| /* |
| * Any copyright is dedicated to the Public Domain. |
| * http://creativecommons.org/licenses/publicdomain/ |
| */ |
| |
| // Some simple testing of new, eval and some string stuff. |
| |
| // constructor -- expression array initialization |
| function ExprArray(n,v) |
| { |
| // Initializes n values to v coerced to a string. |
| for (var i = 0; i < n; i++) { |
| this[i] = "" + v; |
| } |
| } |
| |
| |
| // Print the perfect numbers up to n and the sum expression for n's divisors. |
| function perfect(n) |
| { |
| print("The perfect numbers up to " + n + " are:"); |
| var results = []; |
| |
| // We build sumOfDivisors[i] to hold a string expression for |
| // the sum of the divisors of i, excluding i itself. |
| var sumOfDivisors = new ExprArray(n+1,1); |
| for (var divisor = 2; divisor <= n; divisor++) { |
| for (var j = divisor + divisor; j <= n; j += divisor) { |
| sumOfDivisors[j] += " + " + divisor; |
| } |
| // At this point everything up to 'divisor' has its sumOfDivisors |
| // expression calculated, so we can determine whether it's perfect |
| // already by evaluating. |
| if (eval(sumOfDivisors[divisor]) == divisor) { |
| print("" + divisor + " = " + sumOfDivisors[divisor]); |
| results.push(divisor); |
| } |
| } |
| print("That's all."); |
| return results; |
| } |
| |
| |
| print("\nA number is 'perfect' if it is equal to the sum of its") |
| print("divisors (excluding itself).\n"); |
| |
| reportCompare(perfect(500).join(), "6,28,496"); |