how to return a matrix?



  • hey 🙂
    i try to return a matrix from a function I have tried many ways unfortunately it doesn’t work there is my code:
    float** toMatrix() {
    float mat[3][3]; float a ; float b ; float c ; float d ;

    a=R; b=I; c=J; d=K;

    mat[0][0]= a*a+b*b-c*c-d*d; mat[0][1]= 2*(b*c-a*d); mat[0][2]= 2*(a*c+b*d);

    mat[1][0]= 2*(b*c+a*d); mat[1][1]= a*a-b*b+c*c-d*d; mat[1][2]=2*(c*d-a*b);

    mat[2][0]= 2*(b*d-a*c); mat[2][1]=2*(a*b+c*d); mat[2][2]=a*a-b*b-c*c+d*d;

    return mat;

    }

    and i have this when i try to compile " error: cannot convert 'float (*)[3]' to 'float**' in return
    return mat;"
    have anyone an idea of how can i do this?
    thanks
    ^



  • std::array<std::array<float, 3>, 3> mat;
    

    Also use this type as the return type. Or you could write a matrix class and use that.

    Even if your code would work like you inteded to, it would be undefined behaviour.


  • Mod

    In general: A pointer is not an array and an array is not a pointer.

    Corollary: A pointer to a pointer is not a pointer to an array and neither of those is a 2D-array, and vice versa.

    This is not just a syntactic difference. The actual data layout in memory is totally different.

    But, as patrick246 explained, it is unusual to work with raw pointers and arrays in C++ anyway.


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