write a function to add numbers to a sum?

Projects Programming
1

The code below adds all the numbers in an array to a sum, but I don't really want to use an array here. I only want a simple function that can be used to add any amount of numbers to a sum.

such as this:

 int total=add(num1, num2) 
int total=add(num1, num2, num3) 
int total=add(num1, num2, num3, num4.....)

here is my failed code:

byte love[]={1,2,3,4,5,6,8,9,10}; 


void setup() {
  Serial.begin(9600);      
}

void loop() {

  int buf= adding (love, sizeof(love));
  Serial.println(buf);
  delay(2000);  
}


int adding (byte *hate, byte len){
    int buf=0;
    for (byte i=0; i<len; i++){
    buf+= hate[i]; 
    }
  return buf;  
  }
2

In what way does it fail?

Oh, you mean it uses an array and you don't want to do that.
Hmmm. I think there is a way to specify a variable number of arguments but I forget, or never knew, how to do it :slight_smile:

Pete

3

Take a look:

4

user091ard:
Take a look:

C - Variable Arguments

http://www.cplusplus.com/reference/cstdarg/va_copy/

getting 2089 with this code. Should be 14.

#include <stdarg.h>
byte love[]={1,2,3,4,5,6,8,9,10}; 

void setup() {
  Serial.begin(9600);      
}

void loop() {

  int buf= adding (love, sizeof(love));
  Serial.println(buf);

  int buff= add (4,1,2,3,4);
  Serial.println(buff);
    
  delay(2000);  
}


int adding (byte *hate, byte len){
    int buf=0;
    for (byte i=0; i<len; i++){
    buf+= hate[i]; 
    }
  return buf;  
  }

int add (int n, ...){
  int buf=0;
  int val=n;
  int counter=0;  
  
  va_list adding, count;
  va_start (adding, n);
  
  va_copy (count, adding);
  while (val!=0){
    val=va_arg (count, int);
    ++counter;
  }
  va_end(count);
  
  for (; counter>0; counter--){
  buf+=va_arg (adding, int);
  }
  va_end(adding);
  
    return buf;
  }
5

This seems like using an H-bomb to kill an ant. Why do you want to do it this way?

1 Like
6

econjack:
This seems like using an H-bomb to kill an ant. Why do you want to do it this way?

This is the part of a library that I am writing. I need to figure out a way to do it properly in its simplest form first.

7

flyandance:
getting 2089 with this code. Should be 14.

void loop() {

int buf= adding (love, sizeof(love));
  Serial.println(buf);

int buff= add (4,1,2,3,4);
  Serial.println(buff);
   
  delay(2000); 
}

add(4, 1, 2, 3, 4) should be 1+2+3+4 = 10. The first argument is the number of arguments.

Try this solution (I don't have a board beside me, so I can't test this):

#include <stdarg.h>

int sum(int num,...)
{
   va_list valist;
   va_start(valist, num);

   int sum = 0;
   for (int i = 0; i < num; i++)
   {
      sum += va_arg(valist, int);
   }

   va_end(valist);

   return sum;
}

void setup()
{
   Serial.begin(9600);
}

void loop()
{
   int result = sum(4, 1, 1, 1, 1);
   Serial.println(result);

   delay(2000);
}
8

user091ard:
add(4, 1, 2, 3, 4) should be 1+2+3+4 = 10. The first argument is the number of arguments.

Try this solution (I don't have a board beside me, so I can't test this):

#include <stdarg.h>

int sum(int num,...)
{
  va_list valist;
  va_start(valist, num);

int sum = 0;
  for (int i = 0; i < num; i++)
  {
      sum += va_arg(valist, int);
  }

va_end(valist);

return sum;
}

void setup()
{
  Serial.begin(9600);
}

void loop()
{
  int result = sum(4, 1, 1, 1, 1);
  Serial.println(result);

delay(2000);
}

This should work, but I don't want to enter the "first argument as the number of arguments". I want every argument to be added to the sum, so sum(4, 1, 1, 1, 1) = 8, not 4;

The va_copy should do the trick, but It doesn't work for me.

9

Try this code (the only restriction is that your last argument has to be 0):

#include <stdarg.h>

int add(int num, ...)
{
	int total = num;
	int counter = 0;
	int val = num;

	va_list adding, count;
	va_start (adding, num);

	va_copy(count, adding);
	while (val != 0)
	{
		val = va_arg(count, int);
		++counter;
	}
	va_end(count);

	for (int i = 0; i < counter - 1; ++i)
	{
		total += va_arg (adding, int);
	}
	va_end(adding);

	return total;
}

void setup()
{
	Serial.begin(9600);
}

void loop()
{
	int buff = add(1, 2, 3, 4, 0);
	Serial.println(buff);
	delay(2000);
}

Or this solution (with INT_MAX):

#include <stdarg.h>
#include <limits.h>

int add(int num, ...)
{
	int total = num;
	int counter = 0;
	int val = num;

	va_list adding, count;
	va_start (adding, num);

	va_copy(count, adding);
	while (val != INT_MAX)
	{
		val = va_arg(count, int);
		++counter;
	}
	va_end(count);

	for (int i = 0; i < counter - 1; ++i)
	{
		total += va_arg (adding, int);
	}
	va_end(adding);

	return total;
}

void setup()
{
	Serial.begin(9600);
}

void loop()
{
	int buff = add(1, 2, 3, 4, 5, 1, INT_MAX);
	Serial.println(buff);
	delay(2000);
}
10

user091ard:
Try this code (the only restriction is that your last argument has to be 0):

#include <stdarg.h>

int add(int num, ...)
{
int total = num;
int counter = 0;
int val = num;

va_list adding, count;
va_start (adding, num);

va_copy(count, adding);
while (val != 0)
{
	val = va_arg(count, int);
	++counter;
}
va_end(count);

for (int i = 0; i < counter - 1; ++i)
{
	total += va_arg (adding, int);
}
va_end(adding);

return total;

}

void setup()
{
Serial.begin(9600);
}

void loop()
{
int buff = add(1, 2, 3, 4, 0);
Serial.println(buff);
delay(2000);
}




Or this solution (with INT_MAX):

#include <stdarg.h>
#include <limits.h>

int add(int num, ...)
{
int total = num;
int counter = 0;
int val = num;

va_list adding, count;
va_start (adding, num);

va_copy(count, adding);
while (val != INT_MAX)
{
	val = va_arg(count, int);
	++counter;
}
va_end(count);

for (int i = 0; i < counter - 1; ++i)
{
	total += va_arg (adding, int);
}
va_end(adding);

return total;

}

void setup()
{
Serial.begin(9600);
}

void loop()
{
int buff = add(1, 2, 3, 4, 5, 1, INT_MAX);
Serial.println(buff);
delay(2000);
}

ok, thanks a lot. so using va_copy really doesn't work. It can't exit the arguments counting while loop by itself. while for a summing function, adding a zero to the end is okay, but it really doesn't work for me here, as I am not necessarily write a summing function. I will figure it out.

11

Look up "recursive functions".

12

If you check AVR-LibC where Arduino gets its standard C libraries

http://www.nongnu.org/avr-libc/user-manual/modules.html

you may notice that there is no stdarg.h.

With more checking you can find that the AVR-LibC stdio.h does use va_list.

So just on instinct and a whim I decided to see if AVR-LibC in Arduino IDE has stdarg by default. It does.

sketch:

int x, y, z;

int addEmUp( int n, ... )
{
  x = n;
  y = 0;

  va_list vList;
  va_start( vList, n );
  
  for ( int i = 0; i < n; i++ )
  {
    z = va_arg( vList, int );
    y += z;
    Serial.println( z );
  }
  return y;
}

void setup() 
{
  Serial.begin( 250000 );
  z = addEmUp( 5, 1,2,3,4,5 );
    Serial.println();
    Serial.println( z );
}

void loop() 
{

}

output:

1
2
3
4
5

15