is it possible to bind 2 default parameters using function object(STL)?

[thinktwice]

here is what i what to do;
//pesudo code
iter = container.begin();
while (iter != container.end())
{
myclass *obj =my_cast (*iter);
obj->func(arg1, arg2);
}

i want to simplify those code just like this:
std::for_each(conatiner.begin(), conatiner.end(), ???)

is it possible? how to achieve?
thanks in advance

 

[n2xssvv g02gfr12930]

here is what i what to do;
//pesudo code
iter = container.begin();
while (iter != container.end())
{
myclass *obj =my_cast (*iter);
obj->func(arg1, arg2);
}

i want to simplify those code just like this:
std::for_each(conatiner.begin(), conatiner.end(), ???)

is it possible? how to achieve?
thanks in advance

What you probably need is a Functor object. Something like the code below:

class FunctorExample
{
private:
int arg2;
Obj &Data;
public:
FunctorExample(Obj &Ref, int Val) : Data(Ref),arg2(val) {}
void operator() (int arg1)
{
Data.func(arg1,arg2);
}
};

{
// Some sample code
Obj ExampleObj;
FunctorExample FnctObj(ExampleObj,6);
std::for_each(container.begin(),container.end(),&FnctObj);
}

With a more accurate description/example of your requirements
this could probably be modified to suit.

JB

 

[Alex Beluga]

here is what i what to do;
...horrible for loop code eaten out
i want to simplify those code just like this:
std::for_each(conatiner.begin(), conatiner.end(), ???)

is it possible? how to achieve?
thanks in advance

Hello.
First, use Boost, Boost is your friend, Boost won't harm you More
specifically, I'd recommend you to use Boost.Bind for simplicity sake.
Second, you should've probably use mem_fn here as you're referring to
the obj's class namespace.
Here what kind of pseudocode you should be left over with:
std::for_each(container.begin(),container.end(),
boost::bind<ReturnType>(mem_fn(&myclass::func,arg1,arg2)));

 

[Victor Bazarov]

here is what i what to do;
//pesudo code
iter = container.begin();
while (iter != container.end())
{
myclass *obj =my_cast (*iter);
obj->func(arg1, arg2);
}

i want to simplify those code just like this:
std::for_each(conatiner.begin(), conatiner.end(), ???)

is it possible? how to achieve?

It's possible if you write your own functor. The standard means only
exist for no- and one-argument member functions.

#include <iostream>
#include <functional>
#include <algorithm>
#include <vector>
using namespace std;

struct foo {
void bar(int one, double two) {
cout << this << " : " << one << " and " << two << endl;
}
};

template<class T, class A1, class A2> struct mem_fun_2_t {
void (T::*memptr)(A1, A2);
A1 arg1;
A2 arg2;
mem_fun_2_t(void (T::*mp)(A1, A2), A1 a1, A2 a2)
: memptr(mp), arg1(a1), arg2(a2) {}
void operator()(T& t) { return (t.*memptr)(arg1, arg2); }
};

template<class T, class A1, class A2>
mem_fun_2_t<T,A1,A2> mem_fun_2(void (T::*mp)(A1, A2), A1 a1, A2 a2)
{
return mem_fun_2_t<T,A1,A2>(mp, a1, a2);
}

int main()
{
vector<foo> v(10);
for_each(v.begin(), v.end(), mem_fun_2(&foo::bar, 42, 3.14159));
}

 

[Jeff Flinn]

Hello.
First, use Boost, Boost is your friend, Boost won't harm you More
specifically, I'd recommend you to use Boost.Bind for simplicity sake.
Second, you should've probably use mem_fn here as you're referring to
the obj's class namespace.
Here what kind of pseudocode you should be left over with:
std::for_each(container.begin(),container.end(),
boost::bind<ReturnType>(mem_fn(&myclass::func,arg1,arg2)));

Not quite.

boost::bind( &myclass::func, _1, arg1, arg2 ) );

There are very few cases where ReturnType needs to be explicitly specified,
mem_fn is not necessary, and you forgot that member functions take an
implicit this pointer.

Jeff Flinn