implement pd

1 files changed, 16 insertions, 0 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]