split definitions and declarations, move to "tc" namespace

groups.h

@@ -0,0 +1,51 @@
+#pragma once
+
+#include <vector>
+
+struct Cosets {
+    int ngens;
+    std::vector<int> data;
+    int len;
+
+    Cosets(int ngens, const std::vector<int> &data);
+
+    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;
+};
+
+struct Mult {
+    int gen0, gen1, mult;
+};
+
+struct RelTable {
+    int gens[2]{};
+    int mult;
+    std::vector<int *> lst_ptr;
+    std::vector<int> gen;
+
+    explicit RelTable(Mult m);
+
+    int add_row();
+};
+
+struct Group {
+    int ngens;
+    std::vector<std::vector<int>> _mults;
+
+    explicit Group(int ngens, const std::vector<Mult> &rels = {});
+
+    void setmult(Mult m);
+
+    [[nodiscard]] std::vector<Mult> get_mults() const;
+
+    [[nodiscard]] Group product(const Group &other) const;
+
+    [[nodiscard]] Group power(int p) const;
+};