Yes, good points O(log n) cost. But that implies that elements have an ordering relation, no? Partial or total order. I have such structures that I use often, red-black trees that are purely functional implementations. So I understand your points here. But many times my data does not have any order relation, just an equality.
> On Dec 22, 2025, at 15:52, Scott L. Burson <[email protected]> wrote: > > On Mon, Dec 22, 2025, 12:20 PM David McClain <[email protected] > <mailto:[email protected]>> wrote: >> >> > BECOME takes a functional closure, which contains its state within the >> > closure vars. But I have become frustrated with too many BOA args, and I >> > also implemented a kind of dictionary to carry state with items labeled by >> > a keyword. > > > Right. I saw your file 'actor-state.lisp' and thought "Ah! This is a > functional map. This man needs FSet." > > Yes, the state is in the closure vars, but that doesn't preclude it being > large and complex. With functional data structures, you can efficiently > prepare an updated version of a large structure without invalidating the > previous version. If something goes wrong before the BECOME takes effect, no > harm has been done; the tentative new version simply becomes garbage. The > trick is to use only O(log n) space each time, where n is the size of the > previous version. > > -- Scott >
