The sample implementation depends not only on SRFI 128 but on:

• SRFI 1 (which can probably be got rid of if desired)
• SRFI 2 (ditto)
• SRFI 27 (which will definitely be gone at some point: I introduced it as a quick and dirty way to do double hashing in case of collision, but I’ll probably switch to Robin Hood or cuckoo hashing or some other faster technique)
• SRFI 133 (which could also go if someone desperately wanted an implementation without it)
• SRFI 151 (which is not going to go away)
• SRFI 160 base library (in theory it could be replaced with the R6RS bytevector library, but I would prefer not to)

dpk