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javaloopsbessel-functions

Multiplying and Dividing by Two

Why are these two snippets of code giving two different results?

    double sum = 1.0;
    double xSqFour = x * x / 4;

    for (int i = 48; i > 1; i-=2) {
        sum = 1.0 + (xSqFour / ((i/2) * (i/2))) * sum;
    }

    return sum;

and

    double sum = 1.0;
    double xSqFour = x * x / 4;

    for (int i = 24; i > 1; i--) {
        sum = 1.0 + (xSqFour / (i * i)) * sum;
    }

    return sum;
Solution

  • You have a bounds error on your second loop. It should be i > 0. The first loop has i > 1, but it also divides i by 2. 1 / 2 == 0, so it should be i > 0 in the second loop.