// One sets v = 1, and returns v.
func (v *Element) One() *Element {
	*v = *feOne
	return v
}

// reduce reduces v modulo 2^255 - 19 and returns it.
func (v *Element) reduce() *Element {
	v.carryPropagate()

	// After the light reduction we now have a field element representation
	// v < 2^255 + 2^13 * 19, but need v < 2^255 - 19.

	// If v >= 2^255 - 19, then v + 19 >= 2^255, which would overflow 2^255 - 1,