How to assign a default arguement to ofstream?
For example:

void My_Function( int a, int b = 0, ofstream outFile )
{
     //Boby of the code
}

The arguement b has a default value 0. How to assign a default
arguement to the arguement outFile so that the caller of the function
does not need to pass a value to it?

Thanks.

junw2000@gmail.com wrote:
> How to assign a default arguement to ofstream?
> For example:
> 
> void My_Function( int a, int b = 0, ofstream outFile )
> {
>      //Boby of the code
> }
> 
> The arguement b has a default value 0. How to assign a default
> arguement to the arguement outFile so that the caller of the function
> does not need to pass a value to it?
> 
> Thanks.

You can't pass streams by value.   They don't have copy constructors
but you can do it by reference.

void MyFunction (int a , int b = 0, ofstream& outFile = cout) {

....

On Jan 24, 11:42 pm, Ron Natalie <r...@spamcop.net> wrote:
> junw2...@gmail.com wrote:
> > How to assign a default arguement to ofstream?
> > For example:
>
> > void My_Function( int a, int b = 0, ofstream outFile )
> > {
> >      //Boby of the code
> > }
>
> > The arguement b has a default value 0. How to assign a default
> > arguement to the arguement outFile so that the caller of the function
> > does not need to pass a value to it?
>
> > Thanks.

>
> You can't pass streams by value.   They don't have copy constructors
> but you can do it by reference.

>
> void MyFunction (int a , int b = 0, ofstream& outFile = cout) {
>

But reference can not be reassigned. Can I pass a ofstream to
MyFunction as below?

ofstream outStream("myfile");
MyFunction ( 10, 100,outStream );

Thanks.

In message 
<9b9eb229-28ce-4c80-93d1-f13485bd810a@f47g2000hsd.googlegroups.com>, 
junw2000@gmail.com writes
>On Jan 24, 11:42 pm, Ron Natalie <r...@spamcop.net> wrote:
>> junw2...@gmail.com wrote:
>> > How to assign a default arguement to ofstream?
>> > For example:
>>
>> > void My_Function( int a, int b = 0, ofstream outFile )
>> > {
>> >      //Boby of the code
>> > }
>>
>> > The arguement b has a default value 0. How to assign a default
>> > arguement to the arguement outFile so that the caller of the function
>> > does not need to pass a value to it?
>>
>> > Thanks.
>
>>
>> You can't pass streams by value.   They don't have copy constructors
>> but you can do it by reference.
>
>>
>> void MyFunction (int a , int b = 0, ofstream& outFile = cout) {

If the function just writes to the stream and doesn't do anything 
specifically file-related, you could make it more general by using 
ostream &.
>
>But reference can not be reassigned. Can I pass a ofstream to
>MyFunction as below?

Yes. You're not reassigning it - you initialise a new reference whose 
scope is the body of the function, each time the function is called.
>
>ofstream outStream("myfile");
>MyFunction ( 10, 100,outStream );

-- 
Richard Herring