Pure virtual implementation, or not.

[Eibro]

VC6/VC.NET says allows implementation of pure virtual functions.
The comeau online compiler does not.
In "Effective C++" Scott Meyers provides an implementation for a pure virtual function and calls it from a derived type.

WHAT IS THE VERDICT? Does anyone have a copy of the standard to look this up in? I just had a discussion with someone about whether or not pure virtual functions could have an implementation or not. I'd REALLY love to know the answer. Thanks.

[Stoned_Coder]

yes it is allowed to provide a body for a pure virtual function. This is most commonly done with pure virtual destructors but sometimes is useful with pure virtual functions. I'm surprised the comeau compiler disallows it. It shouldnt.

[Eibro]

Update: I got the comeau compiler to compile implementation for a pure virtual function by seperating interface from implementation...

like

class a
{
   virtual void fn() = 0 { dosomething(); }
};

Won't compile but

class a
{
   virtual void fn() = 0;
};

void a::fn()
{
   dosomething();
}

Will.