How to cast simple pointer to a multidimensional-array of fixed size?

user_415616 0
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I have a function that takes a pointer to a floating point array. Based on other conditions, I know that pointer is actually pointing to a 2x2 OR 3x3 matrix. (in fact the memory was initially allocated as such, e.g. float M[2][2] ) The important thing is I want to make this determination in the function body, not as the function argument.

void calcMatrix( int face, float * matrixReturnAsArray )
{
    // Here, I would much rather work in natural matrix notation
    if( is2x2 )
    {
        // ### cast matrixReturnAsArray to somethingAsMatrix[2][2]
        somethingAsMatrix[0][1] = 2.002;
        // etc..
    }
    else if(is3x3)
    { //etc...
    }

}

I am aware that I could use templates and other techniques to better address this problem. My question is really about how to make such a cast at the ### comment. Working in C++.

multidimensional-array matrix casting c c++
4 Answers

If I am right:
typedef float Matrix_t[2][2];
Matrix_t &matrix = *(Matrix_t *)matrixReturnAsArray;
or
float (&matrix2)[2][2] = *(float ( *)[2][2])matrixReturnAsArray;

In C there is only the way with the pointer
Matrix_t *someThingAsMatrix = (Matrix_t *)matrixReturnAsArray;
and access via:
(*someThingAsMatrix)[1][0] = ...

user_194363660
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