Doug Orleans has implemented edge visitors and other nice
features. The new version has been installed and is available
through j-gen-make and make.

More information on edge visitors is in:

http://www.ccs.neu.edu/research/demeter/course/f96/APbookWithDemJava.html
search for "Edge visitors".

A simple example of an edge visitor:

before -> *,*,* (@ System.out.println(" going through edge from "
  + source.getClass().getName() + " to "
      + dest.getClass().getName() + " labeled "
	    + edge); @)

Edge visitors are a very important improvement to adaptive programming
with Demeter/Java.

-- Karl Lieberherr

===================
Date: Tue, 4 Feb 1997 13:12:53 -0500 (EST)
From: Doug Orleans <dougo@ccs.neu.edu>
To: lieber@ccs.neu.edu
cc: ghulten@ccs.neu.edu, lth@ccs.neu.edu, johan@ccs.neu.edu, kedar@ccs.neu.edu,
        binoy@ccs.neu.edu, dougo@ccs.neu.edu
Subject: new version of demjava

I have uploaded the newest version of demjava into
/proj/demsys/demjava/src-0.4.1 and classes/demeter-0.4.1.  There are
four changes (I think):

    + Edge wrappers!  You should now be able to attach a before or
      after method to an edge glob, e.g.

	before -> *,foo,* (@ /* ... */ @)

      will be called whenever a construction edge named "foo" is about
      to be traversed.  You can also attach to alternation and
      inheritance edges.  Inside such a method, the variables "source"
      and "dest" will contain the source and dest objects of the edge
      (similar to "host" in class-attached methods); also, in the case
      of construction edges, the variable "edge", of type String, will
      contain the name of the edge being traversed.  (Look at the
      generated source code if you're confused as to what's going on.)
      You can also attach before and after methods to a set of classes
      and/or edges with the { , } construction.

    + Behavior can be attached to multiple classes at once, e.g.

	{ Foo, Bar } {
	    traversal allBaz() { to Baz; }
	}

      will generate two traversals, one attached to Foo and one
      attached to Bar.  This applies to before and after methods as
      well as verbatim methods.

    + Class defs are now kept in a hash table, which speeds up
      the program quite a bit (especially for large input files).
      There are no other external effects of this change.

    + The generated grammar file sets the option JAVA_UNICODE_ESCAPE,
      which causes Jack to generate a lexer that can recognize Unicode
      escapes (e.g. \u0123).  This is a very minor change, but it
      means that you'll have to change your Makefile to replace
      ASCII_CharStream.java with ASCII_UCodeESC_CharStream.java.  The
      new Makefile.template (which is copied by j-gen-make) will do
      the right thing.

I'm reasonably confident that the new version is fully
backward-compatible with 0.4 (except for the ASCII_UCodeESC_CharStream
thing)-- mainly because it compiles itself.  However, Karl, please
test it out before switching the symbolic links.  Also, edge wrappers
have not been tested very thoroughly, so please try them out and let
me know how it works.  This is only a first cut at a design, so if you
have a better idea as to how they should work, please let me know.

--Doug