Nat. func (m *Modulus) Nat() *Nat { // Make a copy so that the caller can't modify m.nat or alias it with // another Nat in a modulus operation. n := NewNat() n.set(m.nat) return n } // shiftIn calculates x = x << _W + y mod m. // // This assumes that x is already reduced mod m. // //go:norace func (x *Nat) shiftIn(y uint, m *Modulus) *Nat { d := NewNat().resetFor(m) // Eliminate bounds checks in the loop. size := len(m.nat.limbs) xLimbs := x.limbs[:size] dLimbs := d.limbs[:size] mLimbs := m.nat.limbs[:size]...