CODEWITHSUNDEEP
c++member-functionsdeclarenon-member-functions
RoundPi
RoundPi

Reputation: 5947

Non member function can be declared multiple times while member function can only be declared once?

Non mumber function can be delcared multiple times while member function can only be declared once? Is this right ? My example seems saying yes.

But Why ?

class Base{
public:
    int foo(int i);
    //int foo(int i=10); //error C2535: 'void Base::foo(int)' : member function already defined or declared
};

//but it seems ok to declare it multiple times
int foo(int i);
int foo(int i=10);

int foo(int i)
{
    return i;
}

int main (void)
{
    int i = foo();//i is 10 
}

Upvotes: 2

Views: 889

Answers (3)

Sarfaraz Nawaz
Sarfaraz Nawaz

Reputation: 361472

From the Standard (2003), §8.3.6/4 says,

For non-template functions, default arguments can be added in later declarations of a function in the same scope.

Example from the Standard itself:

void f(int, int);
void f(int, int = 7);

The second declaration adds default value!

Also see §8.3.6/6.

And an interesting (and somewhat related) topic:

And §9.3/2,

Except for member function definitions that appear outside of a class definition, and except for explicit specializations of member functions of class templates and member function templates (14.7) appearing outside of the class definition, a member function shall not be redeclared.

Hope that helps.

Upvotes: 6

TonyK
TonyK

Reputation: 17114

You get the same result with this simplified version:

int foo() ;
int foo() ; // OK -- extern functions may be declared more than once
class C {
  int foo() ;
  int foo() ; // Error -- member function may not be declared more than once
} ;

Perhaps the reason is historical -- lots of C code used redeclaration of extern functions, so they had to be allowed.

Upvotes: 1

Ed Heal
Ed Heal

Reputation: 60007

It certainity works - but I think it is bad practice.

Upvotes: 0

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