3_b_6: Add solution

1 files changed, 25 insertions, 0 deletions

diff --git a/ch03/3_b_6.hs b/ch03/3_b_6.hs
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+-- Create a function that sorts a list of lists based on the length of each
+-- sublist. (You may want to look at the sortBy function from the Data.List
+-- module.)
+
+import Data.List
+
+myCompare :: [a] -> [a] -> Ordering
+myCompare a b = if len_a < len_b
+                then LT
+                else if len_a == len_b
+                     then EQ
+                     else GT
+  where len_a = length a
+        len_b = length b
+
+mySort :: [[a]] -> [[a]]
+mySort xs = Data.List.sortBy myCompare xs
+
+-- ghci> :l 3_b_6.hs
+-- [1 of 1] Compiling Main             ( 3_b_6.hs, interpreted )
+-- Ok, one module loaded.
+-- ghci> mySort []
+-- []
+-- ghci> mySort [[2, 3], [7, 8, 9, 10], [1], [], [4, 5, 6]]
+-- [[],[1],[2,3],[4,5,6],[7,8,9,10]]