CODEWITHSUNDEEP
javascriptfunction
Pedro Queiroz
Pedro Queiroz

Reputation: 37

Simple function giving unexpected result

So I'm making a simple program to find the largest common divider (lcd) between two numbers, using the Euclidean Algorithm (http://www.math.jacobs-university.de/timorin/PM/continued_fractions.pdf, on the second page) it's very simple. So here's the function I've created:

        function largest_common_divider(num1, num2) {
            var remainder;
            var alpha = num1;
            var beta = num2;

            for (i = 0; i < 100; i++) { 
                /* we want to find an "n" such that
                   n * beta <= alpha < (n + 1) * beta 

                   I initiated n at 1 so that I could use n = 0 
                   as the end condition for my loop */        
                for (n = 1; n <= 0; n++) {
                    if (alpha > (n * beta)) {
                        //still didn't find the n
                    } else if (alpha == (n * beta)) {
                        //Hurray! our beta is the lcd
                        n = 0;
                        return beta;
                    } else {
                        // figure out the remainder
                        // and set n = 0 to terminate the loop
                        remainder = alpha - (n - 1) * beta;
                        n = 0;
                    }
                }
                //If we didn't find our lcd, than the previous beta
                //become the new alpha (largest number) and the
                //the remainder becomes the new beta (smaller number)
                alpha = beta;
                beta = remainder;
            }
        }

Note that, in this program I expect only positive integers and num1 > numb2 always.

So, to test this function I made this:

    var a = 45; var b = 15;

    var bloopidy = largest_common_divider(a,b);

    console.log("The largest common divider between " + a + " and " + b + " is: " + 
    bloopidy);

expecting the result to be 15, but what I got is "undefined". I used all the little knowledge I have to debug this, but I couldn't! I need help guy, any is appreciated. Thank you!!

Upvotes: 0

Views: 32

Answers (1)

melpomene
melpomene

Reputation: 85767

Your second for loop never runs:

for (n = 1; n <= 0; n++)

1 is not <= 0, so the condition is not true to begin with, so the loop never starts.

That means your code can be reduced to:

    function largest_common_divider(num1, num2) {
        var remainder;
        var alpha = num1;
        var beta = num2;

        for (i = 0; i < 100; i++) { 
            alpha = beta;
            beta = remainder;
        }
    }

This doesn't contain an explicit return, so it returns undefined implicitly.

Upvotes: 3

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