🚀 go-pugleaf

Rich Hickey writes:

> Proposal: Reconcile Inheritance and Inlining
> --------------------------------------------
> Rich Hickey
> rich@rcs-hq.mhs.compuserve.com

> -----------------------------------------------------------------------
> I propose that the explicit keyword be allowed as a qualifier of a class 
> definition, such qualification taking the form of:

> explicit class X{
>   //the definition of X
>   };

> and that such qualification has the following meaning:

> For any class X defined as explicit -

> X cannot be derived from.

> Any calls to member functions of X, even through pointers or references 
> to X, be called with the 'normal' function mechanism, i.e.  not the 
> virtual function mechanism, as if the call took the form of 
> x-> X::function().  That is to say, all calls on X's are in the explicit 
> scope of X.  (Language lawyers please refine)

The 'normal' function mechanism can be used for any method not
declared as virtual. The only exception I can think of is when a base
class declares a virtual function you do not want to reimplement, but
you also do not want to pay for the cost of virtual invocations:

class Base {
public:
  virtual void foo();
};

inline void Base::foo() {}

class Derived : public Base {};

main() {
  Derived X;
  X.foo();
}

You can allow foo's code to be inlined by changing the declaration of
Derived to:

class Derived : public Base {
public:
  inline void foo() { Base::foo(); }
};

Since Derived::foo is not virtual, in can be inlined, as well as
Base::foo could, since it is given a scope specifier. Although this
requires some more lines of code, no changes in the standard are
required.
-- 
Alexandre Oliva
oliva@dcc.unicamp.br
Universidade Estadual de Campinas, S~ao Paulo, Brasil

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