implement pd

2 files changed, 27 insertions, 1 deletions

diff --git a/AufgabeFFP1.hs b/AufgabeFFP1.hs
index eb9d1fc..8dd52e1 100644
--- a/AufgabeFFP1.hs
+++ b/AufgabeFFP1.hs
@@ -1,5 +1,21 @@
 module AufgabeFFP1
 where
 
+-- calculates 2^ with each element of the continuous list
 pof2s :: [Integer]
 pof2s = map (2^) [0,1..]
+
+-- alternate:
+-- pof2s :: [Integer]
+-- pof2s = iterate (2*) 1
+
+-------------------------------------------------------------------------------
+
+-- iterate steps:
+-- (1) [1]
+-- (2) zipWith (+) ([0,1])     ([1,0])     = [1,1]
+-- (3) zipWith (+) ([0,1,1])   ([1,1,0])   = [1,2,1]
+-- (4) zipWith (+) ([0,1,2,1]) ([1,2,1,0]) = [1,3,3,1]
+-- ...
+pd :: [[Integer]]
+pd = iterate (\row -> zipWith (+) ([0] ++ row) (row ++ [0])) [1]
diff --git a/TestAufgabeFFP1.hs b/TestAufgabeFFP1.hs
index 1380c17..e119a3e 100644
--- a/TestAufgabeFFP1.hs
+++ b/TestAufgabeFFP1.hs
@@ -16,8 +16,18 @@ pof2sTests = TestList [pof2s1]
 
 -------------------------------------------------------------------------------
 
+pd1 :: Test
+pd1 = TestCase (assertEqual "pd" [[1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1],
+  [1,5,10,10,5,1], [1,6,15,20,15,6,1], [1,7,21,35,35,21,7,1],
+  [1,8,28,56,70,56,28,8,1], [1,9,36,84,126,126,84,36,9,1],
+  [1,10,45,120,210,252,210,120,45,10,1]] (take 11 pd))
+
+pdTests = TestList [pd1]
+
+-------------------------------------------------------------------------------
+
 tests :: [Test]
-tests = [pof2s1]
+tests = [pof2s1, pdTests]
 
 main = do
   forM tests $ \test ->