Hello all, I just split up a program I'm working on into several source files and ran into the following difficulty: module Process implements Process which has a field Runner. Runner is a basically a function which alters a 'System' state. So Process needs Runner, Runner needs System and thus Process needs System. module System implements among others a collection of Processes (because Processes can alter their states). So System needs Process. Eh voila, I have a loop. What I did was to leave the type of the Runner unspecified in Process, i.e. I now have (Process r) where r is the type of the Runner. Thus Process no longer needs to know about System. This does work, but it feels strange and I'm a bit worried that this is an indication for a design flaw, but I cannot see it.