move headers to tc directory.

include/tc/cosets.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include "groups.h"
+#include <vector>
+
+namespace tc {
+    struct Action {
+        int coset = -1;
+        int gen = -1;
+    };
+
+    struct Cosets {
+        int ngens;
+        std::vector<int> data;
+        std::vector<Action> path;
+        int len;
+
+        explicit Cosets(int ngens);
+
+        void add_row();
+
+        void put(int coset, int gen, int target);
+
+        void put(int idx, int target);
+
+        [[nodiscard]] int get(int coset, int gen) const;
+
+        [[nodiscard]] int get(int idx) const;
+    };
+}