5.1 Changes in this release

5.1.3 General changes to Lisp

The Lisp implementation in this version of Liquid Common Lisp has the following new features:

A reorganization of underlying array implementation, for optimization and a better match with the FFI and C++.
True multitasking beneath I/O operations. This allows multiple independent listener windows from Lisp, and it improves management of the TTY.
The ability to redefinedefstruct structures with nearly as much functionality as redefining standard classes.

Liquid Common Lisp 5.0 Release and Installation Notes - 9 JUN 1997