G'day all.
Quoting Thomas Davie
To be honest, ghc compiles things so fast (at least on any of my systems) that I couldn't care less if it took 10 times as long (I would however like some added convenience for that time spent)
Have you ever compiled GHC itself? Just curious what you'd think about a 10x speed hit there. If it helps, think about the lifetime of a program. If you assume that a program grows linearly over time, and that recompilations occur at a roughly constant rate, it follows that the time spent recompiling is O(n^2). Constant factors matter.
If I compile a module on which lots of other modules depend, I have to do lots of recompilation... If I compile a module which is in a cyclic dependancy group, I have to do lots of recompilation, I don't see that there's a difference here.
If you only change the implementation of a module, not its interface, you don't need to recompile anything that imports it. (At least, this is true at -O0, which if you care about fast recompilation because you're deep in development, you're probably doing.)
That's a fair point about programming style, otoh, I don't think it's a reason to restrict users to not using cyclic dependancies.
As previously noted, cyclic dependencies alone aren't the problem. Cheers, Andrew Bromage