[C++] Question about default parameter values

[SledgeHammer_999]

This is a question that's been bugging me for a long time. Let's say we have this function definition:


void foo(int first, int second=5, int third=555)

Then let's say I want to call it and set the 'first' and 'second' parameters, I will simply do:

foo(1, 7);

My question is what do I do if I want to change only the 'first' and 'third' parameter but leave the default value for the 'second' parameter?

[robots.jpg]

I don't think that's possible. If you find yourself needing the default value for 'second' more than the default value for 'third', switch them. Or you could take away the defaults and overload the function for two values. Otherwise you'll have to supply all three.

[lisati]

I don't think that's possible. If you find yourself needing the default value for 'second' more than the default value for 'third', switch them. Or you could take away the defaults and overload the function for two values. Otherwise you'll have to supply all three.

I agree.

My experience with C++ is minimal so I looked this up. If you omit a parameter, you have to omit all the parameters to the right.

Have a look here: http://www.learncpp.com/cpp-tutorial/77-default-parameters/

Edit:
Here's an example of using default arguments, from "Wiley's Teach Yourself C++", 7th edition



// Example program 3-6 from "Wiley's Teach Yourself C++, 7th edition

#include <iostream>

// Prototype with default arguments
void show(int = 1, float = 2.3, long = 4);

int main()
{
show(); // all three arguments default
show(5); // provide 1st argument
show(6, 7.8); // provide 1st two
show(9, 10.11, 12L); // provide all three arguments
return 0;
}

void show(int first, float second, long third)
{
std::cout << " first = " << first;
std::cout << ", second = " << second;
std::cout << ", third = " << third << std::endl;
}

[Seal Daemon]

http://www.lix.polytechnique.fr/~liberti/public/computing/prog/c/C/EXAMPLES/var_func.c - is this what you were looking for ?