source 1998 Hasegawa--Nakajima--Matsui, page 188
parameter half
assume half*2=1
compute R1 = X1
compute R2 = Y1
compute R3 = Z1
compute R4 = R3^2
compute R3 = R2 R3
compute R3 = 2 R3
compute R4 = R4^2
compute R4 = a R4
compute R5 = R1^2
compute R4 = R4+R5
compute R5 = 2 R5
compute R4 = R4+R5
compute R2 = 2 R2
compute R2 = R2^2
compute R5 = R2^2
compute R5 = half R5
compute R2 = R2 R1
compute R1 = R4^2
compute R1 = R1-R2
compute R1 = R1-R2
compute R2 = R2-R1
compute R2 = R2 R4
compute R2 = R2-R5
compute X3 = R1
compute Y3 = R2
compute Z3 = R3