C++ Template Metaprogramming Game
Templates in C++ are a useful feature. Without them you’d not have template functions, or more usefully template classes like vector etc. But there is an even more useful feature called template metaprogramming. It’s a very advanced and clever feature; one I have never done and I don’t think anyone could say they’ve mastered C++ unless they are good at it.
Here’s an example of the simplest example I could find. It comes from here and what it does is generate factorials of numbers at compile time. So when you run it it comes back with the answer immediately.
// factorial.cpp
#include <iostream>
template <int N> // (2)
struct Factorial{
static int const value = N * Factorial<N-1>::value;
};
template <> // (3)
struct Factorial<1>{
static int const value = 1;
};
int main(){
std::cout << std::endl;
std::cout << "Factorial<5>::value: " << Factorial<5>::value << std::endl; // (1)
std::cout << "Factorial<10>::value: " << Factorial<10>::value << std::endl;
std::cout << std::endl;
}But if you think that is clever how about a game where every time you compile it, it makes a move and remembers the move between turns? A developer called Matt Bierner has developed a snake game using template metaprogramming.
So I downloaded it into my Ubuntu, installed Clang and clang tool just for good measure and compiled. This is the output. Iv’e snipped a lot out after the first two. Ot’s very clever, in this case, not much use but I doubt if there is any other programming language in which you could do this. The compile plays the game, running it just outputs the results. Yes it’s not exactly practical but still…
david@davidvm:~/STT-C-Compile-Time-Snake-master/stt-snake$ clang++ -std=c++1y main.cpp -o snake ; ./snake ------------------ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺▶*╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ------------------ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺*╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺▶▶╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ .... -- You Are Dead -- ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ *╺╺╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺ ╺▼╺╺╺╺╺╺╺╺ ╺█▲╺╺╺╺╺╺╺ ╺▼▶╺╺╺╺╺╺╺ ╺╺╺╺╺╺╺╺╺╺
Sometimes I walk up around 3:00 AM and my mind is abuzz with things like this. Last night was one such night. The first thought was I should stop calling it a Roguelike. There’s a certain set of conventions with those and I don’t want to be limited by that.
It’s not really a thing done in C, although you could do. I came across 
The original rogue used graphics. This was back in the era of terminals and home computers and graphics could be quite limited. So there’s a tradition of using text. However if you do a google image search for rogue game like I did here, you can see that while many of them are text there are a couple that are graphics.
If you are looking for inspiration for games creation, take a look at 
The internet archive (yes them again!) not only has archives of most things I’ve done, but they also 
This is a 4x game (Explore, Expand, Exploit, Exterminate) . “Select from one of seven races – or craft your own – to explore dozens, hundreds, or even thousands of systems in a galaxy of your choosing. Expand across unique and varied planets and ultimately exterminate – or subjugate – any who stand in your way either in offline single player or up to 28 player multiplayer.” as gog.com put it.
