add Hashable instance for SizeSpec2D

diagrams · Nov 28, 2013 · f7a4aca · f7a4aca
1 parent 615527a
commit f7a4aca
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Showing 2 changed files with 8 additions and 2 deletions.
diff --git a/diagrams-lib.cabal b/diagrams-lib.cabal
@@ -102,6 +102,7 @@ Library
                        tagged >= 0.7,
                        optparse-applicative >= 0.7 && < 0.8,
                        filepath,
-                       safe >= 0.2 && < 0.4
+                       safe >= 0.2 && < 0.4,
+                       hashable >= 1.2 && < 1.3
   Hs-source-dirs:      src
   default-language:    Haskell2010
diff --git a/src/Diagrams/TwoD/Size.hs b/src/Diagrams/TwoD/Size.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE DeriveGeneric    #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE TypeFamilies     #-}
 
@@ -35,6 +36,8 @@ import           Diagrams.TwoD.Vector
 
 import           Control.Applicative  (liftA2, (<$>))
 import           Control.Arrow        ((&&&), (***))
+import           Data.Hashable        (Hashable)
+import           GHC.Generics         (Generic)
 
 ------------------------------------------------------------
 -- Computing diagram sizes
@@ -93,7 +96,9 @@ data SizeSpec2D = Width  !Double       -- ^ Specify an explicit
                 | Absolute            -- ^ Absolute size: use whatever
                                       -- size an object already has;
                                       -- do not rescale.
-  deriving (Eq, Ord, Show)
+  deriving (Eq, Ord, Show, Generic)
+
+instance Hashable SizeSpec2D
 
 -- | Create a size specification from a possibly-specified width and
 --   height.