On Thu, 02 Sep 2010 12:15:27 +0200, Christoph wrote:
> Hi all,
>
> I just learned about closures in the Boost library and wanted to write
> some shorter code. To test, I used the following snippet:
>
> #include <iostream>
> #include <string>
>
> #include <boost/function.hpp>
> #include <boost/bind.hpp>
>
> class FakeVisitor {
> public:
> virtual void visit(int e) {}
> virtual void visit(std::string e) = 0;
> };
>
> template <typename T> class GenericVisitor : public FakeVisitor {
> public:
> boost::function<void (T e)> f;
> virtual void visit(T e) { f(e); }
> };
>
> void print(int a, int i) {
> std::cout << a << ":" << i << std::endl;
> }
>
> int main(int argc, char** argv) {
> GenericVisitor<int> v;
> v.f = boost::bind(&print, 0, _1);
>
> v.visit((int) 1);
> v.visit(std::string("hallo"));
> //boost::bind(print, 1, _1)(2);
> }
>
> Apparently, it does not work. Does anyone know why GenericVisitor<int>
> does not inherit visit(std::string)?
It does, but it's still declared a pure virtual function, i.e.
FakeVisitor (and GenericVisitor, too) is an abstract class that
cannot be instantiated. You would need to declare an implementation
of the visit(std::string) virtual method in GenericVisitor to make
it a non-abstract type.
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