@abcdw@fosstodon.org From what I understand, Hash tables are part of the R7RS-Large standard, which has not yet been finalized (R7RS-Small has been finalized as of 2013). According to the R7RS-Large document, it has been decided that hash tables will be implemented as part of the standard according to SRFI-125

Check out Section 3.3 of the R7RS-large "Red" document, and also check out the notes . Any Scheme implementation you use that implements SRFI-125 will already be compliant with the new standard. Also note at the beginning of the doucment there is a section called "Red Edition Ballot Results", on page 8 (item 7) they mention that SRFI-125 was voted on to be included in the standard.