From 8a3ca8823d4e8b8adbf3060ec056aafaf9813ded Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Sun, 16 Apr 2017 22:40:46 -0400
Subject: [PATCH] Add an Ord instance for Cidr and use it to implement Eq.

---
 src/Cidr.hs        | 17 ++++++++++++++---
 src/IPv4Address.hs |  2 +-
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/Cidr.hs b/src/Cidr.hs
index d071586..e353406 100644
--- a/src/Cidr.hs
+++ b/src/Cidr.hs
@@ -61,12 +61,14 @@ instance Eq Cidr where
   -- | Two CIDRs are equal if they have the same network bits and if
   --   their masks are the same. In other words, if they are the same
   --   after normalization.
-  cidr1 == cidr2 = addr1 == addr2 && mask1 == mask2
+  cidr1 == cidr2 = (cidr1 <= cidr2) && (cidr2 <= cidr1)
+
+instance Ord Cidr where
+  cidr1 <= cidr2 = if addr1 == addr2 then mask1 <= mask2 else addr1 <= addr2
     where
       Cidr addr1 mask1 = normalize cidr1
       Cidr addr2 mask2 = normalize cidr2
 
-
 -- | Returns the mask portion of a CIDR address. That is, everything
 --   after the trailing slash.
 maskbits_from_cidr_string :: String -> Maybe Maskbits
@@ -300,7 +302,8 @@ cidr_properties =
   testGroup "CIDR Properties" [
       prop_all_cidrs_contain_themselves,
       prop_contains_proper_antisymmetric,
-      prop_normalize_idempotent ]
+      prop_normalize_idempotent,
+      prop_normalize_preserves_equality ]
 
 
 -- HUnit Tests
@@ -549,3 +552,11 @@ prop_normalize_idempotent =
   where
     prop :: Cidr -> Bool
     prop cidr = (normalize cidr) == (normalize (normalize cidr))
+
+-- Normalization should not affect equality of two CIDRs.
+prop_normalize_preserves_equality :: TestTree
+prop_normalize_preserves_equality =
+  testProperty "The CIDR \"normalize\" function preserves equality " prop
+  where
+    prop :: Cidr -> Cidr -> Bool
+    prop cidr1 cidr2 = (cidr1 == cidr2) == (normalize cidr1 == normalize cidr2)
diff --git a/src/IPv4Address.hs b/src/IPv4Address.hs
index 6985944..80a499e 100644
--- a/src/IPv4Address.hs
+++ b/src/IPv4Address.hs
@@ -30,7 +30,7 @@ data IPv4Address =
                 octet2 :: Octet,
                 octet3 :: Octet,
                 octet4 :: Octet }
-    deriving (Eq)
+    deriving (Eq, Ord)
 
 
 instance Show IPv4Address where
-- 
2.43.2