src/Misc.hs

   1 -- | The Misc module contains helper functions that seem out of place
   2 --   anywhere else.
   3 module Misc
   4 where
   5
   6
   7 -- | The standard factorial function. See
   8 --   <http://www.willamette.edu/~fruehr/haskell/evolution.html> for
   9 --   possible improvements.
  10 factorial :: Int -> Int
  11 factorial n
  12     | n <= 1 = 1
  13     | n > 20 = error "integer overflow in factorial function"
  14     | otherwise = product [1..n]
  15
  16
  17 -- | Takes a three-dimensional list, and flattens it into a
  18 --   one-dimensional one.
  19 flatten :: [[[a]]] -> [a]
  20 flatten xs = concat $ concat xs
  21
  22
  23 -- | Takes a list, and returns True if its elements are pairwise
  24 --   equal. Returns False otherwise.
  25 all_equal :: (Eq a) => [a] -> Bool
  26 all_equal xs =
  27     and $ map (== first_element) other_elements
  28     where
  29       first_element  = head xs
  30       other_elements = tail xs