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-- Define a function that joins a list of lists together using a separator value.
--
-- -- file: ch03/Intersperse.hs
-- intersperse :: a -> [[a]] -> [a]
--
-- The separator should appear between elements of the list, but should not
-- follow the last element. Your function should behave as follows.
--
-- ghci> :load Intersperse
-- [1 of 1] Compiling Main ( Intersperse.hs, interpreted )
-- Ok, modules loaded: Main.
-- ghci> intersperse ',' []
-- ""
-- ghci> intersperse ',' ["foo"]
-- "foo"
-- ghci> intersperse ',' ["foo","bar","baz","quux"]
-- "foo,bar,baz,quux"
myIntersperse :: a -> [[a]] -> [a]
myIntersperse _ [] = []
myIntersperse _ (x:[]) = x
myIntersperse s (x:xs) = x ++ s:(myIntersperse s xs)
-- ghci> :l 3_b_7.hs
-- [1 of 1] Compiling Main ( 3_b_7.hs, interpreted )
-- Ok, one module loaded.
-- ghci> myIntersperse ',' []
-- ""
-- ghci> myIntersperse ',' ["foo"]
-- "foo"
-- ghci> myIntersperse ',' ["foo","bar","baz","quux"]
-- "foo,bar,baz,quux"
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