fromEnumTo consistent with enumFromTo, barring rounding errors.]

bjornbm · Mar 4, 2014 · aadffc6 · aadffc6
1 parent 9a03614
commit aadffc6
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Showing 2 changed files with 17 additions and 5 deletions.
diff --git a/Numeric/Units/Dimensional/DK.hs b/Numeric/Units/Dimensional/DK.hs
@@ -88,7 +88,7 @@ module Numeric.Units.Dimensional.DK
 
 import Prelude
   ( Show, Eq, Ord, Num, Fractional, Floating, RealFloat, Functor, fmap
-  , (.), flip, show, (++), undefined, otherwise, (==), (<=), String, unwords
+  , (.), flip, show, (++), undefined, otherwise, (==), (<=), (>=), String, unwords
   , map, null, Integer, Int, ($), zipWith, uncurry, concat, iterate, takeWhile
   )
 import qualified Prelude
@@ -471,17 +471,21 @@ fromIncr :: (Ord a, Num a)
 fromIncr x0 dx = iterate (+ dx) x0
 
 -- | @fromIncrTo x0 dx xf@ corresponds to @[x0, x0+dx .. xf]@.
-fromIncrTo :: (Ord a, Num a)
+fromIncrTo :: (Ord a, Fractional a)
            => Quantity d a -> Quantity d a -> Quantity d a -> [Quantity d a]
-fromIncrTo x0 dx xf = takeWhile (<= xf) $ fromIncr x0 dx
+--fromIncrTo x0 dx xf = let op = if dx >= _0 then (<=) else (>=)
+--                      in takeWhile (`op` xf) $ fromIncr x0 dx
+fromIncrTo x0 dx xf = if dx >= _0
+                        then takeWhile (<= xf + dx / _2) $ fromIncr x0 dx
+                        else takeWhile (>= xf + dx / _2) $ fromIncr x0 dx
 
 -- | @fromThen x0 dx@ corresponds to @enumFromThen@ or @[x0, x1 ..]@.
 fromThen :: (Ord a, Num a)
          => Quantity d a -> Quantity d a -> [Quantity d a]
 fromThen x0 x1 = fromIncr x0 (x1 - x0)
 
 -- | @fromThenTo x0 x1 xf@ corresponds to @enumFromThenTo@ or @[x0, x1 .. xf]@.
-fromThenTo :: (Ord a, Num a)
+fromThenTo :: (Ord a, Fractional a)
            => Quantity d a -> Quantity d a -> Quantity d a -> [Quantity d a]
 fromThenTo x0 x1 = fromIncrTo x0 (x1 - x0)
 

diff --git a/Numeric/Units/Dimensional/DK/Test.hs b/Numeric/Units/Dimensional/DK/Test.hs
@@ -4,7 +4,9 @@ module Numeric.Units.Dimensional.DK.Test where
 
 import Numeric.Units.Dimensional.DK.Prelude
 import qualified Prelude
+import Data.AEq
 import Test.HUnit
+import Test.QuickCheck
 
 testPower = TestLabel "Power test" $ TestList
     [ TestCase $ (9 *~ one) @=? (3 *~ one) ^ pos2
@@ -31,5 +33,11 @@ tests = TestList
     , testShow
     ]
 
-main = runTestTT tests
+prop_fromEnumTo x0 x1 xf = let
+    xs = enumFromThenTo (x0::Double) x1 xf
+    ys = fromThenTo (x0*~one) (x1*~one) (xf*~one) /~~ one
+  in take 100 xs ~== take 100 ys
 
+main = do 
+  runTestTT tests
+  quickCheck prop_fromEnumTo