never executed always true always false

    1 {-# LANGUAGE DataKinds #-}
    2 module Parse.Binop (binops) where
    3 
    4 import Text.Parsec ((<|>), choice, try)
    5 
    6 import AST.V0_16
    7 import AST.Structure (FixAST)
    8 import Data.Coapplicative
    9 import qualified Data.Indexed as I
   10 import Parse.Helpers (commitIf, addLocation, multilineToBool)
   11 import Parse.IParser
   12 import Parse.Whitespace
   13 import Reporting.Annotation (Located)
   14 
   15 
   16 binops
   17     :: IParser (FixAST Located typeRef ctorRef varRef 'ExpressionNK)
   18     -> IParser (FixAST Located typeRef ctorRef varRef 'ExpressionNK)
   19     -> IParser varRef
   20     -> IParser (FixAST Located typeRef ctorRef varRef 'ExpressionNK)
   21 binops term last anyOp =
   22   fmap I.Fix $ addLocation $
   23   do  ((e, ops), multiline) <- trackNewline ((,) <$> term <*> nextOps)
   24       return $
   25         case ops of
   26           [] ->
   27             extract $ I.unFix e
   28           _ ->
   29             Binops e ops $ multilineToBool multiline
   30   where
   31     nextOps =
   32       choice
   33         [ commitIf (whitespace >> anyOp) $
   34             do  preOpComments <- whitespace
   35                 op <- anyOp
   36                 preExpressionComments <- whitespace
   37                 expr <- Left <$> try term <|> Right <$> last
   38                 case expr of
   39                   Left t -> (:) (BinopsClause preOpComments op preExpressionComments t) <$> nextOps
   40                   Right e -> return [BinopsClause preOpComments op preExpressionComments e]
   41         , return []
   42         ]