From: http://www.haskell.org/haskellwiki/Blow_your_mind#Polynomials   -- splitting in two (alternating)   -- "1234567" -> ("1357", "246")   -- the lazy match with ~ is necessary for efficiency, especially enabling processing of infinite lists   foldr (\a ~(x,y) -> (a:y,x)) ([],[]) This works but can't find (~) operator anywhere. Please explain or site a reference. Michael