Conference turris::languages

    
    I also have a modula-3 question - what do they mean by traced and
    untraced objects?
    
    dc

    From my limited understanding ,
    
    traced == eligible for garbage collection
    
    untraced is not.
    
    /Ashok
    

    re: .0, .2
    
    You answered it yourself. Modula-3 does not support multiple
    inheritance. Even though the concept is similar to classes in other
    languages, there are several important differences. You may want to
    read the following Wirth's papers on which, I think, the objects in
    Modula-3 are based. I agree that the report is concise and some
    sections do need further clarification; overall, I think it is a
    commendable job. If you have read Paul Rovner's paper before, you will
    find the report easier to understand. 

    You are right regarding the difference between traced and unbtraced
    objects. Greg Nelson, one of the designers of Modula-3, believes that
    more and more programs in future will rely extensively on automatic
    garbage collection. I think he is right; it keeps the programs safe and
    the programmer is not burdened with keeping track of
    allocation/deallocation. However, due to performance reasons or
    otherwise, one doesn't want to have the objects traced. Greg says that
    in building the SRC window system, they used traced references
    everywhere except in a couple of places at the lowest level and thus
    kept the programs safe without loss of performance. 

    Even though Modula-3 is a strongly typed language it has some problems
    regarding type equivalence. An accidental type equivalence may weaken
    the power of strong typechecking. I understand that the design is being
    changed to remedy this problem. 

    Hanuma

 
%A N. Wirth
%T From Modula to Oberon
%J Software-Practice and Experience
%V 18
%N 7
%D July 1988
%P 661-670
%K OOP, programming languages
 
%A N. Wirth
%T Type Extensions
%J ACM Transactions on Programming Languages and Systems
%V 10
%N 2
%D April 1988
%P 204-214
%K data types, data abstraction, OOP

    Does anyone have the Modula-3 language definition on-line?  This
    is the first I've heard of Modula-3, and I'd very much like to find
    out more.  Failing an on-line copy, how about a pointer that our
    library would understand?
    
    John
    
    PS: After several years of Algol-68 programming, I agree wholeheartedly
    with the comments of .-1 about automatic garbage-collection.  The
    benefits in programmer productivity (and error-free programs) that
    being able to forget about storage reclamation brings far outweigh
    the small loss of performance that automatic garbage-collection
    causes, especially if the programmer can cause the garbage-collector
    to be invoked at times when he knows there is likely to be a lot
    of reclaimable storage.  Recent developments in continuously scanning
    garbage-collection algorithms for distributed systems offer the
    possibility of reducing the performance penalty of automatic storage
    reclamation still further.

             
    You can copy the report from
    
    cookie::disk$fig_2:[kodavalla.public.src]t23_modula3_report.ps
    
    .txt is also there in the same directory.
    
    It is SRC Research Report 23; you or your library can obtain SRC
    reports by writing to:
    
    SRC Research Center
    130 Lytton Avenue
    Palo Alto
    CA 94301
    

    I'm  wondering about the lack of multiple inheritance in Modula-3.
    I keep running into a need for it even in C++ which I'm currently
    learning and which lacks the feature as well (current version).
    May be I haven't yet learned how to properly define objects.
    
    Is multiple inheritance generally considered unnecessary or a "frill"
    in OOLs ? If not, why did Modula-3 leave it out ? If yes, how does
    get around the need for it ?
    
    /Ashok

The SRC keeps a conference with all their research abstracts....