These documents are ratified by established standardization organizations. They exist outside the RnRS series but nevertheless closely follow the RnRS designs of their time. Despite the fact that these standards come from reputable organizations, they are now rarely used and mainly serve as historical curiosities. Virtually all Scheme implementers prefer the RnRS series.
Abbreviated IEEE Scheme, this standard was published by the Institute of Electrical and Electronics Engineers in 1990, reaffirmed with no changes in 2008, and withdrawn in 2019. The document number is IEEE 1178-1990.
IEEE Scheme is primarily based on R4RS. However, it incorporates a few
R5RS features: for example,
#f and '() are guaranteed to be
different objects. The standard has no macros.
Compliant implementations include Inlab Scheme and UMB Scheme.
Abbreviated DSSSL
ISO/IEC 10179:1996
DSSSL at OASIS Cover Pages with a comprehensive set of links