Is there a reason that this would spit out a infinite list of zeroes?

?

Ummm... might have taken care of this already, but you need to initialize pi and pi2

while ((pi2-pi)>= tol || (pi2-pi)<=tol);

this is meant so that it runs the loop until pi2 - pi is in a certain tolerance, variable tol. For some reason it doesnt seem right but I don't know of any other way to run a loop until the difference of two numbers falls within a certain range.

What I don't understand is even if I remove the delete the cout statements from the loop, it still outputs 0 even though there is no ouptput statement. What is causing this?

I'm not in that CS 78 , but I helped somebody earlier with that assignment. For starters, you don't need that 1 in 4*(1-((pow.....stuff). If you evaluate (-1)^n / (2*n+1) at n=0 it gives you 1. The 1 is part of the approximation series.

As to why it's zero:

First time through loop:
pi = 1-(-1)^0 = 0. Anything to the zero is 1. So you have 1-1 for the numerator. 0/1 = 0; First part of your loop yields pi = 0

pi2 = 1-(-1) = 2 for numerator, 3 for denomiator, pi2=2/3

Since you #include<cmath> you can use the absolute value function. Makes the condtional statement of the do-while a little easier to read.
while(abs((pi2-pi)) >= tolerance) .........2/3-0

check conditional , 2/3 > tol, repeat loop again
2nd Time through loop:
now r=1 , n=2
pi = 0+2/3=2/3

pi2's numerator :1- (-1)^2 .....1-1 = 0, 0/5 = 0
pi2 = 2/3 + 0 = 2/3

pi2-pi = 2/3-2/3 = 0 ......This is why you're getting zeros for your answer. You keep this pattern up, you add a value, and immediately subtract it which will always give zero.

It's an infinite loop because of your conditional statement. Read it carefully. If pi2-pi > tol, repeat. OR if pi2-pi < tol, repeat. OR if pi2-pi = tol, repeat. Well, no matter what pi2-pi gives, you'll always repeat because pi2-pi will always evaluate to being greater than tol, less than tol, or equal to tol. What you meant to say was


do{
//stuff
}while(fabs(pi2-pi) >= tol);


Hope this helps clear things up some.

It's been a while since I've used abs, labs, and fabs, but make sure you use the right one. labs is for longs, fabs is for floats, but I don't remember if abs is just for ints or not.

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