Function igraph_sparsemat_add 

pub unsafe extern "C" fn igraph_sparsemat_add(
    A: *const igraph_sparsemat_t,
    B: *const igraph_sparsemat_t,
    alpha: igraph_real_t,
    beta: igraph_real_t,
    res: *mut igraph_sparsemat_t,
) -> igraph_error_t