7.4.1 RnRS

The r2rs, r3rs, r4rs, and r5rs features attempt to provide procedures and macros to bring a Scheme implementation to the desired version of Scheme.

Feature: r2rs

Requires features implementing procedures and optional procedures specified by Revised^2 Report on the Algorithmic Language Scheme; namely rev3-procedures and rev2-procedures.

Feature: r3rs

Requires features implementing procedures and optional procedures specified by Revised^3 Report on the Algorithmic Language Scheme; namely rev3-procedures.

Note: SLIB already mandates the r3rs procedures which can be portably implemented in r4rs implementations.

Feature: r4rs

Requires features implementing procedures and optional procedures specified by Revised^4 Report on the Algorithmic Language Scheme; namely rev4-optional-procedures.

Feature: r5rs

Requires features implementing procedures and optional procedures specified by Revised^5 Report on the Algorithmic Language Scheme; namely values, macro, and eval.