int32 { x := int32(fieldFromMontgomery(r)) // x <= q / 2 ? x : x - q return constantTimeSelectLe(x, q/2, x, x-q) } // fieldInfinityNorm returns the infinity norm ||r||∞ of r, or the absolute // value of r centered around 0. func fieldInfinityNorm(r fieldElement) uint32 { x := int32(fieldFromMontgomery(r)) // x <= q / 2 ? x : |x - q| // |x - q| = -(x - q) = q - x because x < q => x - q < 0 return uint32(constantTimeSelectLe(x, q/2, x, q-x)) } // fieldReduceOnce reduces a value a < 2q. func fieldReduceOnce(a...