refactor into cmake project, tweak api

example/bench.cpp

@@ -0,0 +1,35 @@
+#include "tc/core.hpp"
+#include "tc/groups.hpp"
+
+#include <ctime>
+#include <vector>
+#include <iostream>
+
+int main() {
+    std::vector<tc::Group> groups = {
+        tc::group::H(2),
+        tc::group::H(3),
+        tc::group::H(4),
+        tc::group::T(100),
+        tc::group::T(500),
+        tc::group::T(1000),
+        tc::group::E(6),
+        tc::group::E(7),
+        tc::group::B(6),
+        tc::group::B(7),
+        tc::group::B(8),
+    };
+
+    for (const auto &group : groups) {
+        auto s = std::clock(); // to measure CPU time
+        auto cosets = group.solve();
+        auto e = std::clock();
+
+        double diff = (double) (e - s) / CLOCKS_PER_SEC;
+        int order = cosets.size();
+
+        std::cout << group.name << "," << order << "," << diff << std::endl;
+    }
+
+    return 0;
+}