add builtins.mul, issue #250

data/nix

@@ -1 +1 @@
-Subproject commit 8cc0796bec18057b3feadd1c39ed3f669078a075
+Subproject commit 66707728d0b82754354f0bcd24f32e43500bd86e

src/Nix/Builtins.hs

@@ -164,6 +164,7 @@ builtinsList = sequence [
     , add  Normal   "listToAttrs"                listToAttrs
     , add2 TopLevel "map"                        map_
     , add2 Normal   "match"                      match_
+    , add2 Normal   "mul"                        mul_
     , add  Normal   "parseDrvName"               parseDrvName
     , add2 Normal   "partition"                  partition_
     , add  Normal   "pathExists"                 pathExists_
@@ -282,6 +283,16 @@ add_ x y = x >>= \x' -> y >>= \y' -> case (x', y') of
     (_, _) ->
         throwError $ Addition x' y'
 
+mul_ :: MonadNix e m => m (NValue m) -> m (NValue m) -> m (NValue m)
+mul_ x y = x >>= \x' -> y >>= \y' -> case (x', y') of
+    (NVConstant (NInt x),   NVConstant (NInt y))   ->
+        toNix ( x * y :: 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 $ Multiplication x' y'
+
 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))   ->

src/Nix/Render/Frame.hs

@@ -126,6 +126,7 @@ renderValueFrame level = pure . (:[]) . \case
     Comparison _ _     -> text "Comparing"
     Addition _ _       -> text "Adding"
     Division _ _       -> text "Dividing"
+    Multiplication _ _ -> text "Multiplying"
 
     Coercion x y ->
         text desc <> text (describeValue x)

src/Nix/Value.hs

@@ -318,6 +318,7 @@ data ValueFrame m
     | ConcerningValue (NValue m)
     | Comparison (NValue m) (NValue m)
     | Addition (NValue m) (NValue m)
+    | Multiplication (NValue m) (NValue m)
     | Division (NValue m) (NValue m)
     | Coercion ValueType ValueType
     | CoercionToJsonNF (NValueNF m)