3_b_4: Add solution

1 files changed, 15 insertions, 0 deletions

diff --git a/ch03/3_b_4.hs b/ch03/3_b_4.hs
new file mode 100644
index 0000000..a711085
--- /dev/null
+++ b/ch03/3_b_4.hs
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+-- Turn a list into a palindrome, i.e. it should read the same both backwards
+-- and forwards. For example, given the list [1,2,3], your function should
+-- return [1,2,3,3,2,1].
+
+makePalindrome :: [a] -> [a]
+makePalindrome [] = []
+makePalindrome (x:xs) = [x] ++ (makePalindrome xs) ++ [x]
+
+-- ghci> :l 3_b_4.hs
+-- [1 of 1] Compiling Main             ( 3_b_4.hs, interpreted )
+-- Ok, one module loaded.
+-- ghci> makePalindrome []
+-- []
+-- ghci> makePalindrome [1, 2, 3]
+-- [1,2,3,3,2,1]