I'm getting possible loss of data error in my visual studio 2013 professional

Question

1.00/5 (1 vote)

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C++

#include<string.h>
#include <iostream>
using namespace std;
class Average{

private:
	void sumFn(int);
	int userValue, sum;
	float avg;

public:
	Average();
	~Average();
	float printAvg();
	void inputVal(int);
};

Average::Average()
{
	/* 
	int uVal[4];
	for (int i = 0; i < 5; i++)
	userValues[i] =  uVal[i] = 00; */
	
	sum = 0;
	userValue = 0;
	avg = 0.0;
}

void Average:: sumFn(int ss){
	sum += ss;
}

Average::~Average()
{
	cout << "***  \nThank you for using Average Software!  ***";
	cout << "\n*** Have a Nice Day  ***!";
}

void Average::inputVal(/* int uVal[4]*/ int uu)
{
	/*for (int i = 0; i < 5; i++){
		userValues[i] = uVal[i];
	}*/
	sumFn(uu);
}

float Average::printAvg()
{
	/*for (int i = 0; i <= 5; i++)

		return (userValues[i]); */
		
	return (avg = (sum/4));
}

int main()
{
	//int v1[4] = 0;
	int v2 = 0;
	//Average av[2]
		Average a2;
	//int uVal[4];

		//a2.~Average();
	
	for (int i = 0; i < 4; i++)
	{
		cout << "\nEnter marks of subject: " << i <<" : ";
		cin >> v2;
		//av[i].inputVal(v2);
		a2.inputVal(v2);

	}// end of for loop

	/* 
	a1.inputVal(v1, v2);
	cout << "\nThe Quotient is:" << d1.printQuote();*/

	cout << "\nThe Average is: " << a2.printAvg()<<endl;
	
	system("pause");

}// end of main

[Edit by Jochen Arndt: Added code block and removed empty lines]

Posted 13-May-15 2:32am

DieHardCoder

Updated 13-May-15 2:44am

Jochen Arndt

v2

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Comments

Richard MacCutchan 13-May-15 9:07am

Firstly, please remove all the comment lines that have nothing to do with the problem. And secondly, show us exactly where the error occurs.

2 solutions

Solution 1

This is because you are using the single precision float type. To avoid the error, change all variables, operations and return values to double or cast values.

In your code the error occurs when performing operations with integer arguments that must be converted to float. Integers can represent numbers with more digits than can be hold by single precision floating values. The max. 32-bit signed integer value INT_MAX is 2147483647 which has ten decimal digits. But the mantissa of single precision floating values has only 24 bits (can only hold 6 decimal digits, see definition of FLT_DIG and FLT_MANT_DIG in float.h). So some digits may get loss when converting large integer values to float.

Posted 13-May-15 3:06am

Jochen Arndt

Comments

Sergey Alexandrovich Kryukov 13-May-15 10:30am

5ed.
—SA

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CPallini · Accepted Answer · 2015-05-13T03:16:00

You are possibly loosing some decimals. Change from

Quote:
return (avg = (sum/4));

to

C++

return (avg = ((float)sum/4));

It is worthy noting your code could be more concise, e.g.

C++

#include <iostream>
using namespace std;


class Average
{
  int sum, items;
public:
  Average():sum(0), items(0){}
  void add(int v){ sum += v; ++items; }
  double avg()
  {
    if (items==0) throw("sorry, no items");
    return (double)sum/items;
  }
};

int main()
{
  int marks;
  Average a;

  while (true)
  {
    cout << "plaese input marks (-1 to stop): " << endl;
    cin >> marks;
    if ( marks < 0) break;
    a.add(marks);
  };
  try
  {
    cout << "the average is " << a.avg() << endl;
  }
  catch( const char * msg )
  {
    cout << msg << endl;
  }
}