never executed always true always false

    1 {-# LANGUAGE DeriveGeneric, DeriveDataTypeable, DeriveFunctor, DeriveTraversable, DeriveFoldable #-}
    2 
    3 module Conjure.Language.Expression.Op.CatchUndef where
    4 
    5 import Conjure.Prelude
    6 import Conjure.Language.Expression.Op.Internal.Common
    7 
    8 import qualified Data.Aeson as JSON             -- aeson
    9 import qualified Data.Aeson.KeyMap as KM
   10 
   11 import qualified Data.Vector as V               -- vector
   12 
   13 
   14 -- | Two arguments:
   15 -- 1st: In-Value
   16 -- 2nd: Default
   17 -- Evaluates to: In-Value if it is defined
   18 --               Default if In-Value is undefined
   19 data OpCatchUndef x = OpCatchUndef x x
   20     deriving (Eq, Ord, Show, Data, Functor, Traversable, Foldable, Typeable, Generic)
   21 
   22 instance Serialize x => Serialize (OpCatchUndef x)
   23 instance Hashable  x => Hashable  (OpCatchUndef x)
   24 instance ToJSON    x => ToJSON    (OpCatchUndef x) where toJSON = genericToJSON jsonOptions
   25 instance FromJSON  x => FromJSON  (OpCatchUndef x) where parseJSON = genericParseJSON jsonOptions
   26 
   27 instance (TypeOf x, Pretty x) => TypeOf (OpCatchUndef x) where
   28     typeOf p@(OpCatchUndef x d) = do
   29         tyX <- typeOf x
   30         tyD <- typeOf d
   31         if typesUnify [tyX, tyD]
   32             then return (mostDefined [tyX, tyD])
   33             else raiseTypeError p
   34 
   35 instance SimplifyOp OpCatchUndef x where
   36     simplifyOp _ = na "simplifyOp{OpCatchUndef}"
   37 
   38 instance Pretty x => Pretty (OpCatchUndef x) where
   39     prettyPrec _ (OpCatchUndef a b) = "catchUndef" <> prettyList prParens "," [a, b]
   40 
   41 instance (VarSymBreakingDescription x, ExpressionLike x) => VarSymBreakingDescription (OpCatchUndef x) where
   42     varSymBreakingDescription (OpCatchUndef x y) = JSON.Object $ KM.fromList
   43         [ ("type", JSON.String "OpCatchUndef")
   44         , ("children", JSON.Array $ V.fromList [ varSymBreakingDescription x
   45                                                , varSymBreakingDescription y
   46                                                ])
   47         ]