[Haskell-cafe] Autrijus Tang interviewed by Perl.com

[Joel Reymont]

What is the meaning of xxs@(x:xs) in the code below?

I understand that x:xs is a list /head:tail/ but a tuple of (x:xs)  
does not make sense.

     main = print (take 1000 hamming)
     hamming = 1 : map (2*) hamming ~~ map (3*) hamming ~~ map (5*)  
hamming
         where
         xxs@(x:xs) ~~ yys@(y:ys)    -- To merge two streams:
             | x==y = (x : xs~~ys)   --  if the heads are common,  
take that
             | x<y  = (x : xs~~yys)  --  otherwise, take the smaller one
             | x>y  = (y : xxs~~ys)  --    and proceed to merge the rest

     Thanks, Joel