A-M baby

Task/Factorial/D/factorial.d

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+import std.stdio, std.algorithm, std.metastrings, std.range;
+
+// iterative
+int factorial(int n) {
+    int result = 1;
+    foreach (i; 1 .. n + 1)
+        result *= i;
+    return result;
+}
+
+// recursive
+int recFactorial(int n) {
+    if (n == 0)
+        return 1;
+    else
+        return n * recFactorial(n - 1);
+}
+
+// functional-style
+int fact(int n) {
+    return iota(1, n + 1).reduce!q{a * b}();
+}
+
+// tail recursive (at run-time, with DMD)
+int tfactorial(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, toStringNow!(factorial(15)));
+pragma(msg, toStringNow!(recFactorial(15)));
+pragma(msg, toStringNow!(fact(15)));
+pragma(msg, toStringNow!(tfactorial(15)));
+
+void main() {
+    // computed and printed at run-time
+    writeln(factorial(15));
+    writeln(recFactorial(15));
+    writeln(fact(15));
+    writeln(tfactorial(15));
+}