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From: gary@neptune.ctc.contel.com (Gary Bisaga  x4219)
Newsgroups: comp.lang.c++
Subject: Re: Migrating from FORTRAN to C++
Message-ID: <1991May29.074130@neptune.ctc.contel.com>
Date: 29 May 91 11:41:30 GMT
References: <91147.181437U10215@uicvm.uic.edu>
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In article <91147.181437U10215@uicvm.uic.edu>, U10215@uicvm.uic.edu writes:
> Recently I bought a Borland c++; but I have never programmed in c++.
I believe this is a good choice.  I too have bought BC++ and both the product
and the documentation seem to be quite good.

> One thing really bothers me for learning this language.
> Is there any way of using FORTRAN COMMON statement in c++?
Well ... the "obvious" solution (unless you're not a C programmer) is to use
global variables, ones declared outside of any function.  I am assuming, however
that you want something a little better than variables accessible to ANY function,
analogous to FORTRAN's named COMMON.  There are at least a few ways of doing this.

First, you can use variables declared STATIC.  This keeps the variables only accessible
to functions in that same source file.  This is also an "obvious" C language method.

Second, since named COMMON is sort of a data hiding mechanism, you could create
a class for each named COMMON you use.  Use private member variables for the variables
in the named COMMON; make member or friend functions of the functions that use the
named commons.  Using multiple inheritance could make this more complete -- have
classes that multiply inherit where a function needs groups of named COMMONS.

Probably the best advice is to try not to do a direct comparison between COMMON and
C++ constructs.  Acknowledge that COMMON provides a combination data sharing and
data hiding mechanism and look to see how C++ does the same two jobs (classes and
inheritance).  These can be very powerful once you get used to the object oriented
"idea."

If you want to know more about object-oriented development in general, I highly
recommend the book "Object-Oriented Analysis", Second Edition, by Peter Coad.  It's
part of the Yourdon series, published by Prentice-Hall (ISBN 0-13-629981-4).  He
and Ed Yourdon also have a forthcoming book about object-oriented design that will
probably be good as well.

Gary Bisaga (gary@ctc.contel.com)