VA_NARGS.h File Reference

Declaration of the ORXONOX_VA_NARGS macro which returns the number of arguments passed to a variadic macro. More...

#include <boost/preprocessor/cat.hpp>
#include <boost/preprocessor/facilities/expand.hpp>

Go to the source code of this file.

Macros
#define	ORXONOX_VA_NARGS(...)   ORXONOX_VA_NARGS_CONCAT(__VA_ARGS__, ORXONOX_VA_NARGS_NUMBERS)
	Returns the number of arguments passed to a variadic macro. More...
#define	ORXONOX_VA_NARGS_CONCAT(...)   BOOST_PP_EXPAND(ORXONOX_VA_NARGS_INTERN(__VA_ARGS__))
#define	ORXONOX_VA_NARGS_INTERN(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11, arg12, arg13, arg14, arg15, arg16, arg17, arg18, arg19, arg20, arg21, arg22, arg23, arg24, arg25, arg26, arg27, arg28, arg29, arg30, arg31, arg32, arg33, arg34, arg35, arg36, arg37, arg38, arg39, arg40, arg41, arg42, arg43, arg44, arg45, arg46, arg47, arg48, arg49, arg50, arg51, arg52, arg53, arg54, arg55, arg56, arg57, arg58, arg59, arg60, arg61, arg62, arg63, argn, ...)   argn
#define	ORXONOX_VA_NARGS_NUMBERS

Detailed Description

Declaration of the ORXONOX_VA_NARGS macro which returns the number of arguments passed to a variadic macro.

With this utility you can overload a macro for different numbers of arguments (of course overloading is not possible for different types, as macros are not type aware, but for different numbers of arguments is still very powerful).

Important: The macro can not be overloaded for 0 arguments: ORXONOX_VA_NARGS() returns 1!

Example: A macro to call functions

myfunction();                                           // A static function
MyClass::myStaticFunction();                            // A static class function
MyClass::myFunction();                                  // A member function

#define CallFunction(...) \                             // Define a variadic macro that passes the arguments to the overloaded implementations
    BOOST_PP_EXPAND(BOOST_PP_CAT(CallFunction, ORXONOX_VA_NARGS(__VA_ARGS__))(__VA_ARGS__))

#define CallFunction1(function) \                       // Overloaded macro for 1 argument
    function()                                          // Calls the static function

#define CallFunction2(class, function) \                // Overloaded macro for 2 arguments
    class::function()                                   // Calls the static class function

#define CallFunction3(class, function, object) \        // Overloaded macro for 3 arguments
    object->class::function()                           // Calls the function on the object


CallFunction(myFunction);                               // Call the macro with 1 argument
CallFunction(MyClass, myStaticFunction);                // Call the macro with 2 arguments
CallFunction(MyClass, myFunction, new MyClass());       // Call the macro with 3 arguments

Note that the first (variadic) macro concatenates the name "CallFunction" with the number of arguments ("1" - "N"). Then all arguments are passed to the right macro.

Macro Definition Documentation

#define ORXONOX_VA_NARGS

(

...

)

ORXONOX_VA_NARGS_CONCAT(__VA_ARGS__, ORXONOX_VA_NARGS_NUMBERS)

Returns the number of arguments passed to a variadic macro.

Important: The number of arguments must be greater than zero (ORXONOX_VA_NARGS() returns 1).

#define ORXONOX_VA_NARGS_CONCAT

(

...

)

BOOST_PP_EXPAND(ORXONOX_VA_NARGS_INTERN(__VA_ARGS__))

#define ORXONOX_VA_NARGS_INTERN	(		arg1,
			arg2,
			arg3,
			arg4,
			arg5,
			arg6,
			arg7,
			arg8,
			arg9,
			arg10,
			arg11,
			arg12,
			arg13,
			arg14,
			arg15,
			arg16,
			arg17,
			arg18,
			arg19,
			arg20,
			arg21,
			arg22,
			arg23,
			arg24,
			arg25,
			arg26,
			arg27,
			arg28,
			arg29,
			arg30,
			arg31,
			arg32,
			arg33,
			arg34,
			arg35,
			arg36,
			arg37,
			arg38,
			arg39,
			arg40,
			arg41,
			arg42,
			arg43,
			arg44,
			arg45,
			arg46,
			arg47,
			arg48,
			arg49,
			arg50,
			arg51,
			arg52,
			arg53,
			arg54,
			arg55,
			arg56,
			arg57,
			arg58,
			arg59,
			arg60,
			arg61,
			arg62,
			arg63,
			argn,
			...
	)		argn

#define ORXONOX_VA_NARGS_NUMBERS

Value:

63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, \
    47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, \
    31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, \
    15, 14, 13, 12, 11, 10,  9,  8,  7,  6,  5,  4,  3,  2,  1,  0