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# Undeclared identifier in derived class - but declared protected?

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Substantially cut down code: Matrix.h
#ifndef MATRIX_H
#define MATRIX_H

#include <algorithm>
#include <stdexcept>

namespace Maths
{
namespace impl
{
static const char AT_DOMAIN_MSG[] = "Index must be non-negative and less than or equal to the relevant dimension template parameter.";
}

template <unsigned height_, unsigned width_> class Matrix
{
protected:
float elems[height_ * width_];

public:
static const unsigned height = height_;
static const unsigned width = width_;

Matrix()                               { std::fill(elems, elems + height * width, 0.0f); }
Matrix(float (&elems)[height * width]) { std::copy(elems, elems + height * width, this->elems); }
};

typedef Matrix<4, 4> Matrix44;
typedef Matrix<3, 3> Matrix33;
}

#endif


Vector.h
#ifndef VECTOR_H
#define VECTOR_H

#include <cmath>
#include "Matrix.h"

namespace Maths
{
template <unsigned dimension_> struct Vector : Matrix<dimension_, 1>
{
static const unsigned dimension = dimension_;

Vector(const Matrix<dimension, 1>& v)
: Matrix<dimension, 1>(v)
{}

float operator[](int index) const
{
if (index >= dimension || index < 0)
throw std::domain_error(impl::AT_DOMAIN_MSG);

/* !!! ERROR HERE !!! - elems undeclared identifier? */
return elems[index];
}
};

struct Vector3 : Vector<3>
{
float  x() const { return operator[](0); }
float  y() const { return operator[](1); }
float  z() const { return operator[](2); }

Vector3(const Matrix<3, 1>& v)
: Vector(v)
{}
};
}

#endif


Error is that elems in Vector.h is apparently undeclared. What am I doing wrong? The error disappears if I don't disable language extensions (MSVC++ 2008EE), but that's not really a solution. Is there a way to get VS to tell you when it's using an extension?

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use return this->elems[index];
Here is a post in which I enquired about it a while ago.
http://www.gamedev.net/community/forums/topic.asp?topic_id=443946

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I'm going to write this quickly and move on so my head doesn't explode from how dumb C++ is in certain regards. elems is a dependent name, and hence will not be looked up unless its scope is explicitly qualified. Qualify elems to be a member of Matrix, and it should succeed. STUPID STUPID AARGH sorry gotta go

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Quote:
 Original post by SneftelI'm going to write this quickly and move on so my head doesn't explode from how dumb C++ is in certain regards. elems is a dependent name, and hence will not be looked up unless its scope is explicitly qualified. Qualify elems to be a member of Matrix, and it should succeed. STUPID STUPID AARGH sorry gotta go

Haha, thanks!

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