3_a_1: Add solution

2 files changed, 15 insertions, 1 deletions

diff --git a/README.md b/README.md
index 27627ef..ae090f7 100644
--- a/README.md
+++ b/README.md
@@ -51,7 +51,7 @@ more visible in the list the first exercise of a group is in bold italics.
 | **_2_b_1_**    | yes    | 39   | |
 | 2_b_2          | yes    |      | |
 | 2_b_3          | yes    |      | |
-| **_3_a_1_**    |        | 60   | 3. Defining types, streamlining functions |
+| **_3_a_1_**    | yes    | 60   | 3. Defining types, streamlining functions |
 | 3_a_2          |        |      | |
 | **_3_b_1_**    |        | 69   | |
 | 3_b_2          |        |      | |
diff --git a/ch03/3_a_1.hs b/ch03/3_a_1.hs
new file mode 100644
index 0000000..6e2b634
--- /dev/null
+++ b/ch03/3_a_1.hs
@@ -0,0 +1,14 @@
+-- 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]