// at compile time, split a number into figures /* Algorithm n = input a = [] while(n < 10) a.append(n % 10) n /= 10 a.append(n) */ #include using namespace std; // Type class, helper for ::type template struct Type{ using type = T; }; // --- If class on type // declaration template struct IfType; // specialisation with B == true so type == T template struct IfType : Type {}; // specialisation with B == false so type == V template struct IfType : Type {}; // Helper to call IfType<...>::type easily template using If_t = typename IfType::type; // --- Result class // declaration template struct Result; // "recursion" step, print an integer then call show of the parent class template struct Result : Result{ static void show(){ cout << J << ' '; Result::show(); } }; // "recursion stop", print the integer template struct Result{ static void show(){ cout << I << endl; } }; // --- Array class, helper that "store" our integers template struct Array{}; // --- Split class // declaration template struct SplitImpl; // helper to call SplitImpl> easily template using Split = SplitImpl>; // first step, if I < 10, we stop, else we keep I%10 and go on with I/10 template struct SplitImpl> : If_t< (I < 10), Result, SplitImpl, Array> > {}; // generic step, if I < 10, we stop, else we keep I%10 and go on with I/10 template struct SplitImpl, Array...> : If_t< (I < 10), Result, SplitImpl, Array, Array...> > {}; // --- Test Display class template struct TestDisplay{ static void run(){ cout << "Value to be split: " << I << endl; cout << "Result:" << endl << " "; Split::show(); cout << endl; } }; int main() { TestDisplay<124>::run(); TestDisplay<42>::run(); TestDisplay<0>::run(); TestDisplay<10000>::run(); return 0; }

compile time number split