Planar direction subtype

src/Swarm/Game/Location.hs

@@ -44,7 +44,7 @@ import Data.Map qualified as M
 import Data.Yaml (FromJSON (parseJSON), ToJSON (toJSON))
 import Linear (Additive (..), V2 (..), negated, norm, perp, unangle)
 import Linear.Affine (Affine (..), Point (..), origin)
-import Swarm.Language.Syntax (AbsoluteDir (..), Direction (..), RelativeDir (..), PlanarRelativeDir (..), isCardinal)
+import Swarm.Language.Syntax (AbsoluteDir (..), Direction (..), PlanarRelativeDir (..), RelativeDir (..), isCardinal)
 import Swarm.Util qualified as Util
 
 -- $setup

src/Swarm/Language/Syntax.hs

@@ -157,6 +157,8 @@ instance FromJSONKey AbsoluteDir where
 data RelativeDir = DPlanar PlanarRelativeDir | DDown
   deriving (Eq, Ord, Show, Read, Generic, Data, Hashable, ToJSON, FromJSON)
 
+-- | Caution: Do not alter this ordering, as there exist functions that depend on it
+-- (e.g. "nearestDirection" and "relativeTo").
 data PlanarRelativeDir = DForward | DLeft | DBack | DRight
   deriving (Eq, Ord, Show, Read, Generic, Data, Hashable, ToJSON, FromJSON, Enum, Bounded)
 
@@ -165,7 +167,7 @@ data PlanarRelativeDir = DForward | DLeft | DBack | DRight
 data Direction = DAbsolute AbsoluteDir | DRelative RelativeDir
   deriving (Eq, Ord, Show, Read, Generic, Data, Hashable, ToJSON, FromJSON)
 
--- | Direction name is generated from Direction data constuctor
+-- | Direction name is generated from Direction data constructor
 -- e.g. DLeft becomes "left"
 directionSyntax :: Direction -> Text
 directionSyntax d = toLower . T.tail . from $ case d of