Added fromInt

Author: reactormonk

CHANGELOG.md

@@ -7,6 +7,7 @@ Notable changes to this project are documented in this file. The format is based
 Breaking changes:
 
 New features:
+- `fromInt`
 
 Bugfixes:
 

src/Data/Ring/Extra.purs

@@ -0,0 +1,12 @@
+module Data.Ring.Extra where
+
+import Data.Ord ((>=))
+import Data.Ring (class Ring, one, negate)
+import Data.Monoid (power)
+import Data.Monoid.Additive (Additive(..))
+
+fromInt :: forall a. Ring a => Int -> a
+fromInt x =
+  if x >= 0
+    then (\(Additive i) -> i) (power (Additive one) x)
+    else negate (fromInt (negate x))

test/Test/Main.purs

@@ -5,6 +5,7 @@ import Data.HeytingAlgebra (ff, tt, implies)
 import Data.Ord (abs)
 import Test.Data.Generic.Rep (testGenericRep)
 import Test.Utils (AlmostEff, assert)
+import Data.Ring.Extra (fromInt)
 
 main :: AlmostEff
 main = do
@@ -15,6 +16,7 @@ main = do
     testIntDegree
     testRecordInstances
     testGenericRep
+    testFromInt
 
 foreign import testNumberShow :: (Number -> String) -> AlmostEff
 
@@ -151,3 +153,9 @@ testRecordInstances = do
   assert "Record top" $
     (top :: { a :: Boolean }).a
     == top
+
+testFromInt :: AlmostEff
+testFromInt = do
+  assert "Zero" $ fromInt 0 == 0.0
+  assert "Negative" $ fromInt (-1) == (-1.0)
+  assert "Positive" $ fromInt 1 == 1.0