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

[Maurício]

   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.

   Thanks,
   Maurício