<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">From: http://www.haskell.org/haskellwiki/Blow_your_mind#Polynomials<br><br> -- splitting in two (alternating)<br> -- "1234567" -> ("1357", "246")<br> -- the lazy match with ~ is necessary for efficiency, especially enabling processing of infinite lists<br> foldr (\a ~(x,y) -> (a:y,x)) ([],[])<br><br>This works but can't find (~) operator anywhere. Please explain or site a reference.<br><br>Michael<br><br></td></tr></table><br>