On Sat, Apr 13, 2019 at 4:53 PM John Cowan <xxxxxx@ccil.org> wrote:
It occurs to me that I've been assuming that the requirements for a SRFI sample implementation allow you to point to one or more existing implementaitons ("prior art").  Of course, that doesn't necessarily help other implementers.

What do people think? 

The SRFI Process document explains that that is allowed, but not preferred:

It must contain a sample implementation. This requirement may be met (in order from the most to the least preferred) by:
  1. A portable Scheme implementation (possibly using earlier SRFIs). This is the most desirable option, because then implementors can provide a (possibly slow) implementation with no effort.
  2. A mostly-portable solution that uses some kind of hooks provided in some Scheme interpreter/compiler. In this case, a detailed specification of the hooks must be included so that the SRFI is self-contained.
  3. An implementation-specific solution. Ideally, tricky issues that had to be dealt with in the implementation will be identified.
  4. A separately available implementation, where a sample implementation is large or requires extensive modifications (rather than just additions) to an existing implementation. This implementation will eventually be archived along with the SRFI and the discussion related to it.
  5. An outline of how it might be implemented. This should be considered a last resort, and in this case the rationale for the feature must be stronger.