I'm pretty sure that Haskell supports cyclic data structures and that GHC garbage collection is more complicated than that. See for example the presentation by

I'm pretty sure that Haskell supports cyclic data structures and that GHC garbage collection is more complicated than that. See for example the presentation by Ben Gamari over here: https://www.youtube.com/watch?v=EQqBpVRA3wU https://www.youtube.com/watch?v=EQqBpVRA3wU. Haskell GC is a generational copying design. Optionally you can enable the low-latency GC in newer runtimes, which is still generational and copying for the youngest generation but uses a parallel mark-and-sweep algorithm for the later generations.