Should you write "public virtual" or "virtual public" in virtual inheritance?

Question

Based on http://en.wikipedia.org/wiki/Virtual_inheritance

class Animal 
{
...
};

// Two classes virtually inheriting Animal:
class Mammal : public virtual Animal 
{
...
};

I also saw books use the following syntax,

class Mammal : virtual public Animal 
{
...
};

Question> Which is one the C++ standard?

Thank you

FYI this isn't multiple inheritance, this is virtual inheritance that you're asking about. — Adam Rosenfield, Mar 29 '11 at 02:44
@Adam, we should use virtual inheritance from the base class when we use multiple inheritance. — q0987, Mar 29 '11 at 02:52

score 16 · Accepted Answer · answered Mar 29 '11 at 02:28

16

From ISO/IEC 14882:2003(E) - 10.1

A list of base classes can be specified in a class definition using the notation:

base-clause:
    : base-specifier-list

base-specifier-list:
    base-specifier
    base-specifier-list , base-specifier

base-specifier:
    ::opt nested-name-specifieropt class-name
    virtual access-specifier opt ::opt nested-name-specifieropt class-name
    access-specifier virtual opt ::opt nested-name-specifieropt class-name

access-specifier:
    private
    protected
    public

Notice that either is recommended.

answered Mar 29 '11 at 02:28

Mahesh

34,573
20
89
115

@q0987 - Google search on mentioned standard name, you should be able to find one :) – Mahesh Mar 29 '11 at 03:23
1

this is the grammar, but what of the semantics, ie is the meaning equivalent ? – Matthieu M. Mar 29 '11 at 06:54

score 4 · Answer 2 · answered Mar 29 '11 at 08:19

4

Both are standard. Use whichever the local coding conventions require.

answered Mar 29 '11 at 08:19

James Kanze

150,581
18
184
329

Should you write "public virtual" or "virtual public" in virtual inheritance?

2 Answers2

Linked