リスプ－１。

Whats your favorite Scheme standard nowadays, /prog/? Are you coding from a standard or implementation specific?

        1975 "Scheme: an interpreter for extended lambda calculus"
3 yrs   1978 RRS
     << 1984 SICP >>
7 yrs   1985 RRRS
1 yr    1986 R3RS
5 yrs   1991 R4RS
     << 1996 SICP 2nd E >>
7 yrs   1998 R5RS
     << 2001 HtDP >>
9 yrs   2007 R6RS
5 yrs   2012 R7RS-SmL-draft6

R5RS and earlier are the best. R6RS goes against the Scheme philosophy. The mandated IEEE floats and UTF-32 characters decrease portability. Portable languages should be sufficiently general and abstract to be implemented 100 years from now, like C89 is. Tying it down to specific binary representations is harmful. R7RS will be even worse once they replace continuations with more limited exceptions.
Programming languages should be designed not by piling feature on top of feature, but by removing the weaknesses and restrictions that make additional features appear necessary.