How to declare and use a variadic method?

[Rui Maciel]

Does anyone knows how to declare variadic methods so that they can be used to emulate printf? If
so, can you please post a small example describing how it's done?


Thanks in advance,
Rui Maciel

 

[Victor Bazarov]

Does anyone knows how to declare variadic methods so that they can be used to emulate printf? If
so, can you please post a small example describing how it's done?

http://en.wikipedia.org/wiki/Stdarg.h

V

 

[James Kanze]

On 9/27/2010 10:51 AM, Rui Maciel wrote:

http://en.wikipedia.org/wiki/Stdarg.h

That's for C; it doesn't treat the issues which come up in C++.

For C++, the answer is simply, you don't. You can only pass
PODs as varargs, which makes it pretty useless in C++.

 

[Gert-Jan de Vos]

Does anyone knows how to declare variadic methods so that they can be used to emulate printf?  If
so, can you please post a small example describing how it's done?

C++0x adds variadic function templates. This allows variadic
functions with proper C++ typesafe arguments. There is even a
printf() example in wikipedia:

http://en.wikipedia.org/wiki/C++0x#Variadic_templates

 

[Juha Nieminen]

That's for C; it doesn't treat the issues which come up in C++.

For C++, the answer is simply, you don't. You can only pass
PODs as varargs, which makes it pretty useless in C++.

Well, he wanted to emulate printf, and printf only supports primitive
types, so there's no problem.

If he wants to support other types, then he should use the same
approach as the C++ streams use.

 

[James Kanze]

Well, he wanted to emulate printf, and printf only supports
primitive types, so there's no problem.

Except all of the problems that printf has.

If he wants to support other types, then he should use the
same approach as the C++ streams use.

Perhaps.

One can argue about the choice of the % operator (horrible), but
boost::format supports printf like formatting with a variable
number of arguments (but in a typesafe way); many years ago, so
did my GB_Format (using a completely different technique than
boost::format).