Re: Can I use overloading for optional parameters?

From:
DeMarcus <use_my_alias_here@hotmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Wed, 31 Mar 2010 09:43:37 CST
Message-ID:
<4bb34d1a$0$281$14726298@news.sunsite.dk>
Goran wrote:

On Mar 30, 5:49 pm, DeMarcus <use_my_alias_h...@hotmail.com> wrote:

Hi,

I need to provide a set of parameters to a function where one or more
can be optional. Standard C++ can only provide default values for the
last parameters and a default value representing N/A for references is
not quite pleasant.

I came up with an idea of overloading the optional parameters. Please
give me your feedback.

class SomeClass
{
public:

    void fnc( int& a );
    void fnc( int& a, int& b );
    void fnc( int& a, int& b, int& c );

    // Now insert a pointer if we want to disable (b).
    void fnc( int& a, int* b, int& c );

};


 From what I gather, you have b and c as optional parameters from the
get-go. So I would go for:

void fnc( int& a, int* b=NULL, int* c=NULL);

That gives you, the implementor, all the information you need, and
only one public interface to maintain. That also gives you, the
user :-), a possibility to call any possible variant (a, ab, ac, abc)
through only one interface point, but with the inconvenience (IMO, a
very small one) of having to type a "&" in front of optional
parameters.

Goran.


Yes, in most cases that's the way to go, but in a few cases with
temporaries, that solution gives compiler warnings. E.g.

fnc( &TmpClass( "Hello" ), NULL, &TmpClass( "World" ) );

"Warning, taking address of temporary"

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