CODEWITHSUNDEEP
c++overloading
Jongsu Liam Kim
Jongsu Liam Kim

Reputation: 737

How to assign member function to member function pointer with overloading?

How can I assign member function which is overloaded to other member function (or function pointer) in C++?

My objective is to wrap member function. I have following code and it doesn't work because it has 2 "Do"s. What I want to do is wrapping Do1 or Do2 to Do with any double * or double **. Hence, I can run only Do and don't need to care about Do1 or Do2. (Maybe, I should specify condition that need to be chosen between Do1 and Do2.)

class Sample { 
    int (*Do)(double *arr);
    int (*Do)(double **arr);
    int Do1(double *arr);
    int Do1(double **arr);
    int Do2(double *arr);
    int Do2(double **arr);
};

Or do you have any suggestions for this objective?

Addition : For Thomas, function objects(functors) is a good idea, but it only resolves overloading. I want to choose function (ex, Do1 or Do2). I have several prescribed functions and I can make choose one of them to Do. However, I also want to assign custom function to Do. For example when I run Do, I could run Do1, Do2, or my own new customized function. (I should set what function will be executed when I make a instance)

and.. I can't use C++11 in my situation. (I want to, but my server has a older GCC versions)

Upvotes: 2

Views: 116

Answers (1)

Mateusz Grzejek
Mateusz Grzejek

Reputation: 12108

Your code is ill-formed and will NOT compile. You can overload function, but not objects! That is, you cannot have two pointers named 'Do' with different types. I can't recall perfectly, but MSVC would tell you something like this:

'Sample::Do' : redefinition; different basic types

If you want to do something like that, you can use flag:

class Sample
{
    int Do(double *arr);
    int Do(double **arr);
    int Do1(double *arr);
    int Do1(double **arr);
    int Do2(double *arr);
    int Do2(double **arr);

    void SetDoVersion(int version);

    int _do_version;
};

And 'Do' would look like this:

int Sample::Do(double *arr)
{
  //For more than 2-3 versions you could also use switch().
  if(this->_do_version == 1)
    return this->Do1(arr);
  else
    return this->Do2(arr);
}

int Sample::Do(double **arr)
{
  //same as above
}

SetDoVersion() sets currently 'installed' version:

void Sample::SetDoVersion(int version)
{
  this->_do_version = version;
}

This is probably the simplest solution for this task.

Upvotes: 1

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