Specifying default parameter when calling C++ function

Question

Suppose I have code like this:

void f(int a = 0, int b = 0, int c = 0)
{
    //...Some Code...
}

As you can evidently see above with my cod

Answer 1

There isn't a reserved word for this, and f(a,,c) is not valid either. You can omit a number of rightmost optional parameters, as you show, but not the middle one like that.

http://www.learncpp.com/cpp-tutorial/77-default-parameters/

Quoting directly from the link above:

Multiple default parameters

A function can have multiple default parameters:

void printValues(int x=10, int y=20, int z=30)
{
    std::cout << "Values: " << x << " " << y << " " << z << '\n';
}

Given the following function calls:

printValues(1, 2, 3);
printValues(1, 2);
printValues(1);
printValues();

The following output is produced:

Values: 1 2 3
Values: 1 2 30
Values: 1 20 30
Values: 10 20 30

Note that it is impossible to supply a user-defined value for z without also supplying a value for x and y. This is because C++ does not support a function call syntax such as printValues(,,3). This has two major consequences:

1) All default parameters must be the rightmost parameters. The following is not allowed:

void printValue(int x=10, int y); // not allowed

2) If more than one default parameter exists, the leftmost default parameter should be the one most likely to be explicitly set by the user.