Small (C/)C++ problem

[Kimm]

I am writing a small function. This function can take two arguments, and well, so far it works, the only problem I am having is that I want the secund argument to be optional. Does anyone know how I can do this??

[dcraven]

In C++ you can declare function arguments to have default values, in which case passing the value at the call is essentially optional.

For example, here are test.h and test.cc files respectively...



class TestClass
{
public:
void TestFunc (int arg1, int arg2 = 0);
};




#include <iostream>
#include "test.h"

using namespace std;

void TestClass::TestFunc (int arg1, int arg2)
{
cout << "Arg1: " << arg1 << endl;
cout << "Arg2: " << arg2 << endl;
}

int main (int argc, char** argv)
{
TestClass test;
test.TestFunc (2, 4);
test.TestFunc (4);

return 0;
}


And it's output:


Arg1: 2
Arg2: 4
Arg1: 4
Arg2: 0


You can see in the main function that the TestFunc is called twice, once with two arguments and once with only one.

HTH,
~djc

[ebrowne]

There are a couple of ways of doign this. If your using C unfortunitally you'll have to pass a "default" value if the option is not to be passed. In C++ this can be accomplised by writeing two functions with the same name just differnent number of arguments or one that passes a default like in C but the C++ handles this differently. I can never rememver if this is call overloading or polymorphism but I hope this helps.

[dcraven]

There are a couple of ways of doign this. If your using C unfortunitally you'll have to pass a "default" value if the option is not to be passed.

I didn't even know that C could do this.. I'll have to experiment.



In C++ this can be accomplised by writeing two functions with the same name just differnent number of arguments or one that passes a default like in C but the C++ handles this differently. I can never rememver if this is call overloading or polymorphism but I hope this helps.
Yes, this is another way. This would be called overloading, which sounds bad but isn't. :-)

Cheers,
~djc