Chez Scheme is a complete implementation of the language of
the Revised^6 Report on Scheme (R6RS), with numerous extensions.
It sports a fast compiler that generates native code for x86, x86_64,
and 32-bit PowerPC architectures.  Formerly a commercial product,
it was open-sourced by Cisco Systems in April 2016.

The unthreaded version is built by default, but enabling support for
multithreading is easy:
  THREADS=yes sh ./ChezScheme.SlackBuild

The full testing battery can also be run after the build completes.
  TEST=yes sh ./ChezScheme.SlackBuild
See the file BUILDING in the source distribution for more on
interpretting the 'make test' summary.
