Re: C++ in-class member initialization

From:

Victor Bazarov <v.bazarov@comcast.invalid>

Newsgroups:

comp.lang.c++

Date:

Tue, 17 May 2011 10:03:22 -0400

Message-ID:

<iqtv7b$4fs$1@dont-email.me>

On 5/17/2011 1:06 AM, Syron wrote:

Before I fell asleep last night, I had the following idea for in-class member initialization with no runtime overhead. What do you think?

#define INCLASS_INIT(ctype, name, ...) \
   class _ ## name ## _INIT { \
     private: ctype m_data; \
     public: \
       inline _ ## name ## _INIT() : \
         m_data(__VA_ARGS__) {} \
       inline _ ## name ## _INIT(const ctype& v) : \
         m_data(v) {} \
       inline operator ctype&() \
         { return m_data; } \
       inline operator const ctype&() const \
         { return m_data; } \
       inline ctype* operator&() \
         { return&m_data; } \
       inline const ctype* operator&() const \
         { return&m_data; } \
       inline ctype& operator=(const ctype& v) \
         { return m_data=v; } \
   } name

// Usage:
class Foo {
   public:
     INCLASS_INIT(int, m_v1, 1);
     INCLASS_INIT(int, m_v2, 2);
     Foo() : m_v2(3)

This is confusing. What's the value of m_v2? I see it initialized to
'3' here, but is that what I'd see when I try using it elsewhere?

{}
};

Curious (like a two-headed calf), but what's the point? Also, is it
intentionally limited to simple types? For instance, you can't declare
a reference that way, can you?

V
--
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