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