Monoids for File construction

src/Ubc/Parse/Syntax/File.hs

@@ -1,3 +1,5 @@
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE DerivingVia #-}
 module Ubc.Parse.Syntax.File
 ( File(..)
 , parse
@@ -17,36 +19,31 @@ import qualified Ubc.Parse.Syntax.Struct as Struct
 import qualified Ubc.Parse.Syntax.Function as Function
 import qualified Ubc.Parse.Syntax.Statement as Statement
 import qualified Ubc.Parse.Syntax.Enumeration as Enumeration
+import GHC.Generics (Generic)
+import Data.Functor ((<&>))
 
 data File = File
         { name :: String
-        , structs :: [Struct]
+        , body :: FileBody
+        }
+        deriving (Show)
+
+data FileBody = FileBody
+        { structs :: [Struct]
         , functions :: [Function]
         , statements :: [Statement]
         , enumerations :: [Enumeration]
         }
-        deriving (Show)
-
-data FileMember = FileFunction Function
-        | FileStruct Struct
-        | FileEnumeration Enumeration
-        | FileStatement Statement
-
-accumulateFile :: File -> FileMember -> File
-accumulateFile (File name_ sss fs sts es) (FileStruct s)       = File name_ (s:sss) fs        sts     es
-accumulateFile (File name_ sss fs sts es) (FileFunction f)     = File name_    sss  (f:fs)    sts     es
-accumulateFile (File name_ sss fs sts es) (FileStatement s)    = File name_    sss  fs     (s:sts)    es
-accumulateFile (File name_ sss fs sts es) (FileEnumeration e)  = File name_    sss  fs        sts  (e:es)
+        deriving stock (Show, Generic)
+        deriving (Semigroup, Monoid) via FileBody
 
 parse :: Monad m => ParsecT String u m File
-parse = foldr (flip accumulateFile) (File "" [] [] [] []) <$!> many fileMember
+parse = File "" <$!> mconcat <$!> many fileMember
 
-fileMember :: Monad m => ParsecT String u m FileMember
+fileMember :: Monad m => ParsecT String u m FileBody
 fileMember = choice
-                [ FileStruct <$!> Struct.parse
-                , FileFunction <$!> Function.parse
-                , FileStatement <$!> Statement.parse
-                , FileEnumeration <$!> Enumeration.parse
+                [ Struct.parse      <&> \s -> mempty { structs = [s] }
+                , Function.parse    <&> \f -> mempty { functions = [f] }
+                , Statement.parse   <&> \s -> mempty { statements = [s] }
+                , Enumeration.parse <&> \e -> mempty { enumerations = [e] }
                 ]
-
-