[Haskell-beginners] IO loops with tail call

6 Nov 2010

      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

then I thought it is not tail call because if expressions
return a value. (is it right?) So I changed a code:

echo "q" = return ()
echo xs  = do
  putStrLn xs
  xs' <- getLine
  echo xs'

but Monad connections are too complicated so that
I'm not sure it is tail call. Am I wrong?

Thank you!
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Yasuyuki Ogawa