// lanbncn.tm
// accept the language L = { a^n b^n c^n | n>0 }    not a CFL
//
// method: scan left to right, on each pass convert
//         one "a" to "X", one "b" to "Y" and one "c" to "Z"
//         reject if any "b" or "c" is missing
//         accept if no more "a" "b" or "c"
  
final q6
start q0
limit 100

q0  a  q1  X  R   convert left most "a" to "X"
q0  Y  q4  Y  R   no more a's  do check for only Y's and Z's

q1  a  q1  a  R   skip over a's and Y's
q1  Y  q1  Y  R
q1  b  q2  Y  R   convert left most "b" to "Y"

q2  b  q2  b  R   skip over b's and Z's
q2  Z  q2  Z  R
q2  c  q3  Z  L   convert left most "c" to "Z"

q3  a  q3  a  L   back up over a's, b's, Y's and Z's, stop on first "X"
q3  b  q3  b  L
q3  Y  q3  Y  L
q3  Z  q3  Z  L
q3  X  q0  X  R   ready for next pass

q4  Y  q4  Y  R   skip over Y's, must find Z
q4  Z  q5  Z  R

q5  Z  q5  Z  R   skip over Z's
q5  #] q6  ## N   end of input, no b's or c's left to get here, accept

q6  #] q6 // done this is the final state

enddef

tape  abc        accept
tape  bac        reject
tape  bb         reject
tape  aa         reject
tape  cc         reject
tape  aabc       reject
tape  abbc       reject
tape  abcc       reject
tape  aaabbbccc  accept