// b_add1.tm  given a binary number on input tape, add 1 to that number
//  input must have leading 0
//  The basic algorithm is to look backwards from input
//  if lowest bit, first in backwards scan is 0, set to 1, done
//  if 1 set to 0 and continue bacwards scan

start s
halt  f
trace all

s   0   s  ##  R      move right to end "#]"
s   1   s  ##  R      move right to end "#]"
s   #]  a  ##  L      found end, go to state a
a   0   f  1   L      done
a   1   c  0   L      add and carry
c   0   f  1   L      done
c   1   c  0   L      done if input has leading zero
// c   1   d  0   L
// c   #[  f  1   R
// d   #[  f  1   R
// d   0   f  1   L
// d   1   d  0   L

enddef

tape 0
tape 01
tape 00
tape 011
tape 0101