example of a possible space leak in lazy languages like Frege when running on a platform like JVM

Leak.fr

-- Leak example from http://homepages.inf.ed.ac.uk/wadler/papers/leak/leak.ps

-- convenience
parseStr :: String -> (String, String)
parseStr = packedPair . parse . unpacked where
	packedPair (x,y) = (packed x, packed y)       
               
parse :: [Char] -> ([Char], [Char])
parse [] = ([], [])
parse (' ': cs) = ([], cs)
parse ( c : cs) = ( c : fst b, snd b) where
	b = parse cs

surprise :: String -> String
surprise s = fst p ++ " surprise " ++ snd p where
	p = parseStr s

main _ = do 
	println $ parseStr "first next last" == ("first",  "next last")
	println $ surprise "first next last" == "first surprise next last"