[Haskell-cafe] Re: Haskell code for this example of flow control

2 Feb 2006


      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