March 2014 update

Task/Perfect-numbers/D/perfect-numbers-1.d

@@ -1,21 +1,12 @@
-import std.stdio, std.math, std.range, std.algorithm;
+import std.stdio, std.algorithm, std.range;
 
-bool isPerfectNumber(in int n) pure nothrow {
-    if (n < 2)
-        return false;
-
-    int sum = 1;
-    foreach (immutable i; 2 .. cast(int)sqrt(cast(real)n) + 1)
-        if (n % i == 0) {
-            immutable int q = n / i;
-            sum += i;
-            if (q > i)
-                sum += q;
-        }
-
-    return sum == n;
+bool isPerfectNumber1(in uint n) pure nothrow
+in {
+    assert(n > 0);
+} body {
+    return n == iota(1, n - 1).filter!(i => n % i == 0).sum;
 }
 
 void main() {
-    10_000.iota.filter!isPerfectNumber.writeln;
+    iota(1, 10_000).filter!isPerfectNumber1.writeln;
 }

Task/Perfect-numbers/D/perfect-numbers-2.d

@@ -1,12 +1,21 @@
-import std.stdio, std.algorithm, std.range;
+import std.stdio, std.math, std.range, std.algorithm;
 
-bool isPerfect(in uint n) pure nothrow
-in {
-    assert(n > 0);
-} body {
-    return n == reduce!((s, i) => n % i ? s : s + i)(0, iota(1, n-1));
+bool isPerfectNumber2(in int n) pure nothrow {
+    if (n < 2)
+        return false;
+
+    int total = 1;
+    foreach (immutable i; 2 .. cast(int)real(n).sqrt + 1)
+        if (n % i == 0) {
+            immutable int q = n / i;
+            total += i;
+            if (q > i)
+                total += q;
+        }
+
+    return total == n;
 }
 
 void main() {
-    iota(1, 10_000).filter!isPerfect.writeln;
+    10_000.iota.filter!isPerfectNumber2.writeln;
 }

Task/Perfect-numbers/Dart/perfect-numbers-1.dart

@@ -0,0 +1,23 @@
+/*
+ * Function to test if a number is a perfect number
+ * A number is a perfect number if it is equal to the sum of all its divisors
+ * Input: Positive integer n
+ * Output: true if n is a perfect number, false otherwise
+ */
+bool isPerfect(int n){
+    //Generate a list of integers in the range 1 to n-1 : [1, 2, ..., n-1]
+    List<int> range = new List<int>.generate(n-1, (int i) => i+1);
+
+    //Create a list that filters the divisors of n from range
+    List<int> divisors = new List.from(range.where((i) => n%i == 0));
+
+    //Sum the all the divisors
+    int sumOfDivisors = 0;
+    for (int i = 0; i < divisors.length; i++){
+        sumOfDivisors = sumOfDivisors + divisors[i];
+    }
+
+    // A number is a perfect number if it is equal to the sum of its divisors
+    // We return the test if n is equal to sumOfDivisors
+    return n == sumOfDivisors;
+}

Task/Perfect-numbers/Dart/perfect-numbers-2.dart

@@ -0,0 +1,2 @@
+isPerfect(n) =>
+    n == new List.generate(n-1, (i) => n%(i+1) == 0 ? i+1 : 0).fold(0, (p,n)=>p+n);

Task/Perfect-numbers/Dart/perfect-numbers-3.dart

@@ -0,0 +1,2 @@
+main() =>
+    new List.generate(1000,(i)=>i+1).where(isPerfect).forEach(print);

Task/Perfect-numbers/Haskell/perfect-numbers-1.hs

@@ -1 +1,2 @@
-perf n = n == sum [i | i <- [1..n-1], n `mod` i == 0]
+perfect n =
+    n == sum [i | i <- [1..n-1], n `mod` i == 0]

Task/Perfect-numbers/Ruby/perfect-numbers-1.rb

@@ -1,9 +1,7 @@
 def perf(n)
-    sum = 0
-    for i in 1...n
-        if n % i == 0
-            sum += i
-        end
-    end
-    return sum == n
+  sum = 0
+  for i in 1...n
+    sum += i  if n % i == 0
+  end
+  sum == n
 end

Task/Perfect-numbers/Ruby/perfect-numbers-2.rb

@@ -1,3 +1,3 @@
 def perf(n)
-    n == (1...n).select {|i| n % i == 0}.inject(:+)
+  n == (1...n).select {|i| n % i == 0}.inject(:+)
 end

Task/Perfect-numbers/Ruby/perfect-numbers-3.rb

@@ -0,0 +1,7 @@
+def perf(n)
+  divisors = []
+  for i in 1..Math.sqrt(n)
+    divisors << i << n/i  if n % i == 0
+  end
+  divisors.uniq.inject(:+) == 2*n
+end

Task/Perfect-numbers/Ruby/perfect-numbers-4.rb

@@ -0,0 +1,3 @@
+for n in 1..10000
+  puts n if perf(n)
+end