pointer averaging function

[the b]

Does anyone know what's wrong with this function? The program that uses it runs but does not display the average. I also tried using the sum variable instead of ptr3 and had the same results.

void calculate(int days)
{
	float sum = 0;
	float average;

	temperature_node *ptr2;
	temperature_node *ptr3;
	
	ptr2 = new temperature_node;
	ptr3 = new temperature_node;
	
	current_ptr = head_ptr;
    ptr2 = current_ptr->next;


	do
	{
		ptr3->temperature = current_ptr->temperature + ptr2->temperature;
	    current_ptr = ptr2->next;
	}while(ptr2 != NULL);
	
	cout << ptr3->temperature;
	average = ptr3->temperature / days;
	cout << average;

}

[Dave Sinkula]

Does the variable in your loop condition ever change its value?

[the b]

Does the variable in your loop condition ever change its value?

yup, I changed the loop to this:

do
	{
		ptr3->temperature = current_ptr->temperature + ptr2->temperature;
	    current_ptr = ptr2->next;
		ptr2 = current_ptr->next;
	}while((current_ptr != NULL) || (ptr2 != NULL));

still doesn't work though. :(

[Dave Sinkula]

It's hard to debug incomplete code.

I put this together the other day.

#include <stdio.h>

struct node
{
   double        temperature;
   struct node  *next;
};

struct node list[] =
{
   { 90.1, &list[3] },
   { 85.6, &list[2] },
   { 87.5, &list[4] },
   { 72.9, &list[1] },
   { 80.4, NULL     },
};

int main ( void )
{
   int count = 0;
   double sum = 0;
   struct node *node;
   for ( node = list; node; node = node->next )
   {
      printf("node->temperature = %g\n", node->temperature);
      sum += node->temperature;
      ++count;
   }
   printf("average = %g\n", sum / count);
   return 0;
}

/* my output
node->temperature = 90.1
node->temperature = 72.9
node->temperature = 85.6
node->temperature = 87.5
node->temperature = 80.4
average = 83.3
*/

[the b]

It's hard to debug incomplete code.

Sorry, here is the entire program.

#include <iostream.h>

struct temperature_node
{
	int day;
	float temperature;
	temperature_node *next;
};

int day_counter = 1;

temperature_node *head_ptr;
temperature_node *current_ptr;

int get_temps(int &days, int day_entered, float &temp);
void add_temp(int days, float temp);
void move_to_end();
void show_temps();
void remove_temps();
void calculate(int &days);

int main()
{
	float temp;
	int days = 1;
	int day_entered;

	cout << "Enter the number of days you have the temperature for ";
	cin >> day_entered;

	if(get_temps(days, day_entered, temp) == 1)
	{
		head_ptr = new temperature_node;
		head_ptr->day = days;
		head_ptr->temperature = temp;
		head_ptr->next = NULL;

		while(get_temps(days, day_entered, temp) == 1)
		{
			add_temp(days, temp);
		}
		show_temps();
		calculate(days);
		remove_temps();
	}
	return 0;
}

int get_temps(int &days, int day_entered, float &temp)
{
	int keep_data = 1;

	if (day_entered < day_counter)
	{
		keep_data = 0;
	}
	else
	{
		days = day_counter;
		cout << "enter the temperature for day " << day_counter << endl;
		cin >> temp;
		day_counter++;
	}
	return(keep_data);
}


void add_temp(int days, float temp)
{
	temperature_node *rec_ptr;
	rec_ptr = new temperature_node;

	rec_ptr->day = days;
	rec_ptr->temperature = temp;
	rec_ptr->next = NULL;

	move_to_end();
	current_ptr->next = rec_ptr;
}


void move_to_end()
{
	current_ptr = head_ptr;

	while(current_ptr->next != NULL)
	{
		current_ptr = current_ptr->next;
	}
}


void show_temps()
{

	current_ptr = head_ptr;
	cout << "Day:" <<  "        " ;
	cout << "Temperature:" << endl;

	do
	{
		cout << current_ptr->day << "           ";
		cout << current_ptr->temperature << endl;
		current_ptr = current_ptr->next;
	} while (current_ptr != NULL);
}


void calculate(int &days)
{
	cout << days;
	float sum = 0;
	float average;

	temperature_node *ptr2;
	temperature_node *ptr3;
	
	ptr2 = new temperature_node;
	ptr3 = new temperature_node;
	
	current_ptr = head_ptr;
    ptr2 = current_ptr->next;

	do
	{
		ptr3->temperature = current_ptr->temperature + ptr2->temperature;
	    current_ptr = ptr2->next;
		ptr2 = current_ptr->next;
	}while((current_ptr != NULL) || (ptr2 != NULL));
	
	average = ptr3->temperature / days;
	cout << "The average temperature for " << days << "  days is: " << average << endl;
}



void remove_temps()
{
	temperature_node *temporary_ptr;

	current_ptr = head_ptr;

	do
	{
		temporary_ptr = current_ptr->next;
		delete current_ptr;
		current_ptr = temporary_ptr;
	} while (temporary_ptr != NULL);
}

[Dave Sinkula]

[disclaimer]Again, I'm a little space today.

void calculate(int &days)
{
   float average, sum = 0;
   for ( temperature_node *node = head_ptr; node; node = node->next )
   {
      sum += node->temperature;
   }
   average = sum / days;
   cout << "The average temperature for " << days
        << "  days is: " << average << endl;
}

/* my input/output
Enter the number of days you have the temperature for 5
enter the temperature for day 1
90.1
enter the temperature for day 2
72.9
enter the temperature for day 3
85.6
enter the temperature for day 4
87.5
enter the temperature for day 5
80.4
Day:        Temperature:
1           90.1
2           72.9
3           85.6
4           87.5
5           80.4
The average temperature for 5  days is: 83.3
*/

[the b]

I just fixed it now, although I did not use a for loop. I look back at the problem and I think "duh, how could I not figure it out before." Anyway here is what it looks like now

void calculate(int &days)
{
	float sum = 0;
	float average;

	current_ptr = head_ptr;

	do
	{
		sum = sum + current_ptr->temperature;
		current_ptr = current_ptr->next;
	}while(current_ptr != NULL);
	
	average = sum / days;
	cout << "The average temperature for " << days << " days is " << average << " degrees.\n";
}

Thanks alot for helping me :D