diff --git a/koka_bench/cpp/CMakeLists.txt b/koka_bench/cpp/CMakeLists.txt
index f587560..b4421ef 100644
--- a/koka_bench/cpp/CMakeLists.txt
+++ b/koka_bench/cpp/CMakeLists.txt
@@ -2,7 +2,7 @@ set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED YES)
 set(CMAKE_CXX_EXTENSIONS NO)
 
-foreach (source IN ITEMS rbtree.cpp)
+foreach (source IN ITEMS rbtree.cpp nqueens.cpp)
   get_filename_component(name "${source}" NAME_WE)
   set(name "cpp-${name}")
 
diff --git a/koka_bench/cpp/nqueens.cpp b/koka_bench/cpp/nqueens.cpp
new file mode 100644
index 0000000..37ab3b5
--- /dev/null
+++ b/koka_bench/cpp/nqueens.cpp
@@ -0,0 +1,94 @@
+// NQueens solution in C++
+// Note: does not free memory as that is difficult to do
+// since many subsolutions are shared
+#include <iostream>
+
+template <typename T>
+class list {
+public:
+  T head;
+  list<T>* tail;
+  list(T hd, list<T>* tl) {
+    head = hd;
+    tail = tl;
+  }
+  ~list() {
+    delete head;
+    delete tail;
+  }
+};
+
+template <typename T>
+list<T>* Cons( T hd, list<T>* tl ) {
+  return new list<T>(hd,tl);
+}
+
+template <typename T>
+int len(list<T>* xs) {
+  int n = 0;
+  while(xs != NULL) {
+    n++;
+    xs = xs->tail;
+  }
+  return n;
+}
+
+bool safe( int queen, list<int>* xs ) {
+  list<int>* cur = xs;
+  int diag = 1;
+  while(cur != NULL) {
+    int q = cur->head;
+    if (queen == q || queen == (q+diag) || queen == (q-diag)) {
+      return false;
+    }
+    diag++;
+    cur = cur->tail;
+  }
+  return true;
+}
+
+list<list<int>*>* append_safe( int k, list<int>* soln, list<list<int>*>* solns ) {
+  list<list<int>*>* acc = solns;
+  int n = k;
+  while(n > 0) {
+    if (safe(n,soln)) {
+      acc = Cons(Cons(n,soln),acc);
+    }
+    n--;
+  }
+  return acc;
+}
+
+list<list<int>*>* extend( int n, list<list<int>*>* solns ) {
+  list<list<int>*>* acc = NULL;
+  list<list<int>*>* cur = solns;
+  while(cur != NULL) {
+    list<int>* soln = cur->head;
+    acc = append_safe(n,soln,acc);
+    cur = cur->tail;
+  }
+  return acc;
+}
+
+list<list<int>*>* find_solutions( int n ) {
+  int k = 0;
+  list<list<int>*>* acc = Cons<list<int>*>(NULL,NULL);
+  while(k < n) {
+    acc = extend(n,acc);
+    k++;
+  }
+  return acc;
+}
+
+int nqueens(int n) {
+  return len(find_solutions(n));
+}
+
+int main(int argc, char ** argv) {
+    int n = 13;
+    if (argc == 2) {
+      n = atoi(argv[1]);
+    }
+    std::cout << nqueens(n) << "\n";
+    return 0;
+}
diff --git a/koka_bench/koka/CMakeLists.txt b/koka_bench/koka/CMakeLists.txt
index 495a82d..e06719f 100644
--- a/koka_bench/koka/CMakeLists.txt
+++ b/koka_bench/koka/CMakeLists.txt
@@ -1,4 +1,4 @@
-set(sources rbtree.kk)
+set(sources rbtree.kk nqueens.kk nqueens-int.kk)
 
 set(koka koka)
 
diff --git a/koka_bench/koka/nqueens-int.kk b/koka_bench/koka/nqueens-int.kk
new file mode 100644
index 0000000..8c8772e
--- /dev/null
+++ b/koka_bench/koka/nqueens-int.kk
@@ -0,0 +1,31 @@
+module nqueens-int
+import std/os/env
+
+alias solution = list<int>
+alias solutions = list<list<int>>
+
+fun safe( queen : int, diag : int, ^xs : solution ) : bool
+  match xs
+    Cons(q,qs) -> (queen != q && queen != q + diag && queen != q - diag && safe(queen,diag + 1,qs))
+    _          -> True
+
+fun append-safe( queen : int, xs : solution, xss : solutions ) : div solutions
+  if queen <= 0 then xss
+  elif safe(queen,1,xs) then append-safe( queen - 1, xs, Cons(Cons(queen,xs),xss) )
+  else append-safe( queen - 1, xs, xss )
+
+fun extend(queen : int, acc : solutions, xss : solutions ) : div solutions
+  match xss
+    Cons(xs,rest) -> extend(queen, append-safe(queen,xs,acc), rest)
+    Nil           -> acc
+
+fun find-solutions( n : int, queen : int ) : div solutions
+  if queen == 0
+   then [[]]
+   else extend(n,[], find-solutions(n,queen - 1))
+
+pub fun queens( n : int ) : div int
+  find-solutions(n,n).length
+
+pub fun main()
+  queens(get-args().head("").parse-int.default(13)).println
diff --git a/koka_bench/koka/nqueens.kk b/koka_bench/koka/nqueens.kk
new file mode 100644
index 0000000..f3fd7df
--- /dev/null
+++ b/koka_bench/koka/nqueens.kk
@@ -0,0 +1,32 @@
+module nqueens
+import std/num/int32
+import std/os/env
+
+alias solution = list<int32>
+alias solutions = list<list<int32>>
+
+fun safe( queen : int32, diag : int32, ^xs : solution ) : bool 
+  match xs
+    Cons(q,qs) -> (queen != q && queen != (q+diag) && queen != (q - diag) && safe(queen,diag.inc,qs))
+    _          -> True
+
+fun append-safe( queen : int32, xs : solution, xss : solutions ) : div solutions 
+  if queen <= 0.int32 then xss
+  elif safe(queen,1.int32,xs) then append-safe( queen.dec, xs, Cons(Cons(queen,xs),xss) )
+  else append-safe( queen.dec, xs, xss )
+
+fun extend( queen : int32, acc : solutions, xss : solutions ) : div solutions
+  match xss 
+    Cons(xs,rest) -> extend(queen, append-safe(queen,xs,acc), rest)
+    Nil           -> acc
+
+fun find-solutions( n : int32, queen : int32 ) : div solutions
+  if queen.is-zero
+   then [[]]
+   else extend(n, [], find-solutions(n,queen.dec))
+
+pub fun queens( n : int32 ) : div int
+  find-solutions(n,n).length
+
+pub fun main()
+  queens(get-args().head("").parse-int.default(13).int32).println
diff --git a/koka_bench/rbnqueens_table.md b/koka_bench/rbnqueens_table.md
new file mode 100644
index 0000000..484ffbb
--- /dev/null
+++ b/koka_bench/rbnqueens_table.md
@@ -0,0 +1,6 @@
+| Command | Mean [s] | Min [s] | Max [s] | Relative |
+|:---|---:|---:|---:|---:|
+| `build/kraken/out/bench/kraken-nqueens 10` | 2.280 ± 0.040 | 2.218 | 2.356 | 493.82 ± 56.59 |
+| `build/cpp/cpp-nqueens 10` | 0.006 ± 0.001 | 0.006 | 0.008 | 1.32 ± 0.19 |
+| `build/koka/out/bench/kk-nqueens 10` | 0.005 ± 0.001 | 0.004 | 0.006 | 1.00 |
+| `build/koka/out/bench/kk-nqueens-int 10` | 0.007 ± 0.001 | 0.006 | 0.009 | 1.46 ± 0.20 |
diff --git a/koka_bench/rbtree_table.md b/koka_bench/rbtree_table.md
index 76fc576..0cc95e4 100644
--- a/koka_bench/rbtree_table.md
+++ b/koka_bench/rbtree_table.md
@@ -1,5 +1,6 @@
 | Command | Mean [s] | Min [s] | Max [s] | Relative |
 |:---|---:|---:|---:|---:|
-| `build/kraken/out/bench/kraken-rbtree 42000` | 4.116 ± 0.030 | 4.078 | 4.160 | 862.26 ± 110.34 |
-| `build/cpp/cpp-rbtree 42000` | 0.006 ± 0.001 | 0.005 | 0.008 | 1.22 ± 0.20 |
-| `build/koka/out/bench/kk-rbtree 42000` | 0.005 ± 0.001 | 0.004 | 0.008 | 1.00 |
+| `build/kraken/out/bench/kraken-rbtree-opt 42000` | 3.814 ± 0.021 | 3.775 | 3.850 | 865.95 ± 89.32 |
+| `build/kraken/out/bench/kraken-rbtree 42000` | 4.133 ± 0.050 | 4.090 | 4.245 | 938.49 ± 97.33 |
+| `build/cpp/cpp-rbtree 42000` | 0.006 ± 0.001 | 0.005 | 0.008 | 1.30 ± 0.20 |
+| `build/koka/out/bench/kk-rbtree 42000` | 0.004 ± 0.000 | 0.004 | 0.007 | 1.00 |
diff --git a/koka_bench/test.sh b/koka_bench/test.sh
index 32ddb99..aa1e55f 100755
--- a/koka_bench/test.sh
+++ b/koka_bench/test.sh
@@ -7,7 +7,10 @@ then
 	pushd build
 	nix develop -i -c bash -c 'cmake .. -DCMAKE_BUILD_TYPE=Release && cmake --build .'
 	popd
-    rm -rf  ./build/CMakeFiles || true
 fi
+pushd build
+nix develop -i -c bash -c 'make'
+popd
 
-nix develop -i -c bash -c 'ulimit -s unlimited && find build -type f -executable -name \*rbtree -printf "\"%p 42000\"\n" | xargs hyperfine --ignore-failure --warmup 2 --export-markdown rbtree_table.md'
+nix develop -i -c bash -c 'ulimit -s unlimited && find build -type f -executable -name \*nqueens\* -printf "\"%p 10\"\n" | xargs hyperfine --ignore-failure --warmup 2 --export-markdown rbnqueens_table.md'
+nix develop -i -c bash -c 'ulimit -s unlimited && find build -type f -executable -name \*rbtree\* -printf "\"%p 42000\"\n" | xargs hyperfine --ignore-failure --warmup 2 --export-markdown rbtree_table.md'