Fast-alist-free-on-exit
Free a fast alist after the completion of some form.
Logically, (fast-alist-free-on-exit alist form) is the
identity and returns form. Also see fast-alist-free.
Under the hood, this essentially expands to:
(prog1 form
(fast-alist-free alist))
In other words, alist is not freed immediately, but instead remains a
fast alist until the form completes. This may be useful when you are writing
code that uses a fast alist but has many return points.
See also the macro fast-alists-free-on-exit defined in the community
book "books/centaur/misc/hons-extra.lisp", which can be used to free
several alists.
The community book "books/centaur/misc/hons-extra.lisp" extends the
b* macro with the free-on-exit pattern binder. That is, after
executing (include-book "centaur/misc/hons-extra.lisp" :dir :system),
the form
(b* (...
((free-on-exit a b c))
...)
...)
causes a, b, and c to be freed when the b* completes,
but they remain fast alists until then.
