add AffineSpace instance for TimeStamp

JohnLato · Feb 16, 2013 · 7508cef · 7508cef
1 parent 948a24c
commit 7508cef
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diff --git a/Data/ZoomCache/Common.hs b/Data/ZoomCache/Common.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE ExistentialQuantification #-}
+{-# LANGUAGE TypeFamilies #-}
 {-# OPTIONS -Wall #-}
 ----------------------------------------------------------------------
 -- |
@@ -39,6 +40,7 @@ module Data.ZoomCache.Common (
     , Version(..)
 ) where
 
+import Data.AffineSpace
 import Data.Int
 import Data.Ratio
 import Data.Time.Clock (UTCTime, addUTCTime, diffUTCTime)
@@ -78,6 +80,11 @@ newtype TimeStamp = TS Double
 
 newtype TimeStampDiff = TSDiff Double
 
+instance AffineSpace TimeStamp where
+    type Diff TimeStamp = Double
+    TS l .-. TS r = l .-. r
+    TS t .+^ d = TS (t .+^ d)
+
 -- | @timeStampDiff (TS t1) (TS t2) = TSDiff (t1 - t2)@
 timeStampDiff :: TimeStamp -> TimeStamp -> TimeStampDiff
 timeStampDiff (TS t1) (TS t2) = TSDiff (t1 - t2)

diff --git a/zoom-cache.cabal b/zoom-cache.cabal
@@ -93,6 +93,7 @@ Library
     transformers              >= 0.2     && < 0.4,
     type-level,
     unix,
+    vector-space,
     zlib
 
   Exposed-modules:
@@ -154,6 +155,7 @@ Executable zoom-cache
     type-level,
     ui-command,
     unix,
+    vector-space,
     zlib
 
 Test-suite tests
@@ -171,6 +173,7 @@ Test-suite tests
     transformers               >= 0.2     && < 0.4,
     type-level,
     unix,
+    vector-space,
     zoom-cache
 
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