Implement custom sorting methods

Unit 1/Lesson 4/AllNames.hs

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+module AllNames where
+
+names :: [([Char], [Char])]
+names = [("Callum", "Kilmartin"),
+         ("Goudham","Suresh"),
+         ("Theo", "Hardman"),
+         ("Luca","Valentini"),
+         ("Cormac", "Muir")]

Unit 1/Lesson 4/customSorting.hs

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+import Data.List (sort, sortBy)
+import AllNames (names)
+
+compareLastNames :: Ord a1 => (a2, a1) -> (a3, a1) -> Ordering
+compareLastNames name1 name2 = if surname1 > surname2
+                               then GT
+                               else if surname1 < surname2
+                                    then LT
+                                    else EQ
+  where surname1 = snd name1
+        surname2 = snd name2
+
+-- Using Guards for boolean expressions
+
+-- compareLastNames :: Ord a1 => (a2, a1) -> (a3, a1) -> Ordering
+-- compareLastNames name1 name2
+--   | surname1 > surname2 = GT
+--   | surname1 < surname2 = LT
+--   | otherwise = EQ
+--   where
+--       surname1 = snd name1
+--       surname2 = snd name2