never executed always true always false

    1 module Parse.State where
    2 
    3 
    4 data State = State
    5   { newline :: [Bool]
    6   }
    7 
    8 
    9 init :: State
   10 init =
   11   State
   12     { newline = [False]
   13     }
   14 
   15 
   16 setNewline :: State -> State
   17 setNewline state =
   18     case newline state of
   19         [] -> state
   20         (_:rest) -> state { newline = (True:rest) }
   21 
   22 
   23 pushNewlineContext :: State -> State
   24 pushNewlineContext state =
   25     state { newline = (False:(newline state)) }
   26 
   27 
   28 popNewlineContext :: State -> State
   29 popNewlineContext state =
   30     case newline state of
   31         [] -> state
   32         (_:[]) -> state
   33         (last:next:rest) -> state { newline = (last || next):rest }
   34 
   35 
   36 sawNewline :: State -> Bool
   37 sawNewline state =
   38     case newline state of
   39         [] -> False
   40         (b:_) -> b