; This TM decides the language { a^n b^n c^n }.
; It is based on the JFLAP example "anbncn-TM.jff" (simplified a bit).
;
; This is a decider: it should halt for every input string in {a,b,c}*.
; A computation accepts if it ends in the state "halt-accept".
; We do not use an explicit "halt-reject" state. Instead, computations
; reject with an implicit halt (no rule for current state and symbol).
;
; Example accepted inputs: '', abc, aabbcc, aaabbbccc
; Example rejected inputs: aabc, abbc, abcc, acb, cba

; First jump from 0 (start state) to q0 (start state of JFLAP example)
0 * * * q0

; q0: start at left, either accept empty string, or erase first a
q0 a _ r q1
q0 _ _ * halt-accept
q0 # # r q7
; q1: skip remaining a's and #'s, replace first b with #
q1 a a r q1
q1 # # r q2
q1 b # r q3
; q2: replace first b after skipping any #'s
q2 # # r q2
q2 b # r q3
; q3: skip remaining b's until first c
q3 b b r q3
q3 c c r q4
; q4: skip c's until first blank
q4 c c r q4
q4 _ _ l q5
; q5: erase the last c, step left and goto q6
q5 c _ l q6
; q6 run left to first blank, then goto q0 for the next loop
q6 # # l q6
q6 a a l q6
q6 b b l q6
q6 c c l q6
q6 _ _ r q0
; q7: check the remaining string is entirely #'s, if so accept
q7 # # r q7
q7 _ _ l halt-accept