This library serves as the basis of cloture[0] an effort to host Clojure on Common Lisp. I hope to see both projects thrive!

[0] https://github.com/ruricolist/cloture

Balancing trade-off is crucial in software design. It would be nice if the documentation listed the trade-offs of the structures compared to their native implementations. I imagine at least every mutation is consing? There are also larger fixed and slow-growing overheads in various operations.

Persistent/functional data-structures aside, bags are the most useful data type that is omitted from many container-libraries (whether or not the containers are part of the language stdlib).

I remember watching you give a version of this talk at the Bay Area Lisp meetup!

Nice thanks, is there a single-HTML-page view available by any chance?

Just FYI, this section at the end about R6RS Scheme is a little confused: https://fset.common-lisp.dev/Modern-CL/Top_html/Scheme-_0028...

   Strings are immutable [in Scheme]. Functional point update operations are not provided, presumably out of time complexity concerns, but string-append and substring are provided, and there are functions to convert to and from lists of characters; I guess the idea is that fine-grained string construction will be done using lists and then converted. Amusingly, there’s string-copy, though it’s hard to see why one would ever use it.

Strings are actually mutable in R6RS. See https://www.r6rs.org/final/html/r6rs/r6rs-Z-H-14.html#node_s... - there is an imperative update-in-place function which mutates the argument. So of course string-copy really is useful, you might want to mutate a string and keep an unaltered copy. And the intent of string->list is to automatically let your list-processing code become string-processing code. It is way too strong to say "Functional point update operations are not provided, presumably out of time complexity concerns" - R6RS actively encourages functional operations on strings by calling string->list first, even though that's O(n) overhead.

The overall point you are making seems clearly correct: R6RS Scheme does not provide any "mostly functional" datatypes beyond basic s-expressions, so it would take a lot of work to develop Clojure/FSet-style tools. But it's strange to so badly misstate what strings in Scheme are like.

Hidden 13 paragraphs down the third page is the first actual description of the project:

> So FSet has a dual mission: first, to bring Common Lisp up to date, by giving it a much richer ensemble of functional collection data structures, to greatly expand the space of algorithms that can be written in an elegant functional style and still run efficiently; and second, as with Clojure, to support and encourage the use of functional collections for general programming.

Cool project but the docs could be greatly improved by putting the purpose of the project front and center. Don't make readers guess.

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