Re: passing function object pointer to for_each argument

From:

Thomas Maeder <maeder@glue.ch>

Newsgroups:

comp.lang.c++.moderated

Date:

Thu, 27 Sep 2007 11:30:23 CST

Message-ID:

<m2d4w49jfw.fsf@glue.ch>

hongseok.yoon@gmail.com writes:

class test_a
{
public:
    virtual void operator()(int i)
    {
        _test();
    }

    virtual void _test()
    {
        cout << "test_a::_test()" << endl;
    }
};

class test_b : public test_a
{
public:
    virtual void _test()
    {
        cout << "test_b::_test()" << endl;
    }
};

int main()
{
    test_a* a = new test_a;
    test_a* b = new test_b;

    vector<int> v;
    v.push_back(1);

    for_each(v.begin(), v.end(), *a);
    for_each(v.begin(), v.end(), *b);

The (static) type of *b is test_a, so for_each is instantiated for the
types vector<int>::iterator and test_a. *b is passed by value, so the
copy used by for_each has (static and dynamic) type test_a.

    delete a;
    delete b;

    return 0;
}

Result :
test_a::_test()
test_a::_test()
------------------------------------------------
Why the result is not...
test_a::_test()
test_b::_test()
???

tell me why

See above.

and how can I fix it?

Change the type of b to test_b *.

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