36 lines
1007 B
Haskell
36 lines
1007 B
Haskell
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{-# LANGUAGE BangPatterns #-}
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import Data.IntMap.Strict (IntMap, findWithDefault, insert, empty)
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type Tape = IntMap Int
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type Step = (Tape, Int, State)
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data State = State {
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zeroVal :: Int,
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oneVal :: Int,
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zeroPos :: Int,
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onePos :: Int,
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zeroState :: State,
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oneState :: State
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}
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a, b, c, d, e, f :: State
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a = State 1 0 1 (-1) b e
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b = State 1 0 (-1) 1 c a
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c = State 1 0 (-1) 1 d c
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d = State 1 0 (-1) (-1) e f
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e = State 1 1 (-1) (-1) a c
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f = State 1 1 (-1) 1 e a
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step :: Step -> Step
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step (tape, position, (State zval oval zpos opos zstate ostate)) =
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case findWithDefault 0 position tape of
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0 -> (insert position zval tape, position + zpos, zstate)
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1 -> (insert position oval tape, position + opos, ostate)
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stepN :: Int -> Step -> Step
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stepN 0 s = s
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stepN n s = let !nextStep = step s in stepN (n - 1) nextStep
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main :: IO ()
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main = do
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let (tape, _, _) = stepN 12386363 (empty, 0, a)
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print $ foldr (+) 0 tape
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