Function sprs::binop::add_mat_same_storage

pub fn add_mat_same_storage<N, I, Mat1, Mat2>(
    lhs: &Mat1, 
    rhs: &Mat2
) -> CsMatI<N, I> where
    N: Num + Copy,
    I: SpIndex,
    Mat1: SpMatView<N, I>,
    Mat2: SpMatView<N, I>, 

Sparse matrix addition, with matrices sharing the same storage type