From 440dd38f24d1df150fb5b4c7965bb6e792c929fe Mon Sep 17 00:00:00 2001
From: Ray Hogenson <rhogenson@posteo.net>
Date: Sat, 7 Sep 2019 16:36:01 -0700
Subject: Write a little guy

This program is in a weird state right now, but I'm checking it in to
git so that I can back it up, since I want to reinstall again.
---
 BrainFuck.hs | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 BrainFuck.hs

(limited to 'BrainFuck.hs')

diff --git a/BrainFuck.hs b/BrainFuck.hs
new file mode 100644
index 0000000..aa724b8
--- /dev/null
+++ b/BrainFuck.hs
@@ -0,0 +1,123 @@
+{-# LANGUAGE FlexibleInstances #-}
+module BrainFuck (runBF, BF(..), strToBF) where
+
+import qualified Data.Sequence as Sequence
+import Data.Foldable (toList)
+import qualified System.Random as Random
+import qualified Evolve
+import RandomState (splitG)
+import qualified Control.Monad.State as State
+import System.IO.Unsafe (unsafePerformIO)
+import Control.Concurrent (yield)
+import qualified EditDistance
+import Data.List (intercalate)
+
+data BF = Plus | Minus | ML | MR | Print | Loop [BF] deriving Eq
+
+instance Show BF where
+  show Plus = "+"
+  show Minus = "-"
+  show ML = "<"
+  show MR = ">"
+  show Print = "."
+  show (Loop bf) = '[' : intercalate "" (map show bf) ++ "]"
+
+mutateString :: Random.RandomGen g => String -> State.State g String
+mutateString [] = do r <- fst . Random.random <$> splitG
+                     if r < Evolve.mutateProbability
+                       then (: []) . fst . Random.randomR ('+', ']') <$> splitG
+                       else return []
+mutateString (x : xs) = do i <- insert
+                           d <- delete
+                           r <- rest
+                           return $ i ++ d ++ r
+  where insert = do r <- fst . Random.random <$> splitG
+                    if r < Evolve.mutateProbability
+                      then (: []) . fst . Random.randomR ('+', ']') <$> splitG
+                      else return []
+        delete = do r <- fst . Random.random <$> splitG
+                    if r < Evolve.mutateProbability
+                      then return []
+                      else return [x]
+        rest = mutateString xs
+
+instance Evolve.Evolvable [BF] where
+  mutate bf = BrainFuck.strToBF <$> mutateString (intercalate "" (map show bf))
+  score bf = 100 - fromIntegral (EditDistance.dist (BrainFuck.runBF bf) "Hello World!")
+
+randomBF :: Random.RandomGen g => State.State g BF
+randomBF = do r <- fst . Random.randomR (0, 5 :: Int) <$> splitG
+              case r of
+                0 -> return Plus
+                1 -> return Minus
+                2 -> return ML
+                3 -> return MR
+                4 -> return Print
+                _ -> Loop <$> Evolve.mutate []
+
+instance Random.Random BF where
+  -- TODO: may as well have a correct implementation here
+  randomR _ _ = undefined
+  random g = State.runState randomBF g
+
+extend :: a -> Int -> Sequence.Seq a -> Sequence.Seq a
+extend def i s
+  | i < length s = s
+  | otherwise = s Sequence.>< Sequence.replicate (i - length s + 1) def
+
+safeAdjust :: a -> (a -> a) -> Int -> Sequence.Seq a -> Sequence.Seq a
+safeAdjust def f i s = Sequence.adjust f i (extend def i s)
+
+iAdj :: Num a => (a -> a) -> Int -> Sequence.Seq a -> Sequence.Seq a
+iAdj = safeAdjust 0
+
+safeIndex :: a -> Sequence.Seq a -> Int -> a
+safeIndex def s i = (extend def i s) `Sequence.index` i
+
+iInd :: Num a => Sequence.Seq a -> Int -> a
+iInd = safeIndex 0
+
+safeEnumToChar :: Enum e => e -> Char
+safeEnumToChar e = toEnum $ i `mod` (fromEnum '~' - spc + 1) + spc
+  where i = fromEnum e
+        spc = fromEnum ' '
+
+runBF :: [BF] -> String
+runBF bf = let (_, _, s) = foldl go (Sequence.singleton 0, 0, Sequence.empty) bf
+           in toList s
+  where go :: (Sequence.Seq Integer, Int, Sequence.Seq Char) -> BF
+           -> (Sequence.Seq Integer, Int, Sequence.Seq Char)
+        go (a, dp, s) Plus = (iAdj succ dp a, dp, s)
+        go (a, dp, s) Minus = (iAdj pred dp a, dp, s)
+        go (a, dp, s) ML = (a, max (pred dp) 0, s)
+        go (a, dp, s) MR = (a, succ dp, s)
+        go (a, dp, s) Print = (a, dp, s Sequence.|> safeEnumToChar (a `iInd` dp))
+        go st@(a, dp, _) cmd@(Loop inner)
+          | 0 <- a `iInd` dp = st
+          | otherwise = unsafePerformIO yield `seq` go (foldl go st inner) cmd
+
+strToBF' :: String -> ([BF], String)
+strToBF' [] = ([], [])
+strToBF' ('[':ss) =
+ case strToBF' ss of
+  (bf, ']':rest) -> let (bf', extra) = strToBF' rest
+                    in (Loop bf : bf', extra)
+  -- Failure case, but we tolerate it
+  (bf, rest) -> ([Loop bf], rest)
+strToBF' rest@(']':_) = ([], rest)
+strToBF' (x:ss)
+  | Just cmd <- conv x = let (bf, extra) = strToBF' ss
+                         in (cmd : bf, extra)
+  | otherwise = strToBF' ss
+
+conv :: Char -> Maybe BF
+conv '+' = Just Plus
+conv '-' = Just Minus
+conv '<' = Just ML
+conv '>' = Just MR
+conv '.' = Just Print
+conv _ = Nothing
+
+strToBF :: String -> [BF]
+strToBF s = let (bf, _) = strToBF' s
+            in bf
-- 
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