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Functions with variable-length param lists.

Started by KurtCPP Oct 10, 2003 at 4:04 AM 3 replies 1.8k views

Original Post

Oct 10, 2003 at 4:04 AM

HI everyone. Could someone explain to someone else (ie me) how I can declare a function that gets a list of parameters which size is variable (like printf() or lie a function that would calculate the average of its parameters e.g). Thanks for your help. Prog, Hex & Rock''n''Roll : I don''t like the Prog but the Prog likes me. Some nice poetry to sweeten your spirit and relax a bit before programming

original vesoljc

Oct 10, 2003 at 4:28 AM

http://search.yahoo.com/search?ei=UTF-8&fr=fp-top&p=variable+argument+list+functions+c%2B%2B

MonkeyChuff

Oct 10, 2003 at 4:33 AM

You can do it by declaring a function thus;

int Average (int iStart, ...);

So...


#include <stdarg.h>
#include <stdio.h>

int Average (int iStart, ...);

void main()
{
   printf("Average is: %d\n", Average(10,11,12,13,14,15,16,-1);
}

int Average(int iStart, ...)
{
   int i = iStart;
   int iSum = 0;
   int iCount = 0;
   va_list oArgs;

   va_start(oArgs, iStart);
   while (i != -1)
   {
      iSum += i;
      iCount++;
      i = va_arg(oArgs, int);
   }
   va_end(oArgs);

   return (iSum ? (iSum / iCount) : 0);
}

dragon___man

Nov 18, 2003 at 6:27 PM

How would you take these parameters and pass them to printf, sprintf, or fprintf?

as in:
int Average (int iStart, ...);

how would you go about doing:

int Average (int iStart, ...)
{
fprintf(someFile, I don''t know the rest
}

also, isn''t iStart supposed to be a pointer?

Paradigm Shifter

145

Paradigm Shifter

Nov 19, 2003 at 6:35 AM

Check out vsprintf for the va_args version of sprintf.

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