Coding Practice - Float* -> Vector3* cast

If you were given the following:

#include 

struct vec {
    float x,y,z;
    vec(float x, float y, float z) : x(x), y(y), z(z) {}
};

int main() {
    float verts[] = {1,2,3,4,5,6,7,8,9}; // length guaranteed to be a multiple of 3
    assert(sizeof(vec) == sizeof(float) * 3);

    // Option 1
    for (int i = 0; i (verts)[i];
        // ...
    }

    // Option 2
    for (int i = 0; i < 9; i += 3) {
        vec a(verts[i], verts[i+1], verts[i+2]); // -O3 averts the copy, so d/w
        // ...
    }

    return 0;
}

Which is considered better practice?

The advantage to the latter option is of course far more explicit, and carries all the advantages/disadvantages that contains; but may not be portable depending on the assertions you can make.

I would go with a 3rd option that is closest to option 2. But instead of taking the three parameters separately in the constructor, take an array of floats.

struct vec {
    float x,y,z;
    vec(float fv[]) : x(fv[0]), y(fv[1]), z(fv[2]) {}
};

int main() {
    float verts[] = {1,2,3,4,5,6,7,8,9};

    for (int i = 0; i < 9; i += 3) {
        const vec a(&verts[i]);
        // ...
    }

    return 0;
}

StackExchange Code Review Q#4384, answer score: 3