On Wednesday, 2 April 2014 at 18:14:46 UTC, Steve Teale wrote:
But both of these approaches are clumsy compared to what I
would like to see.
Yeah, I think it would need language support to be worthwhile in
the long run. I think it makes a lot of sense for constructors
that the superclass has the first and last word in what the
object should look like. E.g. let subclasses populate an array in
their "inner-clauses" and let the superclass verify it or
compile it into something efficient.
However, it does require a sensible super class design since you
don't override virtual functions, but merely extend them.
I'm pleased to see though that some other languages have noted
this deficiency.
Yup, I am not sure if the inner clause was in Simula I in 1963,
but I believe it must have been present in Simula67. It was also
used for prefixing of blocks in Simula so that you could open
"libraries" by turning a class into a scope. E.g.
class MyToolkit begin
integer filehandler;
methods like print()
filehandler = openstuff();
inner;
closestuff(filehandler);
end
// and use it as
MyTookit begin
print() // file is open, we can print here
end
As Simula was Bjarne Stroustrup's influence for C++ he really
does not have an excuse for not adopting this stuff. ;-) Well, I
guess RAII is his version of "inner"…
If you had virtual types as class members then I guess you could
emulate inner with RAII like patterns. (By instantiating the
class rather than doing a function call and let the constructor
and destructor wrap the "inner")
