never executed always true always false

    1 module HelVM.HelMA.Automata.BrainFuck.Impl.Fast.Parser
    2   ( parseAsList
    3   , parseAsListSafe
    4   , parseWithOptimize
    5   , parseWithOptimizeSafe
    6   ) where
    7 
    8 import           HelVM.HelMA.Automata.BrainFuck.Impl.Fast.Instruction
    9 import           HelVM.HelMA.Automata.BrainFuck.Impl.Fast.Optimizer
   10 
   11 import qualified HelVM.HelMA.Automata.BrainFuck.Common.SimpleInstruction as Simple
   12 
   13 import           HelVM.HelMA.Automaton.API.IOTypes
   14 import           HelVM.HelMA.Automaton.ReadPExtra
   15 
   16 import           HelVM.HelIO.Control.Safe
   17 
   18 import           Control.Applicative.Tools
   19 
   20 import qualified Data.Text                                               as Text
   21 
   22 import           Text.ParserCombinators.ReadP                            hiding ( many )
   23 
   24 parseWithOptimizeSafe ∷ Source → Safe FastInstructionList
   25 parseWithOptimizeSafe = parseWithOptimize
   26 
   27 parseAsListSafe ∷ Source → Safe FastInstructionList
   28 parseAsListSafe = parseAsList
   29 
   30 parseWithOptimize ∷ MonadSafe m ⇒ Source → m FastInstructionList
   31 parseWithOptimize = optimize <.> parseAsList
   32 
   33 parseAsList ∷ MonadSafe m ⇒ Source → m FastInstructionList
   34 parseAsList = runParser parameterizedInstructionsParser . filterComments
   35 
   36 parameterizedInstructionsParser ∷ ReadP FastInstructionList
   37 parameterizedInstructionsParser = many1 parameterizedInstructionParser
   38 
   39 parameterizedInstructionParser ∷ ReadP FastInstruction
   40 parameterizedInstructionParser =
   41       moveRParser <|> moveLParser
   42   <|> incParser   <|> decParser
   43   <|> outParser   <|> inParser
   44   <|> whileParser
   45 
   46 moveRParser ∷ ReadP FastInstruction
   47 moveRParser = Move 1 <$ char '>'
   48 
   49 moveLParser ∷ ReadP FastInstruction
   50 moveLParser = Move negate1 <$ char '<'
   51 
   52 incParser ∷ ReadP FastInstruction
   53 incParser = Inc 1 <$ char '+'
   54 
   55 decParser ∷ ReadP FastInstruction
   56 decParser = Inc negate1 <$ char '-'
   57 
   58 outParser ∷ ReadP FastInstruction
   59 outParser = Output <$ char '.'
   60 
   61 inParser ∷ ReadP FastInstruction
   62 inParser = Input <$ char ','
   63 
   64 whileParser ∷ ReadP FastInstruction
   65 whileParser = While <$> (char '[' *> parameterizedInstructionsParser <* char ']')
   66 
   67 filterComments ∷ Source → Source
   68 filterComments = Text.filter isNotComment
   69 
   70 isNotComment ∷ Char → Bool
   71 isNotComment c = c `elem` allInstructionChars
   72 
   73 allInstructionChars ∷ String
   74 allInstructionChars = "[]" <> simpleInstructionChars
   75 
   76 simpleInstructionChars ∷ String
   77 simpleInstructionChars = show =<< Simple.simpleInstructions
   78 
   79 --
   80 
   81 negate1 ∷ Integer
   82 negate1 = negate 1