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use number_traits::Num;


#[inline]
pub fn set<'a, 'b, T: Copy + Num>(out: &'a mut [T; 6], m11: T, m12: T, m13: T, m21: T, m22: T, m23: T) -> &'a mut [T; 6] {
    out[0] = m11; out[2] = m21; out[4] = m13;
    out[1] = m12; out[3] = m22; out[5] = m23;
    out
}
#[test]
fn test_set() {
    let mut v = [0, 0, 0, 0, 0, 0];
    set(&mut v,
        1, 2, 3,
        4, 5, 6
    );
    assert!(v == [1, 2, 4, 5, 3, 6]);
}

#[inline]
pub fn zero<'a, 'b, T: Copy + Num>(out: &'a mut [T; 6]) -> &'a mut [T; 6] {
    set(out, T::zero(), T::zero(), T::zero(), T::zero(), T::zero(), T::zero())
}
#[inline]
pub fn identity<'a, 'b, T: Copy + Num>(out: &'a mut [T; 6]) -> &'a mut [T; 6] {
    set(out, T::one(), T::zero(), T::zero(), T::zero(), T::one(), T::zero())
}

#[inline]
pub fn from_mat2<'a, 'b, T: Copy + Num>(out: &'a mut [T; 6], m: &'b [T; 4]) -> &'a mut [T; 6] {
    set(
        out,
        m[0], m[2], T::zero(),
        m[1], m[3], T::zero()
    )
}
#[inline]
pub fn from_mat3<'a, 'b, T: Copy + Num>(out: &'a mut [T; 6], m: &'b [T; 9]) -> &'a mut [T; 6] {
    set(
        out,
        m[0], m[3], T::zero(),
        m[1], m[4], T::zero()
    )
}
#[inline]
pub fn from_mat4<'a, 'b, T: Copy + Num>(out: &'a mut [T; 6], m: &'b [T; 16]) -> &'a mut [T; 6] {
    set(
        out,
        m[0], m[4], m[12],
        m[1], m[5], m[13]
    )
}

#[test]
fn test_from_mat4() {
    let mut m32 = [
        1, 0,
        0, 1,
        0, 0
    ];
    let m4 = [
        1, 0, 0, 0,
        0, 1, 0, 0,
        0, 0, 1, 0,
        2, 2, 0, 1,
    ];
    from_mat4(&mut m32, &m4);
    assert!(m32 == [1, 0, 0, 1, 2, 2]);
}