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Fyodor
Let me summarise the advantages of objects over procedure
variables you have pointed out (my words, not yours):
Advantage 1. "If someone unloads some of your modules while
you are still using them the o-o approach can terminate
(crash?) more gracefully. This doesn't actually work, but it
could work in theory if someone rewrote the compiler and
linker."
Advantage 2. "The documentation tools are just as convenient.
They aren't actually, but in theory they could be rewritten
to be as convenient."
Somehow I suspect that the average working engineer or
physicist would not be impressed.
Actually I don't believe advantage 2. I gave the example of
TextModels.dir.New. Since we know that dir is NOT (directly)
of type TextModels.Directory (since that is ABSTRACT) it is
often IMPOSSIBLE to find the correct Docu file for New other
than at run time. I guess that M.Cube could be a final type.
But this means that the user of the variable M.cube needs to
check the exact declaration of the type M.Cube just to
ascertain if the documentation search tool has a chance of
finding the correct Docu/Source/Interface for the procedure
M.Cube.Eval (I include interface because an extension may
have narrowed the return type).
There are no such subtleties to worry about with the function
R.Cube.
All this discussion convinces me even more that if a problem
is simple enough to be implemented with a function then a
function is the simple way to implement it.
So why is there a movement to ban procedure types at all?
I think it is down to history. Oberon used them to simulate
type bound procedures and allow polymorphism to be implemented.
When type bound procedures (methods) were introduced in
Oberon-2 it made THIS USE of procedure variables obsolete.
But don't ban all uses; that would be to throw out the baby
with the bathwater.
A comment on the argument that "Procedure types are redundant
and so should be eliminated". Where does this stop - when we
are all using Turing machines?
Regards
Robert
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