--  :load "c:\\HaskellProgs\\chap6.hs"   

and' [] = True
and' (True:r) = and' r
and' _ = False

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concat' [] = []
concat' (l:ls) = l ++ (concat' ls)

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repl 0 _ = []
repl n item = item:(repl (n-1) item)

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nth 0 (h:t) = h
nth n (_:t) = nth (n-1) t

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elem' _ [] = False
elem' a (h:t) | a == h    = True 
              | otherwise = elem' a t
			 
------------------------------			 
			 
merge [] l    = l
merge l  []   = l	
merge (a:b) (c:d) | a<c       = a:(merge b (c:d))	
                  | otherwise =	c:(merge (a:b) d)
				  
------------------------------				  
				  
msort [] = []	
msort [a] = [a]
msort list = merge (msort (take half list))	(msort (drop half list))	
             where
                half = (length list) `div` 2