Default argument for 'bool&' in function declaration

Question

If I have a function declaration as follows:

int Remove(Object *spl, Object1* parent,
           int num, Object2* th = NULL, bool& proceed
          );

I get an error that I need to declare 'proceed' becasue 'th' has a default argument. I understand why. But how do I make a default argument for a "bool&" in function declaration?

http://stackoverflow.com/questions/2816293/passing-optional-parameter-by-reference-in-c — Bryan Chen, Mar 16 '16 at 22:02
Swap the order. Put the defaults to the end of the signature — Ed Heal, Mar 16 '16 at 22:03
@Poriferous I think you are confusing `bool` objects with bit-fields. You cannot have references to bit-fields, but a `bool` is at least as big as a `char`. — Brian Bi, Mar 16 '16 at 22:08

IceFire · Answer 1 · 2016-03-16T22:14:08.190

1

All function in C++ have to end with the default arguments. It is not possible to call your function like so:

Remove(someSpl, someParent, 10, /* no argument, use default */, someBool);

Since you cannot omit arguments in the middle, they have to wander to the end.

Regarding the first comment clarifying the question, let me give a small example that should transfer fine to your application:

void changingBoolFunction(bool& someBool)
{
    someBool = false;
}

bool changeableBool = true;
changingBoolFunction(someBool);
cout << (changeableBool ? "true" : "false"); // output: false

edited Mar 16 '16 at 22:14

answered Mar 16 '16 at 22:07

IceFire

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I understand that. Let me rephrase my question. How do I initialise 'bool&' in: int Remove(Object *spl, Object1* parent, bool& proceed, int num = 0, Object2* th = NULL ); – ssn Mar 16 '16 at 22:11

score 1 · Answer 2 · answered Mar 16 '16 at 22:14

To clarify: that value for th is a default argument, not an initialization. And once you've put in a default argument every argument after that one has to have a default. It's unusual to have a default value for an argument that's passed by (modifiable) reference, but if that's what you really want, you have to provide a bool object for that default argument:

bool bool_value = true;
int Remove(Object *spl, Object1* parent,
           int num, Object2* th = NULL, bool& proceed = bool_value
          );

After the function returns, if it changed the value of proceed that change will show up in bool_value.

Default argument for 'bool&' in function declaration

2 Answers2