I think you're looking for IORef http://www.haskell.org/ghc/docs/ latest/html/libraries/base/Data-IORef.html Something like this (untested) should do what you want: example :: IO () example = do { ref <- newIORef 1000; loop ref } where loop ref = do x <- readIORef ref print x when (x>1) (writeIORef ref (x/2) >> loop ref) On Feb 2, 2006, at 10:57 AM, Maurício wrote:
Donald Bruce Stewart wrote:
briqueabraque:
Hi,
I would like to know what options I have in Haskell to do something similar to this C++ code:
double a = 1000; while (a>1) a/=2;
I'm able to do that with lists, but I would like to know how to do that with monads and variables with state. You'll get good code using a normal recusive loop: main = print (loop 1000) where loop a | a <= 1 = a | otherwise = loop (a/2) All such control structures may be implemented using recursion. -- Don
I understand those examples, but I really would like to know how to do that with monads. I would like to ask the same question, but now with this code:
double a = 1000; double b = 0; while (a != b) { a /= 2; cout << a; // Prints a cin << b; // User gives a number, stored in b };
Best, Maurício
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