Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site sdcc7.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!genrad!decvax!ittatc!dcdwest!sdcsvax!sdcc3!sdcc7!ee178acb
From: ee178acb@sdcc7.UUCP (DARIN JOHNSON)
Newsgroups: net.lang
Subject: C++ help needed
Message-ID: <188@sdcc7.UUCP>
Date: Tue, 26-Nov-85 14:27:30 EST
Article-I.D.: sdcc7.188
Posted: Tue Nov 26 14:27:30 1985
Date-Received: Thu, 28-Nov-85 23:58:22 EST
Organization: U.C. San Diego, Academic Computer Center
Lines: 45
Keywords: separate compilation



A need a few answers to some C++ questions.  But first, a bug.
This code does not compile.  Moving class inner outside of class outer
will cause the thing to compile normally.

  class outer {
    class inner {
      int inner_data;
    };
    int outer_data;
  public:
    int inner_val(inner*);
  };

  int outer.inner_val(inner *x) {
    return x->inner_data;
  };

  I want to implement various forms of trees without letting the
application module know what type of trees they are.  This means
that the same header file should be the interface for all
implementations.  Distance fields should be invisible, as well as
whether binary, or B+ trees are used.  Is there a way to do this?
My solution was to use a #ifdef which to me is a hack.  Is there a
nice way to do this with a modula-2 type of interface?  In c, I did
this sort of thing simulating an Ada "private" type by having a
create function pass back a pointer to a structure, but the
application module thought this was a pointer to a char, int, or
whatever.  Is this type of thing do-able in C++  without using
"pure" c, but using the data-abstraction available?

  Also, when trying to do this sort of thing, I ran across the
problem of friend functions that I don't want the user to know
about.  For example, a merge function that the member functions
call, but which should be private to everyone else.  Is there a way
to do this?  

  C++ is a good improvement on many of c's limitations, but separate
compilation has a ways to go before is can place itself next to Ada
or modula-2, etc.

  Darin Johnson
  trying to figure it out before the students complain.
  sdcsvax!beowulf!wbreader