Added signed integers

src/Urbit/Deconstructor.elm

@@ -15,6 +15,7 @@ module Urbit.Deconstructor exposing
     , run
     , runBytes
     , sig
+    , signedInt
     , tape
     , tar
     )
@@ -96,6 +97,19 @@ int =
         )
 
 
+signedInt : Deconstructor (Int -> a) a
+signedInt =
+    int
+        |> fmap
+            (\i ->
+                if Bitwise.and 1 i == 1 then
+                    -(Bitwise.shiftRightBy 1 (1 + i))
+
+                else
+                    Bitwise.shiftRightBy 1 i
+            )
+
+
 float32 : Deconstructor (Float -> a) a
 float32 =
     Deconstructor

tests/Test/Urbit.elm

@@ -139,6 +139,15 @@ tests =
                             )
                     )
                 ]
+            , test "[--8 -8]"
+                (\() ->
+                    Expect.equal
+                        (Just ( 8, -8 ))
+                        (D.runBytes
+                            (D.cell D.signedInt D.signedInt |> D.map Tuple.pair)
+                            (Bytes.fromByteValues [ 0xC1, 0x20, 0xE4, 0x01 ])
+                        )
+                )
             ]
         ]