From: "Mike Miller"<MIKEMIL@vnet.ibm.com>
To: alexey@ccs.neu.edu
cc: lieber@ccs.neu.edu
Subject: HW3 part 5 question

In hw3, part 5 what does the "*l" represent in the class dictionary.  For
example:

ClassMethods = "{"  *l + [ <methods> SList(Method) ] - "}"

Also, what does the "+" and "-" represent.    I understand that the
ClassMethods type has an optional parameterized list  of Methods, and the
field name is methods. But the + and - are not inside quotes so they are
not syntactic sugar, so what are they for???

==================================

// For the Demeter/Java User's Guide: PrintingVisitor section.
// Also refer to this in cd section.

Often you would like to control the printing of your objects.
For example, you would like to use newline and space characters
to make your object sentences look nicer.

For example, if you write a compiler, you would like to represent
your assembly code as objects which you print at the end of the compilation. 
You want each assembly code instruction start on a new line.

The PrintVisitor is capable of handling this situation based
on information in the class dictionary. Wherever you can put a
lexical token in your class dictionary, you can put a pretty printing
command. 

There  are four printing commands that can be used:


*l        Add new line.

*s        Add space.

+         Indent.  Starts a new  indentation  level.  
	    Indentation is by three spaces by default.

-         Unindent.  Ends  the  current  indentation level.


Examples:

ClassParents = [*s "*extends*" *s Superclasses]
	       [*s "*implements*" *s Interfaces].
// we want a space before and after *extends* and *implements*.

TGVertex = ClassName *l 
	   "incoming:" *l + <incoming> List(TGEdge) - *l
	   ...
// we want a newline after the class name and "incoming"
// and print the edges indented. After the incoming
// edges are printed, we want another newline.


From dougo@ccs.neu.edu Tue Oct 28 19:06:04 1997
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Date: Tue, 28 Oct 1997 19:05:55 -0500 (EST)
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From: Doug Orleans <dougo@ccs.neu.edu>
To: Karl Lieberherr <lieber@ccs.neu.edu>
Cc: com3360@ccs.neu.edu
Subject: Re: pretty printing commands
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Addendum to the print-space directive:

Karl Lieberherr writes:
 > *s        Add space.

The PrintVisitor tries to be smart about spaces; it automatically
prints them between adjacent tokens that end/start with alphanumeric
characters.  For example,

    Foo = "foo" int Ident.

will be printed as "foo 3 bar", not "foo3bar".  However, in this
example:

 > ClassParents = [*s "*extends*" *s Superclasses]
 > 	       [*s "*implements*" *s Interfaces].

the *s directives explicitly print spaces before and after the
keywords because they don't start or end with alphanumerics.

The idea is (without any *s directives) to print the minimum number of
spaces necessary so that the object can be parsed back from the
printed string preserving the object structure.  (This is why the
PrintVisitor may be renamed to UnparseVisitor at some point in the
future...)

--Doug