Add two examples (doctests) for the factorial function.

[spline3.git] / src / Misc.hs

diff --git a/src/Misc.hs b/src/Misc.hs
index 6364e95e2c6f3b97794a609bbc7df6c40bd9b65a..48482b4f69a2cfe580b8b34a605beae82565168b 100644 (file)
--- a/src/Misc.hs
+++ b/src/Misc.hs
@@ -7,6 +7,15 @@ where
 -- | The standard factorial function. See
 --   <http://www.willamette.edu/~fruehr/haskell/evolution.html> for
 --   possible improvements.
+--
+--   Examples:
+--
+--   >>> factorial 0
+--   1
+--
+--   >>> factorial 4
+--   24
+--
 factorial :: Int -> Int
 factorial n
     | n <= 1 = 1
@@ -18,3 +27,13 @@ factorial n
 --   one-dimensional one.
 flatten :: [[[a]]] -> [a]
 flatten xs = concat $ concat xs
+
+
+-- | Takes a list, and returns True if its elements are pairwise
+--   equal. Returns False otherwise.
+all_equal :: (Eq a) => [a] -> Bool
+all_equal xs =
+    all (== first_element) other_elements
+    where
+      first_element  = head xs
+      other_elements = tail xs