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Variable length parameter lists

General and Gameplay Programming Programming

Started by granat March 09, 2001 11:56 PM

1 comment, last by granat 23 years, 11 months ago

granat

Author

122

March 09, 2001 11:56 PM

I know how to declare: MyFunc(int a, ...) If I called this function like this: int x=10; int y=8; MyFunc(x, y); How can I obtain the value for y inside the function?

-------------Ban KalvinB !

Quantum

122

March 10, 2001 01:05 AM

An example from the MSDN:

  int average( int first, ... ){   int count = 0, sum = 0, i = first;   va_list marker;   va_start( marker, first );     /* Initialize variable arguments. */   while( i != -1 )   {      sum += i;      count++;      i = va_arg( marker, int);   }   va_end( marker );              /* Reset variable arguments.      */   return( sum ? (sum / count) : 0 );}

Basically, make a va_list, call va_start and pass it the list name and the name of the variable(in your case ''a''), and then call va_arg until it returns -1. Then call va_end to finish up.

LilBudyWizer

491

March 10, 2001 02:40 PM

Worth noting is that it returns -1 because that is the last parameter passed, i.e. Average(1,2,3,4,-1). You also have to be able to determine the type of the arguements. With printf that is done by the format string.

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Variable length parameter lists

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