[kccqzy]

The problems brought about by the lazy evaluation (laziness when you don't want it) do not require architectural rewrites. It's mostly just profiling while setting a very low stack size limit, and then discovering which part of your code triggers a stack overflow. It can be solved by adding the right amount of seq (sequences evaluation), or ! (strict patterns). Maybe you'll also change a few incorrect uses of foldl into foldr. Even if you need to change from lazy Map to strict Map the change isn't disruptive; it's just changing some import and done; all the functions work. No architectural changes needed.