should go in the case, fill in the values of "left" variables,
and initialize the values of other non-left variable to zero
or spaces. Then, when we're done with that case, we have to
save the values of "left" variables to copy into the next case
should go in the case, fill in the values of "left" variables,
and initialize the values of other non-left variable to zero
or spaces. Then, when we're done with that case, we have to
save the values of "left" variables to copy into the next case