Re: New release of the Dynace OO extension to C

Juha Nieminen <nospam@thanks.invalid>
Mon, 20 Jul 2009 21:22:19 GMT
Richard Harter wrote:

Perhaps you could elaborate on your thought just a bit. In C it is easy
enough to write the equivalent of constructors and destructors.

  The major difference is that in C you always have to call the
destructors manually, as there is no way to automatize destructor calls
when objects go out of scope.

  And it's not only destructors which help with memory management.
Automatic copy constructor and assignment operator calls also help.
That's the reason why I can, for example, read some input data into
strings, throw the strings into an STL data container, and then
basically forget about them. I don't need to worry about how or when
those strings should be destroyed.

  Moreover, if I'm making my own abstract data container (ie. abstract
in the sense that it can contain any copyable type, iow. it's
templated), I don't need to worry about the internal memory management
of the objects being stored. They do their thing internally, and I just
create, copy, assign and destroy them. If the type in question happens
to be a string, it doesn't matter from the point of view of my data

  This is one of the reasons why it's so hard to make generic data
containers in C: Memory management. The container itself would have to
be aware of memory management issues of the objects being stored. It
cannot be abstracted away into the innards of the object's type. In C++
the container only has to care about its own memory management, it
doesn't have to care about the internal memory management of the objects
being stored.

  For example, if you create a std::set<std::string>, the std::set here
doesn't "know" how std::string behaves internally or how it manages its
own memory. It doesn't have to. That's the whole beauty of abstraction
and RAII. It's, in fact, so beautifully abstracted that you can even
give the set eg. internal types (which do not allocate nor manage memory
in any way), eg. you can have a std::set<int>, and it will still work
just fine.

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