I disagree. I does not have to be unmaintainable. The difference between chaining map/filter and a single reduce is mostly a syntax transformation plus a little

I disagree. I does not have to be unmaintainable. The difference between chaining map/filter and a single reduce is mostly a syntax transformation plus a little bit of thinking upfront: ;; N.B.: Code was written here in a comment and never tested. ;; It might need some of those: ')))))' (flet ((filter-element (element bucket) ;; all (filter...)s of your chain here ) (mutate-element (element bucket) ;; apply all your (map...)s here )) (defun distill-magic (essence element) (if (not (filter-element element essence)) essence (cons (mutate-element element essence) essence)))) The hard part is sometimes to reformulate the chain in a way that you only filter on either pre- or post-mutation data. If you can't, your most probably using the wrong algorithm. But fixing that, if it requires serious thinking, is something I defer to the moment it actually matters. I now can, because it is neatly encapsulated in a single, local function definition. And yes, of course I can inspect intermediate results in a debugger: Just trace distill-magic or set a break point.