3_a_1: Add solution

1 files changed, 14 insertions, 0 deletions

diff --git a/ch03/3_a_1.hs b/ch03/3_a_1.hs
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+-- Write the converse of fromList for the List type: a function that takes a
+-- List a and generates a [a].
+
+{-- From examples/examples/ch03/ListADT.hs --}
+data List a = Cons a (List a)
+            | Nil
+              deriving (Show)
+{-- End of code from examples --}
+
+toList (Cons x xs) = x:(toList xs)
+toList Nil         = []
+
+-- ghci> toList (Cons 1 (Cons 2 (Cons 3 Nil)))
+-- [1,2,3]