:
:  Simple Turing machine program that doubles
:  a unary number.
:
:  Adapted from Roger Penrose's book:
:     The Emperor's New Mind
:
:  You can use any string of consecutive 1s for a
:  test tape and the number of 1s should be doubled.
:

0:0 :0:0:R
0:1:1:0:R
1:0 :10:1:L
1:1:1:1:R
10:0 :11:0:R
10:1:100:0:R
11:0 :0:1:S
11:1:11:1:R
100:0 :101:1:L
100:1:100:1:R
101:0 :10:1:L
101:1:101:1:L