std::array instantiation error

Question

Embarrassingly simple problem here. I am trying to use std::array and am tripping at the first hurdle with the error ...

implicit instantiation of undefined template 'std::__1::array<char,10>'

The code that gives the error is shown below. I can work around it with std::map for now, but I'm sure the fix must be simple!!

enum  p_t   {
    EMPTY = 0
    ,BORDER_L
    // ...
    ,BORDER_BR
    ,DATUM
    ,NUMEL    };

class PlotChars
{
    array<char, p_t::NUMEL> charContainer;
    // error on this ^ line:
    //   implicit instantiation of undefined template 'std::__1::array<char,10>'
};

Answer 1

My first guess would be that you simply forgot to:

#include <array>

...before trying to use the array template. While you can (at least indirectly) use a few classes without including the headers (e.g., the compiler can create an std::initializer_list from something like {1, 2, 3} without your including any headers) in most cases (including std::array) you need to include the header before using the class template.

Answer 2

You are using a C-style enum, so you probably need to omit the enum name, if your compiler isn't fully C++11 compliant.

array<char, NUMEL> charContainer;

This works on gcc 4.4.3, whereas the equivalent to your code does not yet work on that version (but does on later ones)

#include <array>

enum XX { X,Y,Z };

struct Foo
{
  std::array<char, Y> a;
};

int main()
{
  Foo f;
}