mod.rs

// omg
fn true_mod<T: Copy>(a: T, n: T) -> <<<T as ops::Rem>::Output as ops::Add<T>>::Output as ops::Rem<T>>::Output
    where T: ops::Add + ops::Rem,
          <T as ops::Rem>::Output: ops::Add<T>,
          <<T as ops::Rem>::Output as ops::Add<T>>::Output: ops::Rem<T>
{
    (((a % n) + n) % n)
}