From 3b304561f7bf04324ade5181ef0075536e5ba199 Mon Sep 17 00:00:00 2001
From: John Wiegley <johnw@newartisans.com>
Date: Sat, 28 Apr 2018 15:01:12 -0700
Subject: [PATCH] Make div dispatch on value types

---
 src/Nix/Builtins.hs     | 12 +++++++++++-
 src/Nix/Render/Frame.hs |  2 ++
 src/Nix/Value.hs        |  1 +
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/Nix/Builtins.hs b/src/Nix/Builtins.hs
index c919da9..1ef615e 100644
--- a/src/Nix/Builtins.hs
+++ b/src/Nix/Builtins.hs
@@ -134,7 +134,7 @@ builtinsList = sequence [
       )
     , add  TopLevel "derivationStrict"           derivationStrict_
     , add  TopLevel "dirOf"                      dirOf
-    , add' Normal   "div"                        (arity2 (div @Integer))
+    , add2 Normal   "div"                        div_
     , add2 Normal   "elem"                       elem_
     , add2 Normal   "elemAt"                     elemAt_
     , add  Normal   "fetchTarball"               fetchTarball
@@ -272,6 +272,16 @@ unsafeGetAttrPos x y = x >>= \x' -> y >>= \y' -> case (x', y') of
 length_ :: forall e m. MonadNix e m => m (NValue m) -> m (NValue m)
 length_ = toValue . (length :: [NThunk m] -> Int) <=< fromValue
 
+div_ :: MonadNix e m => m (NValue m) -> m (NValue m) -> m (NValue m)
+div_ x y = x >>= \x' -> y >>= \y' -> case (x', y') of
+    (NVConstant (NInt x),   NVConstant (NInt y))   ->
+        toNix (floor (fromInteger x / fromInteger y :: Double) :: Integer)
+    (NVConstant (NFloat x), NVConstant (NInt y))   -> toNix (x / fromInteger y)
+    (NVConstant (NInt x),   NVConstant (NFloat y)) -> toNix (fromInteger x / y)
+    (NVConstant (NFloat x), NVConstant (NFloat y)) -> toNix (x / y)
+    (_, _) ->
+        throwError $ Division x' y'
+
 anyM :: Monad m => (a -> m Bool) -> [a] -> m Bool
 anyM _ []       = return False
 anyM p (x:xs)   = do
diff --git a/src/Nix/Render/Frame.hs b/src/Nix/Render/Frame.hs
index c1098ba..396fcce 100644
--- a/src/Nix/Render/Frame.hs
+++ b/src/Nix/Render/Frame.hs
@@ -123,6 +123,8 @@ renderValueFrame :: (MonadReader e m, Has e Options, MonadFile m)
 renderValueFrame level = pure . (:[]) . \case
     ForcingThunk       -> text "ForcingThunk"
     ConcerningValue _v -> text "ConcerningValue"
+    Comparison _ _     -> text "Comparing"
+    Division _ _       -> text "Dividing"
 
     Coercion x y ->
         text desc <> text (describeValue x)
diff --git a/src/Nix/Value.hs b/src/Nix/Value.hs
index a09f229..573fc2d 100644
--- a/src/Nix/Value.hs
+++ b/src/Nix/Value.hs
@@ -317,6 +317,7 @@ data ValueFrame m
     = ForcingThunk
     | ConcerningValue (NValue m)
     | Comparison (NValue m) (NValue m)
+    | Division (NValue m) (NValue m)
     | Coercion ValueType ValueType
     | CoercionToJsonNF (NValueNF m)
     | CoercionFromJson A.Value