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help with a function

nerdpwn (18)
Need a little help with the following:
function sum4 seems to always return value 1 no matter what the input.
Also could use some advice on the code and all.
Thanks :)

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  #include<iostream.h>
#include<conio.h>
float sum1(int);
float sum2(int);
float sum3(int);
float sum4(int);
float sum1(int x)
{
 float S;
 S=(x*(x+1))/2;
 return S;
}
float sum2(int x)
{
 int i,j;
 float S=0;
 for(i=1;i<=x;i++)
 {
  for(j=1;j<=i;j++)
  S+=j;
 }
 return S;
}
float sum3(int x)
{
 int i,j;
 float S=0;
 for(i=1;i<=x;i++)
 {
  for(j=2;j<=(2*i);j+=2)
  S+=j*j;
 }
 return S;
}
float sum4(int x)
{
 int i,j;
 float S=0;
 for(i=1,j=1;i<=x;i++,j+=2)
 {
   S+=1/(j*j);
 }
 return S;
}
void main()
{
 clrscr();
 int n,x;
 float sum;
 cout<<"Welcome to Series Calculator"<<endl;
 cout<<"Enter 0 to clear console"<<endl;
 cout<<"Enter 1 to exit program"<<endl;
 cout<<"Enter 2 to calculate sum upto nth term of series 1+2+3+...+n"<<endl;
 cout<<"Enter 3 to calculate sum upto nth term of series 1+(1+2)+(1+2+3)+...+n"<<endl;
 cout<<"Enter 4 to calculate sum upto nth term of series 2^2+(2^2+4^2)+(2^2+4^2+6^2)+...+n"<<endl;
 cout<<"Enter 5 to calculate sum upto nth term of series 1/(1^2)+1/(3^2)+1/(5^2)+...+n"<<endl;
 cin>>x;
 do
 {
  switch(x)
  {
   case 0:clrscr();
	  cout<<"Conosle has been cleared successfully"<<endl;
	  cout<<"Enter another choice"<<endl;
	  cout<<"Enter 1 to exit program"<<endl;
	  cout<<"Enter 2 to calculate sum upto nth term of series 1+2+3+...+n"<<endl;
	  cout<<"Enter 3 to calculate sum upto nth term of series 1+(1+2+)+(1+2+3)+...+n"<<endl;
	  cout<<"Enter 4 to calculate sum upto nth term of series 2^2+(2^2+4^2)+(2^2+4^2+6^2)+...+n"<<endl;
	  cout<<"Enter 5 to calculate sum upto nth term of series 1/(1^2)+1/(3^2)+1/(5^2)+...+n"<<endl;
	  cin>>x;
	  while(x>5)
	  {
	   cout<<"Please enter a smaller value for choice(1 to exit)"<<endl;
	   cin>>x;
	  }
	  break;
   case 1:cout<<"Exitting from program..."<<endl;
	  cout<<"Press any key to close...";
	  x=6;
	  break;
   case 2:cout<<"Enter the number of terms upto which you want to calculate the sum of the series 1+2+3+..+n"<<endl;
	  cin>>n;
	  while(n<1)
	  {
	   cout<<"Please enter a valid number of terms"<<endl;
	   cin>>n;
	  }
	  sum=sum1(n);
	  cout<<"Sum of the series 1+2+3+..+n upto "<<n<<" terms is "<<sum<<endl;
	  cout<<"Enter another choice(1 to exit)"<<endl;
	  cin>>x;
	  while(x>5)
	  {
	   cout<<"Please enter a smaller value for choice(1 to exit)"<<endl;
	   cin>>x;
	  }
	  break;
   case 3:cout<<"Enter the number terms upto which you want to calculate the sum of the series 1+(1+2)+(1+2+3)+...+n"<<endl;
	  cin>>n;
	  while(n<1)
	  {
	   cout<<"Please enter a valid number of terms"<<endl;
	   cin>>n;
	  }
	  sum=sum2(n);
	  cout<<"Sum of the series 1+(1+2)+(1+2+3)+..+n upto "<<n<<" terms is "<<sum<<endl;
	  cout<<"Enter another choice(1 to exit)"<<endl;
	  cin>>x;
	  while(x>5)
	  {
	   cout<<"Please enter a smaller value for choice(1 to exit)"<<endl;
	   cin>>x;
	  }
	  break;
   case 4:cout<<"Enter the number terms upto which you want to calculate the sum of the series 2^2+(2^2+4^2)+(2^2+4^2+6^2)+...+n"<<endl;
	  cin>>n;
	  while(n<1)
	  {
	   cout<<"Please enter a valid number of terms"<<endl;
	   cin>>n;
	  }
	  sum=sum3(n);
	  cout<<"Sum of the series 2^2+(2^2+4^2)+(2^2+4^2+6^2)+..+n upto "<<n<<" terms is "<<sum<<endl;
	  cout<<"Enter another choice(1 to exit)"<<endl;
	  cin>>x;
	  while(x>5)
	  {
	   cout<<"Please enter a smaller value for choice(1 to exit)"<<endl;
	   cin>>x;
	  }
	  break;
   case 5:cout<<"Enter the number terms upto which you want to calculate the sum of the series 1/(1^2)+1/(3^2)+1/(5^2)+...+n"<<endl;
	  cin>>n;
	  while(n<1)
	  {
	   cout<<"Please enter a valid number of terms"<<endl;
	   cin>>n;
	  }
	  sum=sum4(n);
	  cout<<"Sum of the series 1/(1^2)+1/(3^2)+1/(5^2)+...+n upto "<<n<<" terms is "<<sum<<endl;
	  cout<<"Enter another choice(1 to exit)"<<endl;
	  cin>>x;
	  while(x>5)
	  {
	   cout<<"Please enter a smaller value for choice(1 to exit)"<<endl;
	   cin>>x;
	  }
	  break;
   default:cout<<"Invalid choice!!"<<endl;
	   cout<<"Enter another choice(1 to exit)"<<endl;
	   cin>>x;
	   while(x>5)
	   {
	    cout<<"Please enter a smaller value for choice(1 to exit)"<<endl;
	    cin>>x;
	   }
	   break;
  }
 }while(x<6);
 getch();
}
minomic (226)
Hi,
I admit I did not read all the code but the problem could be this: "j" is defined as an int, so when you do 1/(j*j) the result is an int. This means that 1/2 = 0 since the value is truncated, and the same applies for every other division. A solution could be this: (float)1/(j*j) where you are casting 1 to a float. In this way the precision of the operation is the best one among the precisions of the operands, and in this case the best precision is the floating point one.

Hope this helps.
nerdpwn (18)
Thanks for the quick reply, this has indeed fixed the problem. Do comment if you have any advise on the program overall.
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