Merge pull request #33 from garyb/approxnum

Add ApproxNumber

Author: garyb

src/Test/StrongCheck/Data/ApproxNumber.purs

@@ -0,0 +1,47 @@
+module Test.StrongCheck.Data.ApproxNumber where
+
+import Prelude
+
+import Test.StrongCheck.Arbitrary (class Coarbitrary, class Arbitrary, coarbitrary, arbitrary)
+
+-- | A newtype for `Number` whose `Eq` instance uses an epsilon value to allow
+-- | for precision erros when comparing.
+newtype ApproxNumber = ApproxNumber Number
+
+-- Approximate equality comparison
+approximateEqual :: Number -> Number -> Boolean
+approximateEqual x y = (y - x) <= epsilon && (y - x) >= (-epsilon)
+  where
+  epsilon = 0.00000001
+
+infix 2 approximateEqual as =~=
+
+instance arbitraryApproxNumber :: Arbitrary ApproxNumber where
+  arbitrary = ApproxNumber <$> arbitrary
+
+instance coarbitraryApproxNumber :: Coarbitrary ApproxNumber where
+  coarbitrary (ApproxNumber n) = coarbitrary n
+
+instance eqApproxNumber :: Eq ApproxNumber where
+  eq (ApproxNumber x) (ApproxNumber y) = x =~= y
+
+instance ordApproxNumber :: Ord ApproxNumber where
+  compare (ApproxNumber x) (ApproxNumber y) = compare x y
+
+instance semiringApproxNumber :: Semiring ApproxNumber where
+  add (ApproxNumber x) (ApproxNumber y) = ApproxNumber (x + y)
+  zero = ApproxNumber zero
+  mul (ApproxNumber x) (ApproxNumber y) = ApproxNumber (x * y)
+  one = ApproxNumber one
+
+instance ringApproxNumber :: Ring ApproxNumber where
+  sub (ApproxNumber x) (ApproxNumber y) = ApproxNumber (x - y)
+
+instance commutativeRingApproxNumber :: CommutativeRing ApproxNumber
+
+instance euclideanRingApproxNumber :: EuclideanRing ApproxNumber where
+  degree (ApproxNumber x) = degree x
+  div (ApproxNumber x) (ApproxNumber y) = ApproxNumber (x / y)
+  mod (ApproxNumber x) (ApproxNumber y) = ApproxNumber (x `mod` y)
+
+instance fieldApproxNumber :: Field ApproxNumber