin