On Wed, 21 Dec 2005, Peter Simons wrote:
Some example for writing a text the IO oriented way: do putStrLn "bla" replicateM 5 (putStrLn "blub") putStrLn "end"
whereas the lazy way is putStr (unlines (["bla"] ++ replicate 5 "blub" ++ ["end"]))
Um, maybe it's just me, but I think the first program is far superior to the second one. The last thing you want your I/O code to be is lazy. You want the exact opposite: you want it to be as strict as possible. Not only does the second version waste a lot of CPU time and memory for pointlessly constructing a lazily evaluated list nobody ever needs, it will also explode into your face the moment you use that approach to write any non-trivial number of bytes.
Surely the actual explosion comes about because PutStr forces the lot at once? If PutStr were to evaluate a character at a time, the laziness would be slow and spew a lot of garbage to collect but not hang on to as much space as you suggest. Not to say that the strict solution isn't still more efficient, of course. -- flippa@flippac.org The task of the academic is not to scale great intellectual mountains, but to flatten them.