TODO

add generator back to input to compare optimisation
optimisation
- move as many clauses as possible to the front: 1 + (2 + 3) => (1 + 2) + 3
- remove*0 and *1, +0 and -0, /1
use LXI to set register pairs at once
add bitshifts and bitwise operators
- optimise *2 to << 1 and /2 to >> 1