chezscheme - 9.5.4+dfsg-4 main

Chez Scheme is both a programming language and an implementation of
that language, with supporting tools and documentation.
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As a superset of the language described in the Revised^6 Report on
the Algorithmic Language Scheme (R6RS), Chez Scheme supports all
standard features of Scheme, including first-class procedures, proper
treatment of tail calls, continuations, user-defined records,
libraries, exceptions, and hygienic macro expansion.
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Chez Scheme also includes extensive support for interfacing with C
and other languages, support for multiple threads possibly running on
multiple cores, non-blocking I/O, and many other features.