Price: decompose

src/ATrade/Price.hs

@@ -3,7 +3,8 @@
 module ATrade.Price (
   Price(..),
   fromDouble,
-  toDouble
+  toDouble,
+  decompose
 ) where
 
 import Data.Int
@@ -35,3 +36,7 @@ toDouble p = fromIntegral (priceQuants p) / fromIntegral giga
 
 fromDouble :: Double -> Price
 fromDouble d = Price { priceQuants = truncate (d * fromIntegral giga) }
+
+decompose :: Price -> (Int64, Int32)
+decompose Price{priceQuants = p} = (p `div` giga, (fromInteger . toInteger) $ p `mod` giga)
+

test/TestTypes.hs

@@ -35,6 +35,7 @@ properties = testGroup "Types" [
   , testTradeSerialization
   , testPrice1
   , testPrice2
+  , testPriceDecompose
   ]
 
 testTickSerialization = QC.testProperty "Deserialize serialized tick"
@@ -92,3 +93,7 @@ testPrice2 = QC.testProperty "toDouble . fromDouble $ Price" $
   QC.forAll (arbitrary `suchThat` (< 1000000000)) (\d -> let newd = (P.toDouble . P.fromDouble) d in
     (abs (newd - d) < 0.000001))
 
+testPriceDecompose = QC.testProperty "Price decompose"
+  (\p -> let (i, f) = decompose p in
+    i * 1000000000 + (fromInteger . fromIntegral) f == priceQuants p)
+