asked on

variable argument list

Hello

I want my function to take in a varialbe number of arguments,
so for example if i had just one argument I would call it by
function(1, arg1)

or if I had 2 arguments then I'd call
function(2, arg1, arg2)

or 3 then
function(3, arg1, arg2, arg3)
etc...

so I would have to have something like a switch statement to handle these variable cases

but what if I could possibly have 200 arguments
then how would I handle this?

i.e., how would I have a variable arugment list that doesnt require knowing the number of arguments in case the number of arguments could be from 1 to a million!

thanks..

lost_bits1110

ASKER

or if someone could let me know if its possible at all...
Thanks

jkr

There are a few ways using 'va_arg', e.g.

/* VA.C: The program below illustrates passing a variable
* number of arguments using the following macros:
* va_start va_arg va_end
* va_list va_dcl (UNIX only)
*/

#include <stdio.h>
#define ANSI /* Comment out for UNIX version */
#ifdef ANSI /* ANSI compatible version */
#include <stdarg.h>
int average( int first, ... );
#else /* UNIX compatible version */
#include <varargs.h>
int average( va_list );
#endif

void main( void )
{
/* Call with 3 integers (-1 is used as terminator). */
printf( "Average is: %d\n", average( 2, 3, 4, -1 ) );

/* Call with 4 integers. */
printf( "Average is: %d\n", average( 5, 7, 9, 11, -1 ) );

/* Call with just -1 terminator. */
printf( "Average is: %d\n", average( -1 ) );
}

/* Returns the average of a variable list of integers. */
#ifdef ANSI /* ANSI compatible version */
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 );
}
#else /* UNIX compatible version must use old-style definition. */
int average( va_alist )
va_dcl
{
int i, count, sum;
va_list marker;

va_start( marker ); /* Initialize variable arguments. */
for( sum = count = 0; (i = va_arg( marker, int)) != -1; count++ )
sum += i;
va_end( marker ); /* Reset variable arguments. */
return( sum ? (sum / count) : 0 );
}
#endif

lost_bits1110

ASKER

Okay, but how in my code could I make your following statement

printf( "Average is: %d\n", average( 2, 3, 4, -1 ) )

more general?

because what if I have say 200 arguments then I would have to do

if (numArgs == 1)
printf( "Average is: %d\n", average( 1,1) );
if (numArgs == 2)
printf( "Average is: %d\n", average( 2, 1, 2 ) );
....etc....
if (numArgs == 200)
printf( "Average is: %d\n", average( 200, 3, 4, -1, etc.............. ) );

jkr

You mean you want to arrange/create the arguments at runtime?

lost_bits1110

ASKER

yes precisely......

ASKER CERTIFIED SOLUTION

jkr

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lost_bits1110

ASKER

okay, even if the arguments i'm passing are arrays?