C++ Loop Outputting Average From Set of Numbers With Decimals

[st4evr]

******See code update in one of the posts below. Any help greatly appreciated!*******

Hello,

Beginner C++ student here, first programming class. I am trying to build a program which will accept a set of numbers from the user and output the average. However, when attempting to get the average of example 1 I get 3.5. Example two I get -0. Any help is greatly appreciated!

Examples:

Output the average of the values entered.

Example 1: A run of your program might go as

1 2 3 4 blah

2.5
Example 2: A run of your program might go as

blah

no data

  #include <iostream>

using namespace std;

int main(){


  double num;
  double input;
  double sum = 0;
  double avg;

  cout << "Please enter a set of numbers. Enter a non-number to quit: "
	  << endl;
  cin >> num;

  while (cin >> num) // When value is not a number, quit.

    for(int i = 1; i <= num; i++){

      cin >> input;
      sum += input;
    }

  avg = sum / num;
  cout << "average = " << avg << endl;

return 0;

}

[LB]

What's with that for loop? Why not just scrap that and add num to sum right away? Also, you need to track how many inputs you receive.

[st4evr]

Thanks for the reply! The professor would like us to use a loop for this program, as we are learning loops right now. :0(

[LB]

You already have a while loop - are you specifically required to use a for loop? It isn't a good fit for this program.

[st4evr]

Ah, I see what you mean. I worked with the while loop and came up with the code below. However, now I get

1
Enter a number: 1
2
Enter a number: 2
3
Enter a number: 3
4
Enter a number: 4
blah

The Average is: 2.5
Press any key to continue...

I am unsure as to why I have to enter a value prior to the program returning "Enter a number: ". However, at least I am now getting the correct average. Any help with that? Thank you so much!

#include <iostream>

using namespace std;

const int numToLimit = 4;

int main(){


	double sum = 0;
	double average = 0;
	double input;

	// Get 10 numbers from the user

	//for (int i = 0; cin >> numToLimit; ++i)

	while (cin >> input) 

	{
		cout << "Enter a number: ";
		cin >> input;

		int i = 1;
		i <= numToLimit;

		sum += input;

	}

	// Get average and print it
	average = sum / numToLimit;

	cout << "The average is: " << average << endl;

	return 0;
}

[LB]

Move the output to the loop condition before the input:

while((std::cout << "Enter a number: ") && (std::cin >> input))
{

Note that this sort of thing only works for stream classes because of their ability to be implicitly converted to bool.

See also:
http://www.LB-Stuff.com/user-input

[st4evr]

Thank you so much for you help. Working code:

#include <iostream>
#include <string>
#include <cstdlib> // exit EXIT_FAILURE

using namespace std;

bool die(const string & msg);

int main(){

	int numToEnter;
	double sum = 0;
	double average = 0;
	double input;

	// Get numbers from the user

	cout << "Enter number of items: ";
	cin >> numToEnter || die("Input failure, only numbers allowed.");

	while ((cout << "Enter a number: ") && (cin >> input))

	{

		int i = 1;
		i <= numToEnter;

		sum += input;

	}

	// Get average and print it
	average = sum / numToEnter;

	cout << "The average is: " << average << endl;

	return 0;
}

bool die(const string & msg)

{
	cout << "Fatal Error: " << msg << endl;

	exit(EXIT_FAILURE);

}