Am Sa., 26. Sept. 2020 um 18:31 Uhr schrieb Felix Thibault
<xxxxxx@gmail.com>:

> That's what I was wondering about , several of the srfi-206 libraries start off like:
>
> (define-library (...)
>   (export ...)
>   (cond-expand
>     (else
>        ...)))
>
> and I'm not familiar with this idiom- is this just pre-emptive, so that it's easier for people down the line to add implementation-specific code if they need to, or is there some other purpose so that I can't convert to r6rs just by removing the cond-expands?

Yes, just pre-emptive or as a placeholder. The else clauses of the
SRFI 206 libraries are for the poor-man's-implementation.
Implementation-specific code can be put before that line.

(If you need a complete implementation of SRFI 206 to test against, I
have added it into Unsyntax. (It will always use its internal
library.))