Turing Machine to double a string containing the alphabet [A,B,0] accessible via http://turingmachine.ioturingmachine.io/?import-gist=f178efe88f5e64dd431c596b3a69bd39

StringDoubler.yaml

name: StringDoubler
source code: |
  # Adds 1 to a binary number.
  input: 'ABBA00000000000000'
  blank: ' '
  start state: q0
  table:
    # scan to the rightmost digit
    q0:
      A : {write: 0, R: q1}
      B : {write: 0, R: qB}
    q1:
      [B, A] : R
      0 : {R: q2}
    q2:
      B : R
      A : R
      0 : {write: A, L: q4}
    q4:
      B : L
      A : L
      0 : {L: q5}
    q5:
      B : L
      A : L
      0 : {write: A, R: q0}
    qB:
      [B, A] : R
      0 : {R: qC}
    qC:
      B : R
      A : R
      0 : {write: B, L: qE}
    qE:
      B : L
      A : L
      0 : {L: qF}
    qF:
      B : L
      A : L
      0 : {write: B, R: q0}
    done:
positions:
  q0: {x: 379.4, y: 256, fixed: false}
  q1: {x: 247.77, y: 332.31, fixed: false}
  q2: {x: 391.88, y: 357.34, fixed: false}
  q4: {x: 278.5, y: 258.08, fixed: false}
  q5: {x: 320.47, y: 397.26, fixed: false}
  qB: {x: 319.6, y: 118.72, fixed: false}
  qC: {x: 423.38, y: 21.03, fixed: false}
  qE: {x: 550.76, y: 89.01, fixed: false}
  qF: {x: 527.74, y: 230.14, fixed: false}
  done: {x: 568.91, y: 441.08, fixed: false}