Make / slightly more efficient

bench/bench.hs

@@ -74,6 +74,15 @@ main = defaultMain
          , benchRead "12345678900000000000.12345678900000000000000000"
          , benchRead "12345678900000000000.12345678900000000000000000e1234"
          ]
+
+       , bgroup "division"
+         [ bench (show n ++ " / " ++ show d) $ nf (uncurry (/)) t
+         | t@(n, d) <-
+           [ (0.4     , 20.0)
+           , (0.4e-100, 0.2e50)
+           ] :: [(Scientific, Scientific)]
+         ]
+
        ]
     where
       pos :: Fractional a => a

changelog

@@ -17,6 +17,8 @@
 	  efficient than using `scientific` because no expensive normalization has to be
 	  performed.
 
+	* Make / on Scientifics slightly more efficient.
+
 0.3.6.2
 	* Due to a regression introduced in 0.3.4.14 the RealFrac methods
 	and floatingOrInteger became vulnerable to a space blowup when

src/Data/Scientific/Internal.hs

@@ -144,7 +144,7 @@ unsafeScientificFromNormalized = Scientific
 -- because no expensive normalization has to be performed.
 unsafeScientificFromNonNormalized
     :: Integer -- ^ coefficient
-    -> Int     -- ^ number of trailing 0s in the coefficient
+    -> Int     -- ^ number of trailing 0s in the coefficient. This should be positive!
     -> Int     -- ^ base-10 exponent
     -> Scientific
 unsafeScientificFromNonNormalized 0 _ _ = Scientific 0 0
@@ -265,15 +265,23 @@ instance Real Scientific where
 -- | /WARNING:/ 'recip' and '/' will throw an error when their outputs are
 -- <https://en.wikipedia.org/wiki/Repeating_decimal repeating decimals>.
 --
+-- These methods also compute 'Integer' magnitudes (@10^e@). If these methods
+-- are applied to arguments which have huge exponents this could fill up all
+-- space and crash your program! So don't apply these methods to scientific
+-- numbers coming from untrusted sources.
+--
 -- 'fromRational' will throw an error when the input 'Rational' is a repeating
 -- decimal.  Consider using 'fromRationalRepetend' for these rationals which
 -- will detect the repetition and indicate where it starts.
 instance Fractional Scientific where
     recip = fromRational . recip . toRational
-    {-# INLINABLE recip #-}
 
-    x / y = fromRational $ toRational x / toRational y
-    {-# INLINABLE (/) #-}
+    Scientific c1 e1 / Scientific c2 e2
+        | d < 0     = fromRational (x / (fromInteger (magnitude (-d))))
+        | otherwise = fromRational (x *  fromInteger (magnitude   d))
+      where
+        d = e1 - e2
+        x = c1 % c2
 
     fromRational rational =
         case mbRepetendIx of