--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/fac.cc	Wed Mar 25 15:44:15 2020 +0100
@@ -0,0 +1,18 @@
+#include <iostream>
+
+template<unsigned N>
+struct Fac {
+    static const unsigned value = N * Fac<N-1>::value;
+};
+
+template<>
+struct Fac<0> {
+    static const unsigned value = 1;
+};
+
+int main(void) {
+
+    std::cout << "3! = " << Fac<3>::value << std::endl;
+    std::cout << "10! = " << Fac<10>::value << std::endl;
+    return 0;
+}