Add tree example

2026-02-19 20:44:04 +00:00 · 2026-02-19 20:44:04 +00:00 · 55a781eeb8
commit 55a781eeb8
parent 06767e17ea
8 changed files with 588 additions and 12 deletions
--- a/exe/GarnetRs/Wrapped.hs
+++ b/exe/GarnetRs/Wrapped.hs
@ -3,10 +3,12 @@
 module GarnetRs.Wrapped (
    T (..),
    Shape (..),
+    BTree (..),
    hello,
    helloStruct,
    helloShape,
    add,
+    sumTree,
 ) where

 import Data.ByteString
@ -32,6 +34,25 @@ convertShape = \case
    Circle r -> Raw.Shape Raw.Circle $ Raw.set_shape_body_circle $ Raw.Circle_Body r
    Rectangle w h -> Raw.Shape Raw.Rectangle $ Raw.set_shape_body_rectangle $ Raw.Rectangle_Body w h

+data BTree a
+    = Leaf a
+    | Fork (BTree a) (BTree a)
+withBTree :: BTree Int64 -> (Raw.BTree -> IO a) -> IO a
+withBTree = flip \f -> \case
+    Leaf v ->
+        f $ Raw.BTree Raw.Leaf $ Raw.set_bTree_body_leaf $ Raw.Leaf_Body v
+    Fork l r ->
+        withBTree l \lRaw ->
+            withBTree r \rRaw ->
+                alloca \lPtr ->
+                    alloca \rPtr -> do
+                        poke lPtr lRaw
+                        poke rPtr rRaw
+                        f
+                            . Raw.BTree Raw.Fork
+                            . Raw.set_bTree_body_fork
+                            $ Raw.Fork_Body (unsafeFromPtr lPtr) (unsafeFromPtr rPtr)
+
 hello :: ByteString -> IO ()
 hello s = useAsCString s $ Raw.hello . unsafeFromPtr

@ -43,3 +64,6 @@ helloShape = Raw.hello_shape . convertShape

 add :: Int64 -> Int64 -> Int64
 add = Raw.add
+
+sumTree :: BTree Int64 -> IO Int64
+sumTree = flip withBTree Raw.sum_tree
--- a/exe/Main.hs
+++ b/exe/Main.hs
@ -10,3 +10,4 @@ main = do
    helloShape $ Circle 3.14
    helloShape $ Rectangle 10.0 5.0
    putStrLn $ "3 + 4 = " <> show (add 3 4)
+    putStrLn . ("Tree sum: " <>) . show =<< sumTree (Fork (Fork (Leaf 1) (Fork (Leaf 2) (Leaf 3))) (Leaf 4))
--- a/generated/GarnetRs.hs
+++ b/generated/GarnetRs.hs
@ -34,6 +34,7 @@ import qualified HsBindgen.Runtime.Internal.HasFFIType
 import qualified HsBindgen.Runtime.Internal.SizedByteArray
 import qualified HsBindgen.Runtime.LibC
 import qualified HsBindgen.Runtime.Marshal
+import qualified HsBindgen.Runtime.PtrConst
 import qualified Text.Read
 import HsBindgen.Runtime.Internal.TypeEquality (TyEq)
 import Prelude ((<*>), (>>), Eq, Int, Ord, Read, Show, pure, showsPrec)
@ -524,3 +525,417 @@ instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType Shape) "body")

  getField =
    HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"body")
+
+{-| __C declaration:__ @enum BTree_Tag@
+
+    __defined at:__ @garnet_rs.h 33:6@
+
+    __exported by:__ @garnet_rs.h@
+-}
+newtype BTree_Tag = BTree_Tag
+  { unwrap :: FC.CUInt
+  }
+  deriving stock (GHC.Generics.Generic)
+  deriving stock (Eq, Ord)
+  deriving newtype (HsBindgen.Runtime.Internal.HasFFIType.HasFFIType)
+
+instance HsBindgen.Runtime.Marshal.StaticSize BTree_Tag where
+
+  staticSizeOf = \_ -> (4 :: Int)
+
+  staticAlignment = \_ -> (4 :: Int)
+
+instance HsBindgen.Runtime.Marshal.ReadRaw BTree_Tag where
+
+  readRaw =
+    \ptr0 ->
+          pure BTree_Tag
+      <*> HsBindgen.Runtime.Marshal.readRawByteOff ptr0 (0 :: Int)
+
+instance HsBindgen.Runtime.Marshal.WriteRaw BTree_Tag where
+
+  writeRaw =
+    \ptr0 ->
+      \s1 ->
+        case s1 of
+          BTree_Tag unwrap2 ->
+            HsBindgen.Runtime.Marshal.writeRawByteOff ptr0 (0 :: Int) unwrap2
+
+deriving via HsBindgen.Runtime.Marshal.EquivStorable BTree_Tag instance F.Storable BTree_Tag
+
+deriving via FC.CUInt instance Data.Primitive.Types.Prim BTree_Tag
+
+instance HsBindgen.Runtime.CEnum.CEnum BTree_Tag where
+
+  type CEnumZ BTree_Tag = FC.CUInt
+
+  toCEnum = BTree_Tag
+
+  fromCEnum = GHC.Records.getField @"unwrap"
+
+  declaredValues =
+    \_ ->
+      HsBindgen.Runtime.CEnum.declaredValuesFromList [ (0, Data.List.NonEmpty.singleton "Leaf")
+                                                     , (1, Data.List.NonEmpty.singleton "Fork")
+                                                     ]
+
+  showsUndeclared =
+    HsBindgen.Runtime.CEnum.showsWrappedUndeclared "BTree_Tag"
+
+  readPrecUndeclared =
+    HsBindgen.Runtime.CEnum.readPrecWrappedUndeclared "BTree_Tag"
+
+  isDeclared = HsBindgen.Runtime.CEnum.seqIsDeclared
+
+  mkDeclared = HsBindgen.Runtime.CEnum.seqMkDeclared
+
+instance HsBindgen.Runtime.CEnum.SequentialCEnum BTree_Tag where
+
+  minDeclaredValue = Leaf
+
+  maxDeclaredValue = Fork
+
+instance Show BTree_Tag where
+
+  showsPrec = HsBindgen.Runtime.CEnum.shows
+
+instance Read BTree_Tag where
+
+  readPrec = HsBindgen.Runtime.CEnum.readPrec
+
+  readList = Text.Read.readListDefault
+
+  readListPrec = Text.Read.readListPrecDefault
+
+instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType BTree_Tag) "unwrap")
+         ) => GHC.Records.HasField "unwrap" (Ptr.Ptr BTree_Tag) (Ptr.Ptr ty) where
+
+  getField =
+    HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"unwrap")
+
+instance HsBindgen.Runtime.HasCField.HasCField BTree_Tag "unwrap" where
+
+  type CFieldType BTree_Tag "unwrap" = FC.CUInt
+
+  offset# = \_ -> \_ -> 0
+
+{-| __C declaration:__ @Leaf@
+
+    __defined at:__ @garnet_rs.h 34:3@
+
+    __exported by:__ @garnet_rs.h@
+-}
+pattern Leaf :: BTree_Tag
+pattern Leaf = BTree_Tag 0
+
+{-| __C declaration:__ @Fork@
+
+    __defined at:__ @garnet_rs.h 35:3@
+
+    __exported by:__ @garnet_rs.h@
+-}
+pattern Fork :: BTree_Tag
+pattern Fork = BTree_Tag 1
+
+{-| __C declaration:__ @struct Leaf_Body@
+
+    __defined at:__ @garnet_rs.h 38:8@
+
+    __exported by:__ @garnet_rs.h@
+-}
+data Leaf_Body = Leaf_Body
+  { value :: HsBindgen.Runtime.LibC.Int64
+    {- ^ __C declaration:__ @value@
+
+         __defined at:__ @garnet_rs.h 39:11@
+
+         __exported by:__ @garnet_rs.h@
+    -}
+  }
+  deriving stock (GHC.Generics.Generic)
+  deriving stock (Eq, Show)
+
+instance HsBindgen.Runtime.Marshal.StaticSize Leaf_Body where
+
+  staticSizeOf = \_ -> (8 :: Int)
+
+  staticAlignment = \_ -> (8 :: Int)
+
+instance HsBindgen.Runtime.Marshal.ReadRaw Leaf_Body where
+
+  readRaw =
+    \ptr0 ->
+          pure Leaf_Body
+      <*> HsBindgen.Runtime.HasCField.readRaw (Data.Proxy.Proxy @"value") ptr0
+
+instance HsBindgen.Runtime.Marshal.WriteRaw Leaf_Body where
+
+  writeRaw =
+    \ptr0 ->
+      \s1 ->
+        case s1 of
+          Leaf_Body value2 ->
+            HsBindgen.Runtime.HasCField.writeRaw (Data.Proxy.Proxy @"value") ptr0 value2
+
+deriving via HsBindgen.Runtime.Marshal.EquivStorable Leaf_Body instance F.Storable Leaf_Body
+
+instance HsBindgen.Runtime.HasCField.HasCField Leaf_Body "value" where
+
+  type CFieldType Leaf_Body "value" =
+    HsBindgen.Runtime.LibC.Int64
+
+  offset# = \_ -> \_ -> 0
+
+instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType Leaf_Body) "value")
+         ) => GHC.Records.HasField "value" (Ptr.Ptr Leaf_Body) (Ptr.Ptr ty) where
+
+  getField =
+    HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"value")
+
+{-| __C declaration:__ @struct Fork_Body@
+
+    __defined at:__ @garnet_rs.h 42:8@
+
+    __exported by:__ @garnet_rs.h@
+-}
+data Fork_Body = Fork_Body
+  { left :: HsBindgen.Runtime.PtrConst.PtrConst BTree
+    {- ^ __C declaration:__ @left@
+
+         __defined at:__ @garnet_rs.h 43:23@
+
+         __exported by:__ @garnet_rs.h@
+    -}
+  , right :: HsBindgen.Runtime.PtrConst.PtrConst BTree
+    {- ^ __C declaration:__ @right@
+
+         __defined at:__ @garnet_rs.h 44:23@
+
+         __exported by:__ @garnet_rs.h@
+    -}
+  }
+  deriving stock (GHC.Generics.Generic)
+  deriving stock (Eq, Show)
+
+instance HsBindgen.Runtime.Marshal.StaticSize Fork_Body where
+
+  staticSizeOf = \_ -> (16 :: Int)
+
+  staticAlignment = \_ -> (8 :: Int)
+
+instance HsBindgen.Runtime.Marshal.ReadRaw Fork_Body where
+
+  readRaw =
+    \ptr0 ->
+          pure Fork_Body
+      <*> HsBindgen.Runtime.HasCField.readRaw (Data.Proxy.Proxy @"left") ptr0
+      <*> HsBindgen.Runtime.HasCField.readRaw (Data.Proxy.Proxy @"right") ptr0
+
+instance HsBindgen.Runtime.Marshal.WriteRaw Fork_Body where
+
+  writeRaw =
+    \ptr0 ->
+      \s1 ->
+        case s1 of
+          Fork_Body left2 right3 ->
+               HsBindgen.Runtime.HasCField.writeRaw (Data.Proxy.Proxy @"left") ptr0 left2
+            >> HsBindgen.Runtime.HasCField.writeRaw (Data.Proxy.Proxy @"right") ptr0 right3
+
+deriving via HsBindgen.Runtime.Marshal.EquivStorable Fork_Body instance F.Storable Fork_Body
+
+instance HsBindgen.Runtime.HasCField.HasCField Fork_Body "left" where
+
+  type CFieldType Fork_Body "left" =
+    HsBindgen.Runtime.PtrConst.PtrConst BTree
+
+  offset# = \_ -> \_ -> 0
+
+instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType Fork_Body) "left")
+         ) => GHC.Records.HasField "left" (Ptr.Ptr Fork_Body) (Ptr.Ptr ty) where
+
+  getField =
+    HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"left")
+
+instance HsBindgen.Runtime.HasCField.HasCField Fork_Body "right" where
+
+  type CFieldType Fork_Body "right" =
+    HsBindgen.Runtime.PtrConst.PtrConst BTree
+
+  offset# = \_ -> \_ -> 8
+
+instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType Fork_Body) "right")
+         ) => GHC.Records.HasField "right" (Ptr.Ptr Fork_Body) (Ptr.Ptr ty) where
+
+  getField =
+    HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"right")
+
+{-| __C declaration:__ @union \@BTree_body@
+
+    __defined at:__ @garnet_rs.h 49:3@
+
+    __exported by:__ @garnet_rs.h@
+-}
+newtype BTree_body = BTree_body
+  { unwrap :: Data.Array.Byte.ByteArray
+  }
+  deriving stock (GHC.Generics.Generic)
+
+deriving via (HsBindgen.Runtime.Internal.SizedByteArray.SizedByteArray 16) 8 instance HsBindgen.Runtime.Marshal.StaticSize BTree_body
+
+deriving via (HsBindgen.Runtime.Internal.SizedByteArray.SizedByteArray 16) 8 instance HsBindgen.Runtime.Marshal.ReadRaw BTree_body
+
+deriving via (HsBindgen.Runtime.Internal.SizedByteArray.SizedByteArray 16) 8 instance HsBindgen.Runtime.Marshal.WriteRaw BTree_body
+
+deriving via HsBindgen.Runtime.Marshal.EquivStorable BTree_body instance F.Storable BTree_body
+
+{-|
+
+  __See:__ 'set_bTree_body_leaf'
+
+__C declaration:__ @leaf@
+
+__defined at:__ @garnet_rs.h 50:22@
+
+__exported by:__ @garnet_rs.h@
+-}
+get_bTree_body_leaf ::
+     BTree_body
+  -> Leaf_Body
+get_bTree_body_leaf =
+  HsBindgen.Runtime.Internal.ByteArray.getUnionPayload
+
+{-|
+
+  __See:__ 'get_bTree_body_leaf'
+
+-}
+set_bTree_body_leaf ::
+     Leaf_Body
+  -> BTree_body
+set_bTree_body_leaf =
+  HsBindgen.Runtime.Internal.ByteArray.setUnionPayload
+
+{-|
+
+  __See:__ 'set_bTree_body_fork'
+
+__C declaration:__ @fork@
+
+__defined at:__ @garnet_rs.h 51:22@
+
+__exported by:__ @garnet_rs.h@
+-}
+get_bTree_body_fork ::
+     BTree_body
+  -> Fork_Body
+get_bTree_body_fork =
+  HsBindgen.Runtime.Internal.ByteArray.getUnionPayload
+
+{-|
+
+  __See:__ 'get_bTree_body_fork'
+
+-}
+set_bTree_body_fork ::
+     Fork_Body
+  -> BTree_body
+set_bTree_body_fork =
+  HsBindgen.Runtime.Internal.ByteArray.setUnionPayload
+
+instance HsBindgen.Runtime.HasCField.HasCField BTree_body "leaf" where
+
+  type CFieldType BTree_body "leaf" = Leaf_Body
+
+  offset# = \_ -> \_ -> 0
+
+instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType BTree_body) "leaf")
+         ) => GHC.Records.HasField "leaf" (Ptr.Ptr BTree_body) (Ptr.Ptr ty) where
+
+  getField =
+    HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"leaf")
+
+instance HsBindgen.Runtime.HasCField.HasCField BTree_body "fork" where
+
+  type CFieldType BTree_body "fork" = Fork_Body
+
+  offset# = \_ -> \_ -> 0
+
+instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType BTree_body) "fork")
+         ) => GHC.Records.HasField "fork" (Ptr.Ptr BTree_body) (Ptr.Ptr ty) where
+
+  getField =
+    HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"fork")
+
+{-| __C declaration:__ @struct BTree@
+
+    __defined at:__ @garnet_rs.h 47:8@
+
+    __exported by:__ @garnet_rs.h@
+-}
+data BTree = BTree
+  { tag :: BTree_Tag
+    {- ^ __C declaration:__ @tag@
+
+         __defined at:__ @garnet_rs.h 48:18@
+
+         __exported by:__ @garnet_rs.h@
+    -}
+  , body :: BTree_body
+    {- ^ __C declaration:__ @body@
+
+         __defined at:__ @garnet_rs.h 52:5@
+
+         __exported by:__ @garnet_rs.h@
+    -}
+  }
+  deriving stock (GHC.Generics.Generic)
+
+instance HsBindgen.Runtime.Marshal.StaticSize BTree where
+
+  staticSizeOf = \_ -> (24 :: Int)
+
+  staticAlignment = \_ -> (8 :: Int)
+
+instance HsBindgen.Runtime.Marshal.ReadRaw BTree where
+
+  readRaw =
+    \ptr0 ->
+          pure BTree
+      <*> HsBindgen.Runtime.HasCField.readRaw (Data.Proxy.Proxy @"tag") ptr0
+      <*> HsBindgen.Runtime.HasCField.readRaw (Data.Proxy.Proxy @"body") ptr0
+
+instance HsBindgen.Runtime.Marshal.WriteRaw BTree where
+
+  writeRaw =
+    \ptr0 ->
+      \s1 ->
+        case s1 of
+          BTree tag2 body3 ->
+               HsBindgen.Runtime.HasCField.writeRaw (Data.Proxy.Proxy @"tag") ptr0 tag2
+            >> HsBindgen.Runtime.HasCField.writeRaw (Data.Proxy.Proxy @"body") ptr0 body3
+
+deriving via HsBindgen.Runtime.Marshal.EquivStorable BTree instance F.Storable BTree
+
+instance HsBindgen.Runtime.HasCField.HasCField BTree "tag" where
+
+  type CFieldType BTree "tag" = BTree_Tag
+
+  offset# = \_ -> \_ -> 0
+
+instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType BTree) "tag")
+         ) => GHC.Records.HasField "tag" (Ptr.Ptr BTree) (Ptr.Ptr ty) where
+
+  getField =
+    HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"tag")
+
+instance HsBindgen.Runtime.HasCField.HasCField BTree "body" where
+
+  type CFieldType BTree "body" = BTree_body
+
+  offset# = \_ -> \_ -> 8
+
+instance ( TyEq ty ((HsBindgen.Runtime.HasCField.CFieldType BTree) "body")
+         ) => GHC.Records.HasField "body" (Ptr.Ptr BTree) (Ptr.Ptr ty) where
+
+  getField =
+    HsBindgen.Runtime.HasCField.fromPtr (Data.Proxy.Proxy @"body")
--- a/generated/GarnetRs/FunPtr.hs
+++ b/generated/GarnetRs/FunPtr.hs
@ -51,6 +51,14 @@ $(HsBindgen.Runtime.Internal.CAPI.addCSource (HsBindgen.Runtime.Internal.CAPI.un
  , "{"
  , "  return &add;"
  , "}"
+  , "/* com_garnet_GarnetRs_get_sum_tree */"
+  , "__attribute__ ((const))"
+  , "int64_t (*hs_bindgen_473a3e791275b06d (void)) ("
+  , "  struct BTree arg1"
+  , ")"
+  , "{"
+  , "  return &sum_tree;"
+  , "}"
  ]))

 -- __unique:__ @com_garnet_GarnetRs_get_hello@
@ -65,7 +73,7 @@ hs_bindgen_faf62265b53521d3 =
 {-# NOINLINE hello #-}
 {-| __C declaration:__ @hello@

-    __defined at:__ @garnet_rs.h 33:6@
+    __defined at:__ @garnet_rs.h 55:6@

    __exported by:__ @garnet_rs.h@
 -}
@ -85,7 +93,7 @@ hs_bindgen_0f8c37ef19b17a6d =
 {-# NOINLINE hello_struct #-}
 {-| __C declaration:__ @hello_struct@

-    __defined at:__ @garnet_rs.h 35:6@
+    __defined at:__ @garnet_rs.h 57:6@

    __exported by:__ @garnet_rs.h@
 -}
@ -105,7 +113,7 @@ hs_bindgen_287ff3ac660f333b =
 {-# NOINLINE hello_shape #-}
 {-| __C declaration:__ @hello_shape@

-    __defined at:__ @garnet_rs.h 37:6@
+    __defined at:__ @garnet_rs.h 59:6@

    __exported by:__ @garnet_rs.h@
 -}
@ -125,10 +133,30 @@ hs_bindgen_bbabdbe61cd1eeb2 =
 {-# NOINLINE add #-}
 {-| __C declaration:__ @add@

-    __defined at:__ @garnet_rs.h 39:32@
+    __defined at:__ @garnet_rs.h 61:32@

    __exported by:__ @garnet_rs.h@
 -}
 add :: Ptr.FunPtr (HsBindgen.Runtime.LibC.Int64 -> HsBindgen.Runtime.LibC.Int64 -> IO HsBindgen.Runtime.LibC.Int64)
 add =
  GHC.IO.Unsafe.unsafePerformIO hs_bindgen_bbabdbe61cd1eeb2
+
+-- __unique:__ @com_garnet_GarnetRs_get_sum_tree@
+foreign import ccall unsafe "hs_bindgen_473a3e791275b06d" hs_bindgen_473a3e791275b06d_base ::
+     IO (Ptr.FunPtr Void)
+
+-- __unique:__ @com_garnet_GarnetRs_get_sum_tree@
+hs_bindgen_473a3e791275b06d :: IO (Ptr.FunPtr (BTree -> IO HsBindgen.Runtime.LibC.Int64))
+hs_bindgen_473a3e791275b06d =
+  HsBindgen.Runtime.Internal.HasFFIType.fromFFIType hs_bindgen_473a3e791275b06d_base
+
+{-# NOINLINE sum_tree #-}
+{-| __C declaration:__ @sum_tree@
+
+    __defined at:__ @garnet_rs.h 63:9@
+
+    __exported by:__ @garnet_rs.h@
+-}
+sum_tree :: Ptr.FunPtr (BTree -> IO HsBindgen.Runtime.LibC.Int64)
+sum_tree =
+  GHC.IO.Unsafe.unsafePerformIO hs_bindgen_473a3e791275b06d
--- a/generated/GarnetRs/Safe.hs
+++ b/generated/GarnetRs/Safe.hs
@ -44,6 +44,12 @@ $(HsBindgen.Runtime.Internal.CAPI.addCSource (HsBindgen.Runtime.Internal.CAPI.un
  , "{"
  , "  return add(arg1, arg2);"
  , "}"
+  , "int64_t hs_bindgen_9602640c06f0c62f ("
+  , "  struct BTree *arg1"
+  , ")"
+  , "{"
+  , "  return sum_tree(*arg1);"
+  , "}"
  ]))

 -- __unique:__ @com_garnet_GarnetRs_Safe_hello@
@ -60,7 +66,7 @@ hs_bindgen_433ea2a26af4e593 =

 {-| __C declaration:__ @hello@

-    __defined at:__ @garnet_rs.h 33:6@
+    __defined at:__ @garnet_rs.h 55:6@

    __exported by:__ @garnet_rs.h@
 -}
@ -84,7 +90,7 @@ hs_bindgen_51157946af5519c9 =

 {-| __C declaration:__ @hello_struct@

-    __defined at:__ @garnet_rs.h 35:6@
+    __defined at:__ @garnet_rs.h 57:6@

    __exported by:__ @garnet_rs.h@
 -}
@ -110,7 +116,7 @@ hs_bindgen_7de06f1fd827ca60 =

 {-| __C declaration:__ @hello_shape@

-    __defined at:__ @garnet_rs.h 37:6@
+    __defined at:__ @garnet_rs.h 59:6@

    __exported by:__ @garnet_rs.h@
 -}
@ -142,7 +148,7 @@ hs_bindgen_1c0c71fa74c428a9 =

 __C declaration:__ @add@

-__defined at:__ @garnet_rs.h 39:32@
+__defined at:__ @garnet_rs.h 61:32@

 __exported by:__ @garnet_rs.h@
 -}
@ -153,3 +159,29 @@ add ::
     -- ^ __C declaration:__ @b@
  -> HsBindgen.Runtime.LibC.Int64
 add = hs_bindgen_1c0c71fa74c428a9
+
+-- __unique:__ @com_garnet_GarnetRs_Safe_sum_tree@
+foreign import ccall safe "hs_bindgen_9602640c06f0c62f" hs_bindgen_9602640c06f0c62f_base ::
+     Ptr.Ptr Void
+  -> IO GHC.Int.Int64
+
+-- __unique:__ @com_garnet_GarnetRs_Safe_sum_tree@
+hs_bindgen_9602640c06f0c62f ::
+     Ptr.Ptr BTree
+  -> IO HsBindgen.Runtime.LibC.Int64
+hs_bindgen_9602640c06f0c62f =
+  HsBindgen.Runtime.Internal.HasFFIType.fromFFIType hs_bindgen_9602640c06f0c62f_base
+
+{-| __C declaration:__ @sum_tree@
+
+    __defined at:__ @garnet_rs.h 63:9@
+
+    __exported by:__ @garnet_rs.h@
+-}
+sum_tree ::
+     BTree
+     -- ^ __C declaration:__ @t@
+  -> IO HsBindgen.Runtime.LibC.Int64
+sum_tree =
+  \t0 ->
+    F.with t0 (\t1 -> hs_bindgen_9602640c06f0c62f t1)
--- a/generated/GarnetRs/Unsafe.hs
+++ b/generated/GarnetRs/Unsafe.hs
@ -44,6 +44,12 @@ $(HsBindgen.Runtime.Internal.CAPI.addCSource (HsBindgen.Runtime.Internal.CAPI.un
  , "{"
  , "  return add(arg1, arg2);"
  , "}"
+  , "int64_t hs_bindgen_c2ced4f3ba39c8ff ("
+  , "  struct BTree *arg1"
+  , ")"
+  , "{"
+  , "  return sum_tree(*arg1);"
+  , "}"
  ]))

 -- __unique:__ @com_garnet_GarnetRs_Unsafe_hello@
@ -60,7 +66,7 @@ hs_bindgen_2dfe97662a4d6377 =

 {-| __C declaration:__ @hello@

-    __defined at:__ @garnet_rs.h 33:6@
+    __defined at:__ @garnet_rs.h 55:6@

    __exported by:__ @garnet_rs.h@
 -}
@ -84,7 +90,7 @@ hs_bindgen_29d823ada2bc7302 =

 {-| __C declaration:__ @hello_struct@

-    __defined at:__ @garnet_rs.h 35:6@
+    __defined at:__ @garnet_rs.h 57:6@

    __exported by:__ @garnet_rs.h@
 -}
@ -110,7 +116,7 @@ hs_bindgen_b3f40a03f07eaa85 =

 {-| __C declaration:__ @hello_shape@

-    __defined at:__ @garnet_rs.h 37:6@
+    __defined at:__ @garnet_rs.h 59:6@

    __exported by:__ @garnet_rs.h@
 -}
@ -142,7 +148,7 @@ hs_bindgen_20eb651f0a8faf48 =

 __C declaration:__ @add@

-__defined at:__ @garnet_rs.h 39:32@
+__defined at:__ @garnet_rs.h 61:32@

 __exported by:__ @garnet_rs.h@
 -}
@ -153,3 +159,29 @@ add ::
     -- ^ __C declaration:__ @b@
  -> HsBindgen.Runtime.LibC.Int64
 add = hs_bindgen_20eb651f0a8faf48
+
+-- __unique:__ @com_garnet_GarnetRs_Unsafe_sum_tree@
+foreign import ccall unsafe "hs_bindgen_c2ced4f3ba39c8ff" hs_bindgen_c2ced4f3ba39c8ff_base ::
+     Ptr.Ptr Void
+  -> IO GHC.Int.Int64
+
+-- __unique:__ @com_garnet_GarnetRs_Unsafe_sum_tree@
+hs_bindgen_c2ced4f3ba39c8ff ::
+     Ptr.Ptr BTree
+  -> IO HsBindgen.Runtime.LibC.Int64
+hs_bindgen_c2ced4f3ba39c8ff =
+  HsBindgen.Runtime.Internal.HasFFIType.fromFFIType hs_bindgen_c2ced4f3ba39c8ff_base
+
+{-| __C declaration:__ @sum_tree@
+
+    __defined at:__ @garnet_rs.h 63:9@
+
+    __exported by:__ @garnet_rs.h@
+-}
+sum_tree ::
+     BTree
+     -- ^ __C declaration:__ @t@
+  -> IO HsBindgen.Runtime.LibC.Int64
+sum_tree =
+  \t0 ->
+    F.with t0 (\t1 -> hs_bindgen_c2ced4f3ba39c8ff t1)
--- a/rust/garnet_rs.h
+++ b/rust/garnet_rs.h
@ -30,6 +30,28 @@ struct Shape {
  } body;
 };

+enum BTree_Tag {
+  Leaf,
+  Fork,
+};
+
+struct Leaf_Body {
+  int64_t value;
+};
+
+struct Fork_Body {
+  const struct BTree *left;
+  const struct BTree *right;
+};
+
+struct BTree {
+  enum BTree_Tag tag;
+  union {
+    struct Leaf_Body leaf;
+    struct Fork_Body fork;
+  } body;
+};
+
 void hello(const char *c);

 void hello_struct(struct T t);
@ -37,3 +59,5 @@ void hello_struct(struct T t);
 void hello_shape(struct Shape s);

 __attribute__((const)) int64_t add(int64_t a, int64_t b);
+
+int64_t sum_tree(struct BTree t);
--- a/rust/lib.rs
+++ b/rust/lib.rs
@ -40,3 +40,23 @@ extern "C" fn hello_shape(s: Shape) -> () {
 extern "C" fn add(a: i64, b: i64) -> i64 {
    a + b
 }
+
+#[repr(C)]
+#[derive(Clone, Copy)]
+enum BTree {
+    Leaf {
+        value: i64,
+    },
+    Fork {
+        left: *const BTree,
+        right: *const BTree,
+    },
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn sum_tree(t: BTree) -> i64 {
+    match t {
+        BTree::Leaf { value } => value,
+        BTree::Fork { left, right } => unsafe { sum_tree(*left) + sum_tree(*right) },
+    }
+}