a.go

// Exp sets z = x**y mod |fm|
func (z *Fq) Exp(x, y *Fq) *Fq {
	load(z)

	if y.abs.Cmp(bigZero) == 0 {
		return z.SetInt64(0)
	} else if y.abs.Cmp(bigOne) == 0 {
		return z
	} else if new(big.Int).Mod(y.abs, big.NewInt(2)).Cmp(bigZero) == 0 {
		t := new(Fq).Div(y, NewField(2))
		z.Mul(x, x).Exp(z, t)
	} else {
		z.Mul(x, x)
		t := new(Fq).Div(y, NewField(2))
		z.Exp(z, t)
		z.Mul(z, x)
	}
	return z
}