Add abs.

Closes #2.

src/Data/Int53.purs

@@ -19,7 +19,8 @@
 -- | etc., in the usual way, since the ordinary classes for arithmetic are
 -- | implemented. It should feel pretty much like using an ordinary integer.
 -- |
--- | There are also functions for [`even`](#v:even), [`odd`](#v:odd), and [`pow`](#v:pow).
+-- | There are also functions for [`even`](#v:even), [`odd`](#v:odd), [`pow`](#v:pow),
+-- | and [`abs`](#v:abs).
 -- |
 -- | ### Converting an `Int53` to something else
 -- |
@@ -44,7 +45,7 @@ module Data.Int53
     , fromString, toString
     , ceil, floor, round, truncate
     , even, odd
-    , pow
+    , pow, abs
     ) where
 
 
@@ -312,6 +313,15 @@ pow (Int53 base) (Int53 exponent) =
         else Int53 $ Math.pow base exponent
 
 
+-- | Takes the absolute value.
+-- |
+-- |     abs (fromInt 2) == (fromInt 2)
+-- |     abs (fromInt (-2)) == (fromInt 2)
+-- |     abs (fromInt 0) == (fromInt 0)
+abs :: Int53 -> Int53
+abs (Int53 i) = Int53 $ Math.abs i
+
+
 -- | A class which allows a function to accept eitner an `Int` or an `Int53`,
 -- | work with `Int53` internally, and then return whatever type was provided.
 -- |

test/Test/Main.purs

@@ -134,6 +134,11 @@ main = runTest do
         pow (fromInt 0) (fromInt 0) ==> (fromInt 1)
         pow (fromInt 2) (fromInt (-2)) ==> (fromInt 0)
 
+    test "abs" do
+        abs (fromInt 2) ==> (fromInt 2)
+        abs (fromInt (-2)) ==> (fromInt 2)
+        abs (fromInt 0) ==> (fromInt 0)
+
     test "top" do
         ((topInt53 - one) + one) ==> topInt53