Chibi-Scheme is a very small library intended for use as an extension and scripting language in C programs. In addition to support for lightweight VM-based threads, each VM itself runs in an isolated heap allowing multiple VMs to run simultaneously in different OS threads. The default language is R7RS Scheme, including first-class continuations and low-and-high-level hygienic macros.

The current release is 0.5.3, "Boron," which includes the following changes:

• draft R7RS "small" support
• image file support for fast loading
• support for complex numbers and exact ratios
• {brace} syntax for user-defined type literals
• better OOM handling and memory tests (now valgrind safe)

and many others. Most features are optional at compile time. A full-featured build produces a library just under 200kb, whereas a minimal build can be under 80kb.

Chibi-Scheme is known to work on 32 and 64-bit Linux, FreeBSD and OS X, Plan9, Windows (using Cygwin) and iOS.

See the user manual for more details:

http://synthcode.com/scheme/chibi/

Future releases should come at a faster pace now. Near-term goals include native x86 support, batch compilation, and alternate language support.