From fc00cff556372e914d3cf15c39700b4ff7c3541c Mon Sep 17 00:00:00 2001
From: Arnaud Bailly <arnaud@pankzsoft.com>
Date: Sun, 2 Nov 2025 21:35:19 +0100
Subject: better rendering for type errors and evaluation

---
 lambda-calcul/haskell/src/Minilang/REPL/Haskeline.hs | 9 ++-------
 lambda-calcul/haskell/src/Minilang/REPL/Run.hs       | 3 ++-
 2 files changed, 4 insertions(+), 8 deletions(-)

(limited to 'lambda-calcul/haskell/src/Minilang/REPL')

diff --git a/lambda-calcul/haskell/src/Minilang/REPL/Haskeline.hs b/lambda-calcul/haskell/src/Minilang/REPL/Haskeline.hs
index cbc7988..3583020 100644
--- a/lambda-calcul/haskell/src/Minilang/REPL/Haskeline.hs
+++ b/lambda-calcul/haskell/src/Minilang/REPL/Haskeline.hs
@@ -29,6 +29,7 @@ import System.Console.Haskeline
 import System.Directory (listDirectory)
 import Minilang.Lambda.Parser (resugar, pretty)
 import qualified Minilang.Lambda.Unify as Unify
+import Minilang.REPL.Pure (render)
 
 -- * Haskeline REPL
 
@@ -44,19 +45,13 @@ instance MonadREPL Haskeline where
     case i of
       Nothing -> pure EOF
       Just (pack -> t) -> pure $ interpret t
-  output = hoist . outputStrLn . render
+  output = hoist . outputStrLn . unpack . render
   prompt = pure ()
   load = fmap (first FileError) . hoist . lift . try . Text.readFile . unpack
 
   getEnv = get
   setEnv = put
 
-render :: Out -> String
-render = \case
-  Msg t -> unpack t
-  Evaluated term typ -> unpack $ pretty (resugar term) <> " : " <> Unify.pretty typ
-  other -> show other
-
 completion :: CompletionFunc IO
 completion = completion' . first reverse
 
diff --git a/lambda-calcul/haskell/src/Minilang/REPL/Run.hs b/lambda-calcul/haskell/src/Minilang/REPL/Run.hs
index c90ecde..9c31987 100644
--- a/lambda-calcul/haskell/src/Minilang/REPL/Run.hs
+++ b/lambda-calcul/haskell/src/Minilang/REPL/Run.hs
@@ -16,6 +16,7 @@ import Minilang.Lambda.Eval (newEnv)
 import Minilang.Lambda.Infer (infer, newContext)
 import Minilang.Lambda.Parser (desugar, parse)
 import Minilang.REPL.Types
+import qualified Minilang.Lambda.Infer as Infer
 
 -- | Run a REPL session
 runREPL ::
@@ -41,7 +42,7 @@ handleUserInput txt = do
     Right expr -> do
       let term = desugar expr
       case infer term of
-        Left typeError -> output (Msg $ pack $ show typeError)
+        Left typeError -> output (Msg $ Infer.render typeError)
         Right typ -> do
           let v = fromDeBruijn $ eval (toDeBruijn term)
           output (Evaluated v typ)
-- 
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