1 files changed, 11 insertions, 0 deletions
diff --git a/gcd.hs b/gcd.hs
new file mode 100644
index 0000000..764e824
--- /dev/null
+++ b/gcd.hs
@@ -0,0 +1,11 @@
+import Control.Monad.Writer
+
+gcd' :: Int -> Int -> Writer [String] Int
+gcd' a b
+    | b == 0 = do
+        tell ["Finished with " ++ show a]
+        return a
+    | otherwise = do
+        tell [show a ++ " mod " ++ show b ++ " = " ++ show (a `mod` b)]
+        gcd' b (a `mod` b)
+