Haskell Quiz/PP Pascal/Solution Jethr0

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< Haskell Quiz‎ | PP Pascal
Revision as of 00:48, 21 December 2006 by JohannesAhlmann (talk | contribs) (using 3 spaces to make the triangle more symmetrical)
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Example: 

> pp_pascal 10
                      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


Solution: 

-- also using the pascal triangle function from [[Blow your Mind]]
pp_pascal n = unlines . map (center . showp) $ pascal
    where pascal   = take n $ iterate (\row -> zipWith (+) ([0] ++ row) (row ++ [0])) [1]
          showp    = concat . intersperse "   " . map show
          len      = length . showp $ last pascal
          center s = replicate ((len - (length s)) `div` 2) ' ' ++ s
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