NSInteger cannot be used twice in same multiplication

Question

I am stumped! I am using NSinteger but as all my inputs are integers and the results are therefore integers I can't see the problem that people doing division are having due to rounding.

I've looked in the developer guide for NSInteger and cannot find a warning. And my searching of this site and google hasn't yielded results.

As I state at the end I can work around it, but I feel there is something simple I am missing.

All the variables are direct, no pointers yet in the first for loop, intergerOfInterest is 0, 1, 6, 7, 4, 5, 10, 11 which is very random, I have tried swapping integerValueA^2 for the calculation but with no effect. The second for loop however gives the correct answers, 6,12,20,30,2,56,72,90

    for (loopCount = 0; loopCount < 8; loopCount++){
        integerValueA = loopCount + 2;
        integerValueB = integerValueA + 1;
        intergerOfInterest = (integerValueA) * (integerValueA);
    }


    for (loopCount = 0; loopCount < 8; loopCount++){
        integerValueA = loopCount + 2;
        integerValueB = integerValueA + 1;
        intergerOfInterest = (integerValueA) * (integerValueB);
    }

There are several loops in the structure and the common factor between the correct number and the incorrect number is if the NSInteger is used more than once in a calculation. I figure this can't be right so does anyone have an idea how I am getting this wrong. Note: if I add an extra variable to store the second instance of the number (so in the first loop I use "(integerValueA) * (integerValueB - 1 )" it works fine.

Note: Edited to use naming conventions.

Answer 1

It sounds from the discussion in the comments that your original code looked something like this:

for(int i = 0; i < 8; i++) {
    nVal = i ^ 2; // Supposed to be equivalent to nVal = i * i;
    // Do something with nVal
}

The ^ operator in C is actually the bit-wise XOR operator, not the exponent operator. The above code takes i, flips bit 1, and assigns the result to nVal.

You want to use either of the following:

// Option 1
for(int i = 0; i < 8; i++) {
    nVal = i * i;
    // Do something with nVal
}

// Option 2
for(int i = 0; i < 8; i++) {
    nVal = pow(i, 2);
    // Do something with nVal
}

Answer 2

Is it possible you have a spelling error on your variable InteRgerOfInterest instead of IntEgerOfInterest ?

GH