s-expressionists/Concrete-Syntax-Tree

Concrete Syntax Trees represent s-expressions with source information

This library is intended to solve the problem of source tracking for
Common Lisp code.

By "source tracking", we mean that code elements that have a known
origin in the form of a position in a file or in an editor buffer are
associated with some kind of information about this origin.

Since the exact nature of such origin information depends on the
Common Lisp implementation and the purpose of wanting to track that
origin, we do not impose a particular structure of this information.
Instead, we provide utilities for manipulating source code in the form
of what we call concrete syntax trees (CSTs for short) that preserve
this information about the origin.

For example, we provide code utilities for canonicalizing
declarations, parsing lambda lists, separating declarations and
documentation strings and code bodies, checking whether a form is a
proper list, etc.  All these utilities manipulate the code in the form
of a CST, and provide CSTs as a result of the manipulation that
propagates the origin information as much as possible.

In particular, we provide an "intelligent macroexpander".  This
function takes an original CST and the result of macroexpanding the
RAW code version of that CST, and returns a new CST representing the
expanded code in such a way that as much as possible of the origin
information is preserved.