chicken-scheme

Transducers for working with foldable data types.

Composable Scheme macro system based on the CK abstract machine

Immutable Lists (see: https://srfi.schemers.org/srfi-116/srfi-116.html)

Sets and Bags (see: https://srfi.schemers.org/srfi-113/srfi-113.html)

Flexible Scheme objects with message passing and prototypes