Wow. Macros?

lib/src/Okapi/NewDSL.hs

@@ -12,15 +12,16 @@ import Data.Kind (Type)
 
 -- type Interpreter (expr :: * -> *) state error a = state -> expr a -> (Either error a, state)
 
-class Evalable (expr :: * -> *) state error where
-    eval :: state -> expr a -> (Either error a, state)
+class Context (expr :: * -> *) state error where
+  eval :: state -> expr a -> (Either error a, state)
 
 data DSL (expr :: * -> *) state error a where
   FMap :: (a -> a') -> DSL expr state error a -> DSL expr state error a'
   Pure :: a -> DSL expr state error a
   Apply :: DSL expr state error (a -> b) -> DSL expr state error a -> DSL expr state error b
 --   Eval :: Interpreter expr state error a -> expr a -> DSL expr state error a
-  Eval :: Evalable expr state error => expr a -> DSL expr state error a
+  Expr :: Context expr state error => expr a -> DSL expr state error a -- Call Quote?
+  -- Add constructor for Combinator??
 
 instance Functor (DSL expr state error) where
   fmap = FMap
@@ -29,7 +30,7 @@ instance Applicative (DSL expr state error) where
   pure = Pure
   (<*>) = Apply
 
-exec :: Evalable expr state error => state -> DSL expr state error a -> (Either error a, state)
+exec :: Context expr state error => state -> DSL expr state error a -> (Either error a, state)
 exec state (FMap f expr) = case exec state expr of
   (Left e, state') -> (Left e, state')
   (Right o, state') -> (Right $ f o, state')
@@ -39,4 +40,7 @@ exec state (Apply progF progX) = case exec state progF of
     (Right x, state'') -> (Right $ f x, state'')
     (Left e, state'') -> (Left e, state'')
   (Left e, state') -> (Left e, state')
-exec state (Eval expr) = eval state expr
+exec state (Expr expr) = eval state expr
+
+-- expr :: Context expr state error => expr a -> DSL expr state error a
+-- expr = Expr

lib/src/Okapi/Parser/Path.hs

@@ -15,6 +15,8 @@ import qualified Web.HttpApiData as Web
 data Expr a where
   Static :: Web.ToHttpApiData a => a -> Expr ()
   Param :: Web.FromHttpApiData a => Expr a
+--   Optional :: Expr a -> Expr (Maybe a)
+  Macro :: Context expr state error => DSL expr state error a -> Expr a
   End :: Expr ()
 
 type State = [Text]
@@ -22,23 +24,28 @@ type State = [Text]
 data Error where
   Error :: Text -> Error
 
-instance Evalable Expr State Error where
+instance Context Expr State Error where
   eval state expr = case expr of
     Static @t x -> undefined
     Param @t -> undefined
+    -- Optional expr' -> undefined
+    Macro dsl -> undefined
     End -> undefined
 
 -- embed :: Expr a -> DSL Expr State Error a
 -- embed = Eval interpreter
 
 static :: Web.ToHttpApiData a => a -> DSL Expr State Error ()
-static = Eval . Static
+static = Expr . Static
 
 param :: Web.FromHttpApiData a => DSL Expr State Error a
-param = Eval Param
+param = Expr Param
+
+-- optional :: Expr a -> DSL Expr State Error (Maybe a)
+-- optional = Expr . Optional
 
 end :: Web.FromHttpApiData a => DSL Expr State Error ()
-end = Eval End
+end = Expr End
 
 -- instance DSL Expr [Text] Error where
 --   eval :: Expr -> [Text] -> (Either Error Result, [Text])