March 2014 update

Task/Factorial/D/factorial-1.d

@@ -0,0 +1,19 @@
+uint factorial(in uint n) pure nothrow
+in {
+    assert(n <= 12);
+} body {
+    uint result = 1;
+    foreach (immutable i; 1 .. n + 1)
+        result *= i;
+    return result;
+}
+
+// Computed and printed at compile-time.
+pragma(msg, 12.factorial);
+
+void main() {
+    import std.stdio;
+
+    // Computed and printed at run-time.
+    12.factorial.writeln;
+}

Task/Factorial/D/factorial-2.d

@@ -0,0 +1,19 @@
+uint factorial(in uint n) pure nothrow
+in {
+    assert(n <= 12);
+} body {
+    if (n == 0)
+        return 1;
+    else
+        return n * factorial(n - 1);
+}
+
+// Computed and printed at compile-time.
+pragma(msg, 12.factorial);
+
+void main() {
+    import std.stdio;
+
+    // Computed and printed at run-time.
+    12.factorial.writeln;
+}

Task/Factorial/D/factorial-3.d

@@ -0,0 +1,16 @@
+import std.stdio, std.algorithm, std.range;
+
+uint factorial(in uint n) pure nothrow
+in {
+    assert(n <= 12);
+} body {
+    return reduce!q{a * b}(1u, iota(1, n + 1));
+}
+
+// Computed and printed at compile-time.
+pragma(msg, 12.factorial);
+
+void main() {
+    // Computed and printed at run-time.
+    12.factorial.writeln;
+}

Task/Factorial/D/factorial-4.d

@@ -0,0 +1,22 @@
+uint factorial(in uint n) pure nothrow
+in {
+    assert(n <= 12);
+} body {
+    static uint inner(uint n, uint acc) pure nothrow {
+        if (n < 1)
+            return acc;
+        else
+            return inner(n - 1, acc * n);
+    }
+    return inner(n, 1);
+}
+
+// Computed and printed at compile-time.
+pragma(msg, 12.factorial);
+
+void main() {
+    import std.stdio;
+
+    // Computed and printed at run-time.
+    12.factorial.writeln;
+}

Task/Factorial/D/factorial.d

@@ -1,47 +0,0 @@
-import std.stdio, std.algorithm, std.range;
-
-/// Iterative.
-int factorial(in int n) {
-    int result = 1;
-    foreach (i; 1 .. n + 1)
-        result *= i;
-    return result;
-}
-
-/// Recursive.
-int recFactorial(in int n) {
-    if (n == 0)
-        return 1;
-    else
-        return n * recFactorial(n - 1);
-}
-
-/// Functional-style.
-int fact(in int n) {
-    return iota(1, n + 1).reduce!q{a * b};
-}
-
-/// Tail recursive (at run-time, with DMD).
-int tfactorial(in int n) {
-    static int facAux(int n, int acc) {
-        if (n < 1)
-            return acc;
-        else
-            return facAux(n - 1, acc * n);
-    }
-    return facAux(n, 1);
-}
-
-// Computed and printed at compile-time.
-pragma(msg, 15.factorial);
-pragma(msg, 15.recFactorial);
-pragma(msg, 15.fact);
-pragma(msg, 15.tfactorial);
-
-void main() {
-    // Computed and printed at run-time.
-    15.factorial.writeln;
-    15.recFactorial.writeln;
-    15.fact.writeln;
-    15.tfactorial.writeln;
-}