blob: ceb340d7a7415fa96be21017a7cd3662d76f3893 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
|
/*
* 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");
|
