I tried to experiment with reactive[1] and rewrite NeHe tutorials using reactive-glut. However I run into problems. I tried to write first tutorial and exit on escape. However there were 2 problems: 1. Optimized constant functions 2. Continuous behaviour In reactive the final step is Behaviour which is 'function' from time to something a. Here a = IO (). The problem is that it is not indifferent how many time the same IO () was returned (we don't want to write to file twice etc.). I tried to workaround it in various ways but all I came up to was to switch after switch with time + * where * is the difference between times (unfortunately there is no function which give the next float). As with every tick everything is executed -- unless everything gets optimized to constant function. Am I failing to find proper docs? How solve those problems? If they are not easily solvable is there any general-purpose FRP library that allows to use IO inside? Regards [1] http://hackage.haskell.org/package/reactive