Things that implementations explicitly should do:
- Produce exact results from exact arguments passed to rational procedures
- Produce inexact results if exact results are not possible
- Use at least IEEE precision for transcendental operations
- Cause (exit #t) and (exit #f) to communicate success and failure to the operating system
- Use compactly represented integers as values of (current-jiffy)
- Document the mapping between library names and file names
- Permit redefinition or mutation of imported bindings (in the REPL only)