are you making many small calls, each of which modifies a small part of a large structure, and clojure is creating a new instance of the large structure each ti

are you making many small calls, each of which modifies a small part of a large structure, and clojure is creating a new instance of the large structure each time? that sounds like a pathological case for idiomatic clojure, but i would have thought you could work round it by keeping the data in a more "java like" format without too much pain. i've been using clojure for numerical processing this last few weeks and have been impressed how well it mixes lazy sequences and vectors. but i haven't had to face a case like you seem to be having.