module exercises

import StdEnv
import TuringMachines

Start :: *World -> *World
Start w
# (io,w)    = stdio w
# m         = initTuringMachine ex_9_4 tape_9_4
# io        = fwrites (toString m +++ "\n") io
# io        = loop m io
# (ok,w)    = fclose io w
| not ok    = abort "Couldn't close stdio\n"
| otherwise = w
where
    loop m f
    # m         = step m
    # f         = fwrites (toString m +++ "\n") f
    | m.running == Running = loop m f
    | otherwise = f

tape_9_3_b = [Just c \\ c <- fromString "abbaba"]
ex_9_3_b :: TuringMachine Char
ex_9_3_b = { alphabet = ['a', 'b', 'X', 'Y'],
             inputs = ['a', 'b'],
             transition = f }
where
    f :: Int (Maybe Char) -> TuringMachineMove Char
    f 0 Nothing     = Step 1 Nothing    Right

    f 1 (Just 'a')  = Step 1 (Just 'a') Right
    f 1 (Just 'b')  = Step 1 (Just 'b') Right
    f 1 c           = Step 2 c          Left

    f 2 Nothing     = Step 6 Nothing    Right
    f 2 (Just 'a')  = Step 3 (Just 'X') Right
    f 2 (Just 'b')  = Step 4 (Just 'Y') Right

    f 3 (Just c)    = Step 3 (Just c)   Right
    f 3 Nothing     = Step 5 (Just 'a') Left

    f 4 (Just c)    = Step 4 (Just c)   Right
    f 4 Nothing     = Step 5 (Just 'b') Left

    f 5 (Just c)    = Step 5 (Just c)   Left
    f 5 Nothing     = Step 1 Nothing    Right

    f 6 (Just 'X')  = Step 6 (Just 'a') Right
    f 6 (Just 'Y')  = Step 6 (Just 'b') Right
    f 6 (Just c)    = Step 6 (Just c)   Left

    f _ _           = Halt

tape_9_3_c = [Just c \\ c <- fromString "abbaa"]
ex_9_3_c :: TuringMachine Char
ex_9_3_c = { alphabet = ['a', 'b', 'X'],
             inputs = ['a', 'b'],
             transition = f }
where
    f :: Int (Maybe Char) -> TuringMachineMove Char
    f 0 Nothing     = Step 1 Nothing    Right

    f 1 (Just 'a')  = Step 1 (Just 'a') Right
    f 1 (Just 'b')  = Step 1 (Just 'b') Right
    f 1 (Just 'X')  = Step 2 (Just 'X') Left
    f 1 Nothing     = Step 2 (Just 'X') Left

    f 2 (Just 'a')  = Step 3 (Just 'X') Right
    f 2 (Just 'b')  = Step 4 (Just 'X') Right
    f 2 Nothing     = Step 5 Nothing    Left

    f 3 (Just 'X')  = Step 2 (Just 'a') Right
    f 3 Nothing     = Step 2 (Just 'a') Right

    f 4 (Just 'X')  = Step 2 (Just 'b') Right
    f 4 Nothing     = Step 2 (Just 'b') Right

    f 5 (Just 'a')  = Step 6 (Just 'a') Left
    f 5 (Just 'b')  = Step 6 (Just 'b') Left

    f 6 (Just 'X')  = Step 5 (Just 'X') Left
    f 6 (Just 'a')  = Step 2 (Just 'a') Right
    f 6 (Just 'b')  = Step 2 (Just 'b') Right
    f 6 Nothing     = Step 7 Nothing    Right

    f 7 (Just c)    = Step 7 (Just c)   Right
    f 7 Nothing     = Step 8 Nothing    Left

    f 8 (Just 'X')  = Step 8 Nothing    Left
    f 8 (Just c)    = Step 8 (Just c)   Left

    f _ _           = Halt

tape_9_4 = [Just c \\ c <- fromString "babaabbaaacabababb"]
ex_9_4 :: TuringMachine Char
ex_9_4 = { alphabet = ['a', 'b', 'c'],
           inputs = ['a', 'b', 'c'],
           transition = f }
where
    f :: Int (Maybe Char) -> TuringMachineMove Char
    f 0 Nothing     = Step 1 Nothing    Right

    f 1 (Just 'a')  = Step 2 (Just 'a') Right
    f 1 c           = Step 1 c          Right

    f 2 (Just 'a')  = Step 3 (Just 'a') Right
    f 2 c           = Step 1 c          Right

    f 3 (Just 'a')  = Step 4 (Just 'a') Right
    f 3 c           = Step 1 c          Right

    f 4 (Just 'a')  = Step 4 (Just 'a') Right
    f 4 (Just 'c')  = Step 5 (Just 'c') Left
    f 4 c           = Step 1 c          Right

    f 5 (Just c)    = Step 5 (Just c)   Left

    f _ _           = Halt