Appendix A Release Notes

The previous full release of MIT/GNU Scheme was version 7.6.1. This section describes changes that have occurred since that time. For more detailed information, see the ChangeLog files in the source code.

Note that MIT/GNU Scheme still conforms to the Revised^4 Report on the Algorithmic Language Scheme, but not to the Revised^5 Report on The Algorithmic Language Scheme.

These are the changes since release 7.7.0:

• Release 7.7.1 fixes several bugs in IMAIL; fixes a bug that prevented the use of server sockets on Windows systems; and fixes a bug that caused the debugger to generate errors in common circumstances.
• Release 7.7.0 provides “hygienic” macro support, as defined in R^4RS and R^5RS. This is a complete rewrite of the syntax engine, so any program that uses macros should be rewritten to use the new engine. A subset of the old macro-definition syntax is still supported, but this will eventually be removed. Note that the new syntax engine has no effect on the compiled-code format; most binaries compiled by release 7.6.x should continue to work.

  There are several user-visible consequences to this change:

  • These syntactic keywords have been eliminated: define-macro, in-package, macro, make-environment, scode-quote, unassigned?, and using-syntax.
  • The syntactic keyword the-environment has been restricted to use in top-level environments. It is no longer allowed in the body of any binding form (e.g. lambda, let).
  • Syntactic keywords are now stored in environments, rather than in a separate syntax-table structure. The environment abstraction has been enhanced to support this, as well as to make it more general. The changes are documented in the reference manual.
  • The syntax-table abstraction has been eliminated, and most procedures and arguments involving syntax tables have been removed. One exception is the load procedure, which still accepts a syntax-table argument, but ignores it.

  Although the 7.6.1 release had a workaround for problems with certain AMD Athlon processors, the workaround was ineffective on machines running Windows operating systems (and possibly OS/2 systems as well). This version fixes that problem.

  The hash-table abstraction is now always loaded. It's not necessary to call load-option prior to use of hash tables. For upwards compatibility, calling ‘(load-option 'hash-table)’ is still permitted but does nothing.