How to make a functor from a member function?
I want run
to call c.drive()
:
#include <functional>
using namespace std;
struct Car {
void drive() { }
};
template <typename Function>
void run(Function f) {
f();
}
int main() {
Car c;
run(bind1st(mem_fun(&Car::drive), &c));
return 0;
}
开发者_开发问答This does not compile and the error messages does not help me:
at f():
no match for call to ‘(std::binder1st<std::mem_fun_t<void, Car> >) ()’at the call to run:
no type named ‘first_argument_type’ in ‘class std::mem_fun_t<void, Car>’ no type named ‘second_argument_type’ in ‘class std::mem_fun_t<void, Car>’No boost please.
Update: even though the problem is solved, I would be very happy to see TR1/C++0x solutions!
The Boost/TR1/C++0x solution is quite straightforward:
run(std::bind(&Car::drive, &c));
bind1st
makes a unary function out of a binary function and a value. You are trying to make a function that takes no parameters out of a unary function and there isn't anything to support this in standard C++03.
You will have to do something like this.
template<class X, void (X::*p)()>
class MyFunctor
{
X& _x;
public:
MyFunctor(X& x) : _x( x ) {}
void operator()() const { (_x.*p)(); }
};
template <typename Function>
void run(Function f) {
f();
}
int main() {
Car c;
run(MyFunctor<Car, &Car::drive>(c));
return 0;
}
The C++0x solution using lambdas - http://www.ideone.com/jz5B1 :
struct Car {
void drive() { }
};
template <typename Function>
void run(Function f) {
f();
}
int main() {
Car c;
run( [&c](){ c.drive(); } );
return 0;
}
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