Practical numbers: Difference between revisions

=={{header|Wren}}==

{{libheader|Wren-math}}

<lang ecmascript>import "/math" for Int, Nums

var powerset // recursive

powerset = Fn.new { |set|

if (set.count == 0) return [[]]

var head = set[0]

var tail = set[1..-1]

return powerset.call(tail) + powerset.call(tail).map { |s| [head] + s }

}

var isPractical = Fn.new { |n|

if (n == 1) return true

var divs = Int.properDivisors(n)

var subsets = powerset.call(divs)

var found = List.filled(n, false)

var count = 0

for (subset in subsets) {

var sum = Nums.sum(subset)

if (sum > 0 && sum < n && !found[sum]) {

found[sum] = true

count = count + 1

if (count == n - 1) return true

}

}

return false

}

System.print("In the range 1..333, there are:")

var count = 0

var practical = []

for (i in 1..333) {

if (isPractical.call(i)) {

count = count + 1

practical.add(i)

}

}

System.print(" %(count) practical numbers")

System.print(" The first ten are %(practical[0..9])")

System.print(" The final ten are %(practical[-10..-1])")

System.print("\n666 is practical: %(isPractical.call(666))")</lang>

{{out}}

<pre>

In the range 1..333, there are:

77 practical numbers

The first ten are [1, 2, 4, 6, 8, 12, 16, 18, 20, 24]

The final ten are [288, 294, 300, 304, 306, 308, 312, 320, 324, 330]

666 is practical: true

</pre>