On Tue, Jul 20, 2021 at 1:54 PM Marc Nieper-Wißkirchen <xxxxxx@nieper-wisskirchen.de> wrote:

 

(1) No user can later register plists because the empty list is already registered as an alist, meaning that SRFI 225 won't be able to support all well-known Scheme/Lisp dictionary types.

True.  But the use of plists in Scheme is still minimal, and in CL they are mainly used in order to handle function calls with keywords that have not been specified in advance (defining a function with &allow-other-keys turns off compile-time keyword checking).  Plists don't really have any advantages as general-purpose key-value stores over alists.

(2) Alists are still restricted to the `equal?' key comparator, which is too restrictive for general code.  One can try to remedy this by adding just another dynamically scoped parameter, say, `current-alist-equality-predicate' but this makes reasoning even harder and can cause a further slow-down. Moreover, it will become inconvenient as soon as code has to deal with two different types of alists in parallel.er by light years.

We really need a way to attach a comparator to an alist, but I don't see how, unless by consing it onto the alist.