[no subject]

[Bobrow.pa@Xerox.ARPA]

    1.  Packages should be used for coarse-grain control of 
    name conflicts, not fine-grain control.  In other words, I think 
    it's necessary to put the compiler, the window system, and 
    the mail system in separate packages, but I don't think we 
    should force a naive user writing a small program to spread 
    his identifiers among several packages simply because we 
    didn't give him proper scoping mechanisms for objects.

The naive user ought not to have to worry about the implementation. 
He ought merely to be able to state that an identifier should be 
protected.  An implementation with packages is sufficient 
(and can be easily understood by the user if needed).


   2.  An analogy.  Suppose function BAR modifies a global 
   variable N.  Function FOO, which calls BAR, innocently 
   binds a local N.  Should this break BAR?  Of course not;
   that's what lexical scoping is for.  No one would advocate 
   putting FOO's N and BAR's N in separate packages in this
    case; lexical scoping is a much more elegant solution.  

It is the case that one requires of a user that one declares a
variable N global, or at least special (or declares implicitly
or explicitly that FOO's N is local).  The same is true for the 
solution described above.  One shouldn't confuse user view 
and implementation.

   3.  Users should be AUTOMATICALLY protected from
   inadvertent name conflicts so they don't get screwed in 
   the ways I warned about in my proposal.

Our experience is that users know much more than you imply,
and usually are using name coincidence purposefully.  Implementors  
who use obvious names for "hidden variables" which are left 
unprotected are at fault.  They should use a "private"
declaration which could be implemented with a package
name.  Warnings on definitions that further specify named
variables are an easy add on.  One could distinguish the case in
which the user put the name conflict in the ":include option"
where they were clearly aware of it, and those which occur in
the body.

danny 


     ----- End Forwarded Messages -----