Rel8 support.

bucks.cabal

@@ -15,6 +15,11 @@ flag aeson
      default:         False
      manual:          True
 
+flag rel8
+     description:     Enable Rel8 support
+     default:         False
+     manual:          True
+
 common warnings
     ghc-options: -Wall
 
@@ -28,5 +33,9 @@ library
     if flag(aeson)
        other-modules: Data.Money.JSON
        build-depends: aeson >= 2.0 && < 3.0
+    if flag(rel8)
+       other-modules: Data.Money.Rel8
+       build-depends: rel8 >= 1.4,
+                      scientific
     hs-source-dirs:   src
     default-language: Haskell2010

src/Data/Money.hs

@@ -6,3 +6,6 @@ import Data.Money.Internal as Export
 #ifdef flag_AESON
 import Data.Money.JSON as Export ()
 #endif
+#ifdef flag_REL8
+import Data.Money.Rel8 as Export ()
+#endif

src/Data/Money/Rel8.hs

@@ -0,0 +1,17 @@
+{-# LANGUAGE TypeApplications #-}
+{-# OPTIONS_GHC -Wno-orphans #-}
+module Data.Money.Rel8 () where
+
+import Data.Money.Internal
+
+import Data.Scientific
+import Rel8
+
+instance DBType (Money curr) where
+  typeInformation =
+    let sci = typeInformation @Scientific
+    in TypeInformation { encode = encode sci . realToFrac . getAmount
+                       , decode = fmap (Money . realToFrac) (decode sci)
+                       , typeName = "money"
+                       }
+

stack.yaml

@@ -6,3 +6,7 @@ packages:
 flags:
   bucks:
     aeson: true
+    rel8: true
+
+nix:
+  packages: [postgresql]