It's a Common Lisp library for advanced forms of iteration.
It is inspired by iterate, and is in fact mostly a rewrite of it using a proper code walker.
Iterate has all kinds of issues, mostly around code walking. It was causing us trouble when we used it inside delimited continuations, or inside the query compiler in hu.dwim.perec (e.g. it is not extending the lexical environment with the variables it is introducing).
Iterate also loses SEXP identity,
and because of that Slime's debugger cannot jump to the forms when the code is
inside an iterate form. This codebase does its best to retain the identities.
It was also quite a lot of fun working on it. The ultimate goal was to put together a library that has an improved API compared to Iterate, and also a compatibility layer so that it can be used as a drop-in replacement for Iterate.
Written by attila@lendvai.name.
The primary communication channel is the facilities on the project's GitHub page.
Unfortunately, I ran out of steam at around 80% completion, and the project has been abandoned for years.
You're welcome to take over development if you feel inspired!
What works is of good quality, and the infrastructure is also solid. It has a good test system, too. IOW, the depth-work is mostly done, but there's more breadth-work to be done.