4-level stack manipulation on 12c

[Mark Hardman]

(03-02-2015 03:18 AM)Don Shepherd Wrote:  If my 4-level stack on my 12c contains:

t - don't care
z - don't care
y - 17
x - 5

and I want it to contain:

t - 17
z - 5
y - 17
x - 5

is there an elegant way to achieve that using only ENTER, roll down, and x<->y?

If you also allow Rup it can be done in six steps:

Code:


Enter, Enter, Rup, Enter, Rdn, x<>y

t   0    0   17    5    5   17   17
z   0   17    5    5    5    5    5
y  17    5    5    5   17    5   17
x   5    5    5   17   17   17    5

The Rup can be replaced with three Rdn for a total of eight steps:

Code:


Enter, Enter, Rdn, Rdn, Rdn, Enter, Rdn, x<>y

t   0    0   17    5    5    5    5   17   17
z   0   17    5   17    5    5    5    5    5
y  17    5    5    5   17    5   17    5   17
x   5    5    5    5    5   17   17   17    5

I'm sure someone can do better.