RE: the sizeof "internal class" ... a question to C++ gurus

From: Philippe Canal <pcanal_at_fnal.gov>
Date: Fri, 21 Jan 2005 08:42:21 -0600

Hi Jacek,

> None of them has the "value_type" implemented, though ...

You should not need it for those ... I must be confused on what you are trying to do.

Anyway if you really need to you can specialize you template:

template <class T> class MyTemplate {

   // generic version with assume that T is also a template    typedef T value_type;
   ... Use sizeof(value_type) and sizeof(value_type::value_type); }

// specialization
Template <class T> class MyTemplate <complex<T> > {

   // semi-generic version for complex
   typedef complex<T> value_type;
    ... Use sizeof(value_type) and sizeof(T) ... }

Cheers,
Philippe.

-----Original Message-----
From: owner-roottalk_at_pcroot.cern.ch [mailto:owner-roottalk_at_pcroot.cern.ch] On Behalf Of Jacek M. Holeczek
Sent: Friday, January 21, 2005 2:32 AM
To: RootTalk
Subject: RE: [ROOT] the sizeof "internal class" ... a question to C++ gurus

Hi,

> template <class T> MyTemplate {
> public:
> typedef T value_type;
> };

>


> Then you can do

> 	sizeof(MyTemplate<MyClass>::value_type)


Nice trick, indeed.

However, I need this to work with basic types like "float", "double", "complex<float>", "complex<double>", ... None of them has the "value_type" implemented, though ...

Any other ideas?
Thanks in advance,
Best regards,
Jacek. Received on Fri Jan 21 2005 - 16:18:50 MET