app/Gyehoek/Sexp.hs

@@ -4,23 +4,41 @@
 module Gyehoek.Sexp
   ( let_
   , nonempty
+  , nonEmptyGrammar
+  , encode
+  , decode
   )
 where
 
 import Data.Text (Text)
-import Language.SexpGrammar as Sexp hiding (List)
+import Language.SexpGrammar as Sexp hiding (List, encode, decode)
+import Language.SexpGrammar qualified as Sexp
 import Language.SexpGrammar.Generic
-import Data.InvertibleGrammar.Base qualified as IG
+import Data.InvertibleGrammar.Base qualified as IGB
+import Data.InvertibleGrammar qualified as IG
 import Data.InvertibleGrammar.Base ((:-)((:-)))
 import Data.List.NonEmpty (NonEmpty ((:|)))
 import Data.List (List)
-import GHC.Generics
+import Data.Text.Encoding
+import GHC.Generics (Generic)
+import Control.Lens
 
 
+encode :: SexpIso a => a -> Either _ Text
+encode = (_Right %~ decodeUtf8 . view strict) . Sexp.encode
+
+decode :: SexpIso a => Text -> Either String a
+decode = Sexp.decode . view lazy . encodeUtf8
+
+nonEmptyGrammar :: Grammar p (NonEmpty x :- t) (List x :- x :- t)
+nonEmptyGrammar = IGB.Iso
+  (\((x:|xs) :- t) -> xs :- x :- t)
+  (\(xs :- x :- t) -> (x:|xs) :- t)
+
 nonempty :: SexpGrammar a -> SexpGrammar (NonEmpty a)
 nonempty a =
   list (el a >>> rest a) >>>
-    pair >>> iso (uncurry (:|)) (\(x :| xs) -> (x, xs))
+    IG.flipped nonEmptyGrammar
 
 let_
   :: (forall t. Grammar Position (Sexp :- t) (a :- t))