Fellow Functionally-Caffeinated, i have a few questions regarding copy-on-write semantics. i am working for a client that is stuck with a legacy in-house language that chose copy-on-write as a way to provide aliasing-issue-free semantics to a user population they perceived as not sophisticated in programming. Despite the fact that they are now realizing there are a lot of very sophisticated and performant ways of providing ways to avoid aliasing problems, they are stuck having to support copy-on-write for legacy codes. So, i have two basic questions. First, has anyone worked out a monadic approach to copy-on-write? (And, Is there any analysis of perf characteristics of said monadic schemes?) Second, i have worked out a scheme which is like a version control system. The mutable collection is treated like a source tree. A reference to a mutable collection is like a tag for a branch of the tree. Updates attach deltas to a given branch of the tree. Accesses have to be matched to see if they are impacted by any update-deltas. There is an optimization/memo-ization strategy in which certain events (access or update) trigger a copy to be made, finally, and the updates applied to the copy. This shifts perf characteristics so that access becomes slower and update considerably faster in the common case. Does anyone know if such a scheme has been studied? i'd like to compare implementations, too, if possible. Best wishes, --greg -- L.G. Meredith Managing Partner Biosimilarity LLC 505 N 72nd St Seattle, WA 98103 +1 206.650.3740 http://biosimilarity.blogspot.com