using a modern lib - covered briefly

consoledsl_done.hs

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+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
+import Polysemy
+import Test.Hspec
+
+-- kind must be :: (* -> *) -> * -> *
+data Console m a where
+  PrintLine :: String -> Console m ()
+  ReadLine :: Console m String
+
+makeSem ''Console
+
+-- printLine :: Member Console r => String -> Sem r ()
+-- readLine :: Member Console r => Sem r a
+-- run :: Sem '[] a -> a
+-- runM :: Sem '[Embed m] a -> m a
+-- embed :: Member (Embed m) r => m a -> Sem r a
+
+runConsoleIO :: Member (Embed IO) r => Sem (Console ': r) a -> Sem r a
+runConsoleIO = interpret $ \case
+  PrintLine msg -> embed $ putStrLn msg
+  ReadLine -> embed $ getLine
+
+runConsolePure :: String -> Sem (Console ': r) a -> Sem r a
+runConsolePure s = interpret $ \case
+  PrintLine msg -> pure ()
+  ReadLine -> pure s
+
+spec :: Spec
+spec = describe "program" $ do
+  it "adds 2 numbers given by user" $ do
+    let res = run . runConsolePure "7" $ program
+    res `shouldBe` (7 + 7)
+
+program :: Member Console r => Sem r Int
+program = do
+  printLine "Insert number 1"
+  a <- readLine
+  printLine "Insert number 2"
+  b <- readLine
+  pure $ read a + read b
+
+main :: IO ()
+main = execute >>= print
+  where
+    execute = runM . runConsoleIO $ program