guest@mcgill-vision.UUCP (Ima Guest) (07/21/88)
I am presently using C with a library of functions for manipulating objects:
read/write/copy complex structures, lists, B-trees, arrays... I examined
C++ carefully in order to switch, because of the more elegant (and secure)
ways of manipulating objects, but i am still unsure about a few things.
If there are n types of objects and m types of grouping structures (lists...)
n*m declarations are necessary for strong type checking. However, these
declarations can be generated automatically using the preprocessor as
illustrated in Bjarne's C++ book. It is not clear to me how the methods
can be generated by the preprocessor for read/write/copy. The only way
i can think of is to write a more elaborate preprocessor that handles variable
length lists of arguments such as: ENUM(fruit,(apple,orange,raisin)) that
would give the proper declaration for the enumeration plus the methods to
read and write the symbolic names (case apple: cout << "apple";break; case or..)
(cin >> string; if(strcmp("apple",string) == 0) return(apple); if(strcmp("oran..
When reading an heterogenous list, the problem is even more severe. A string
that identifies the class of the object must be read and a "case" statement
is required for reading each of the possible types, then this pointer is
converted to the base class of the heterogenous list and the work is done.
The problem, though, is that the method to read the base class must contain
these "case" statements and therefore must know about all its derived classes,
which should normally be avoided.
Finally, browsing through objects is very useful. I understand that this
should not be bolted into C++ such that small programs can stay simple and
efficient but a hook for it may be really helpful. Methods to browse through
objects and nested lists and trees of objects would be as far as i can see
very difficult to build. Should the C++ compiler produce easily accessible
tables giving the name, type and offset of the members of structures such
that libraries for read/write/copy/browse could be supplied? Or should such
libraries use the information provided by the -g option on the C compiler?
Has anybody come up with neat solutions to these problems, are such support
libraries available (or coming)? I have heard of OOPS for C++, is it
available for ftp? Thanks in advance
Michel Dagenais
gaas@spock.ee.mcgill.ca