diff --git a/include/tc/core.hpp b/include/tc/core.hpp
index d69f1b0..d2bd17f 100644
--- a/include/tc/core.hpp
+++ b/include/tc/core.hpp
@@ -6,6 +6,13 @@
 #include <string>
 
 namespace tc {
+    struct Action;
+    struct Path;
+    struct Cosets;
+    struct Rel;
+    struct Group;
+    struct SubGroup;
+
     struct Action {
         int from_idx = -1;
         int gen = -1;
@@ -18,9 +25,10 @@ namespace tc {
     };
 
     struct Path {
+        const tc::Group &context;
         std::vector<Action> path;
 
-        Path() = default;
+        explicit Path(const tc::Group &context);
 
         Path(const Path &) = default;
 
@@ -71,13 +79,14 @@ namespace tc {
     };
 
     struct Cosets {
-        int ngens;
+        const tc::Group &context;
+
         std::vector<int> data;
         Path path;
 
         Cosets(const Cosets &) = default;
 
-        explicit Cosets(int ngens);
+        explicit Cosets(const tc::Group &context);
 
         void add_row();
 
@@ -105,8 +114,6 @@ namespace tc {
         [[nodiscard]] Rel shift(int off) const;
     };
 
-    struct SubGroup;
-
     struct Group {
         const int ngens;
         std::vector<std::vector<int>> _mults;
diff --git a/src/core.cpp b/src/core.cpp
index 09ff19d..ac90397 100644
--- a/src/core.cpp
+++ b/src/core.cpp
@@ -9,6 +9,10 @@ namespace tc {
         : from_idx(from_idx), gen(gen) {
     }
 
+    Path::Path(const tc::Group &context)
+        : context(context), path() {
+    }
+
     void Path::add_row() {
         path.resize(path.size() + 1);
     }
@@ -25,18 +29,18 @@ namespace tc {
         return path.size();
     }
 
-    Cosets::Cosets(int ngens)
-        : ngens(ngens) {
+    Cosets::Cosets(const tc::Group &context)
+        : path(context), context(context), data() {
     }
 
     void Cosets::add_row() {
-        data.resize(data.size() + ngens, -1);
+        data.resize(data.size() + context.ngens, -1);
         path.add_row();
     }
 
     void Cosets::put(int coset, int gen, int target) {
-        data[coset * ngens + gen] = target;
-        data[target * ngens + gen] = coset;
+        data[coset * context.ngens + gen] = target;
+        data[target * context.ngens + gen] = coset;
 
         if (path.get(target).from_idx == -1) {
             path.put(coset, gen, target);
@@ -44,10 +48,10 @@ namespace tc {
     }
 
     void Cosets::put(int idx, int target) {
-        int coset = idx / ngens;
-        int gen = idx % ngens;
+        int coset = idx / context.ngens;
+        int gen = idx % context.ngens;
         data[idx] = target;
-        data[target * ngens + gen] = coset;
+        data[target * context.ngens + gen] = coset;
 
         if (path.get(target).from_idx == -1) {
             path.put(coset, gen, target);
@@ -55,7 +59,7 @@ namespace tc {
     }
 
     int Cosets::get(int coset, int gen) const {
-        return data[coset * ngens + gen];
+        return data[coset * context.ngens + gen];
     }
 
     int Cosets::get(int idx) const {
diff --git a/src/solve.cpp b/src/solve.cpp
index 0c144f0..10343ba 100644
--- a/src/solve.cpp
+++ b/src/solve.cpp
@@ -65,7 +65,7 @@ namespace tc {
     };
 
     Cosets Group::solve(const std::vector<int> &sub_gens) const {
-        Cosets cosets(ngens);
+        Cosets cosets(*this);
         cosets.add_row();
 
         if (ngens == 0) {