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.