On Sun, Nov 07, 2010 at 01:54:26AM +0900, Yasuyuki Ogawa wrote:
Hello!
I wrote a simple echo program which end up with input "q":
echo = do str <- getLine if (str == "q") then return () else putStrLn str >> echo
This is a tail call. Yes, if expressions return a value, but here nothing more is done with that value so the memory used by the current call to echo can be garbage collected once the recursive call is made. However, the real answer is: don't worry about it! Because of Haskell's lazy evaluation, the notion of "tail call" is not very important. And even if it were, you still shouldn't worry about it: just write your Haskell programs in the most natural, beautiful style you can think of. Maybe at some point down the road you will have to start worrying about optimization. But you should put it off as long as possible. -Brent