My thoughts on design patterns

In many programming languages design pattern is a hot topic and a must do; without mastering various deisng patterns one seems barely mastered the programming language. My take is if design patterns is really essential, why it isn't built as part of the programming language, and enforce everyone to use it? After all, it's good to encourage good behaviors than bad.

In Functional Programming language, design pattern isn't frequently talked about, as it has quite different programming paradigm, For the reason I listed, the essence of design pattern (I wouldn't like to name it, the word design is much more prefered) is built into the programming languge.

I woud like to elaborate more reason behind that, however, some expert already did a much better job (Yet I'm just a beginner).

http://blog.ezyang.com/2010/05/design-patterns-in-haskel/

Why you should learn functional programming

The first time I came across functional programming is from wikipedia accidentally, for a quick sort example:

quicksort [] = []
quicksort (x:xs) = quicksort left ++ [x] ++ quicksort right
    where left = filter (<= x) xs
          right = filter (> x) xs

I was amazed (even today) by its simplicity, and come into the problem deeply without distracted by any kind of implementation details. before that I've spent quit sometime to understand quick sort, mainly by reading text book Introduction to Algorithms (It's a great book). However, it was the Haskell version helped me understand the algorithm deeply in mind.

Another example is finding /nth/ maximum element of an list, this is very similar to quicksort, except we can discard either left or right:

kth n (x:xs)
  | n <= len = kth n right
  | n == 1 + len = x
  | otherwise = kth (n - len - 1) left
    where left = filter (<= x) xs
          right = filter (> x) xs
          len = length right

Thus it requires less time complexity (average time complexity is O(n)). And I think it's more easier for understanding the problem.