[pro] Compiler APIs in Common Lisp

[Matthew Swank]

I am current reading an interesting paper on Racket's macro system (referenced
here: http://lambda-the-ultimate.org/node/4196
), and some of the objects they expose quack like CLTL-2 Environments:
http://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node102.html. I have read that
having write access to environments makes it hard for the compiler to optimize
code. However, even portable read only access would be helpful. Does anyone
besides me and Cyrus Harmon (http://cyrusharmon.org/blog/display?id=113)
miss Environments?

Matt