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  1. data Op
  2.     = Change Int -- +, -
  3.     | Move Int   -- >, <
  4.     | OutP       -- .
  5.     | InP        -- ,
  6.     | Loop [Op]  -- [...]
  7.     | Proc [Op]  -- (...)
  8.     | Call       -- :
  9.     deriving (Show, Eq)
  10.  
  11. parse :: String -> [Op]
  12. parse = fst . parseAccum [] Nothing
  13.  
  14. parseAccum :: [Op] -> Maybe Char -> String -> ([Op], String)
  15. parseAccum acc Nothing  ""              = (reverse acc, "")
  16. parseAccum acc (Just x) ""              = error $ "parse error: expected " ++ [x] -- todo
  17. parseAccum acc end          ('+' : src) = parseAccum (Change   1  : acc) end src
  18. parseAccum acc end          ('-' : src) = parseAccum (Change (-1) : acc) end src
  19. parseAccum acc end          ('>' : src) = parseAccum (Move     1  : acc) end src
  20. parseAccum acc end          ('<' : src) = parseAccum (Move   (-1) : acc) end src
  21. parseAccum acc end          ('.' : src) = parseAccum (OutP        : acc) end src
  22. parseAccum acc end          (',' : src) = parseAccum (InP         : acc) end src
  23. parseAccum acc end          (':' : src) = parseAccum (Call        : acc) end src
  24. parseAccum acc end          ('[' : src) = parseAccum (op          : acc) end src' where (op, src') = parseBlock src ']' Loop
  25. parseAccum acc end          ('(' : src) = parseAccum (op          : acc) end src' where (op, src') = parseBlock src ')' Proc
  26. parseAccum acc Nothing      (_   : src) = parseAccum acc Nothing src
  27. parseAccum acc e@(Just end) (c   : src)
  28.     | c == end  = (reverse acc, src)
  29.     | otherwise = parseAccum acc e src
  30.  
  31. parseBlock :: String -> Char -> ([Op] -> Op) -> (Op, String)
  32. parseBlock src end ctor =
  33.     mapFst ctor $ parseAccum [] (Just end) src 
  34.  
  35. mapFst f (x, y) = (f x, y)
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https://ideone.com/1BK0r7
language:
Haskell (ghc 8.4.4)
created:
11 years ago
visibility:
secret

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