diff --git a/domains/kaar.ml b/domains/kaar.ml
new file mode 100644
index 0000000..b5eb352
--- /dev/null
+++ b/domains/kaar.ml
@@ -0,0 +1,112 @@
+let swap arr i j =
+  let tmp = arr.(i) in
+  arr.(i) <- arr.(j);
+  arr.(j) <- tmp
+
+module Matrix : sig
+  type t
+
+  val init : int -> int -> (int -> int -> Q.t) -> t
+  val copy : t -> t
+  val zero : int -> int -> t
+  val neg : t -> t
+  val add : t -> t -> t
+  val sub : t -> t -> t
+  val mul : t -> t -> t
+  val transpose : t -> t
+  val gauss : t * t -> t * t
+  val print : Format.formatter -> t -> unit
+end = struct
+  type t = { height : int; width : int; data : Q.t array array }
+
+  exception Incorrect_matrix_size
+
+  let init n m f =
+    {
+      height = n;
+      width = m;
+      data = Array.init n (fun i -> Array.init m (fun j -> f i j));
+    }
+
+  let copy m = init m.height m.width (fun i j -> m.data.(i).(j))
+  let zero n m = init n m (fun _ _ -> Q.zero)
+  let neg mat = init mat.width mat.height (fun i j -> Q.neg mat.data.(i).(j))
+
+  let add mat1 mat2 =
+    if mat1.width <> mat2.width || mat1.height <> mat2.height then
+      raise Incorrect_matrix_size
+    else
+      init mat1.height mat1.width (fun i j ->
+          Q.add mat1.data.(i).(j) mat2.data.(i).(j))
+
+  let sub mat1 mat2 = add mat1 (neg mat2)
+
+  let mul mat1 mat2 =
+    if mat1.width <> mat2.height then raise Incorrect_matrix_size
+    else
+      init mat1.height mat2.width (fun i j ->
+          List.fold_left
+            (fun sum k -> Q.add sum (Q.mul mat1.data.(i).(k) mat2.data.(k).(j)))
+            Q.zero
+            (List.init mat1.width (fun x -> x)))
+
+  let transpose mat = init mat.width mat.height (fun i j -> mat.data.(j).(i))
+
+  let gauss (m, c) =
+    let m' = copy m in
+    let c' = copy c in
+    let pivot line column =
+      let rec search_pivot l =
+        if l >= m'.height then None
+        else if not (Q.equal m'.data.(l).(column) Q.zero) then Some l
+        else search_pivot (l + 1)
+      in
+      let sub_line l sl coef =
+        for i = 0 to m'.width - 1 do
+          m'.data.(l).(i) <- Q.sub m'.data.(l).(i) (Q.mul coef m'.data.(sl).(i))
+        done;
+        for i = 0 to c'.width - 1 do
+          c'.data.(l).(i) <- Q.sub c'.data.(l).(i) (Q.mul coef c'.data.(sl).(i))
+        done
+      in
+      match search_pivot line with
+      | Some pline ->
+          swap m'.data line pline;
+          swap c'.data line pline;
+          let d = m'.data.(line).(column) in
+          for i = 0 to m'.width - 1 do
+            m'.data.(line).(i) <- Q.div m'.data.(line).(i) d
+          done;
+          for i = 0 to c'.width - 1 do
+            c'.data.(line).(i) <- Q.div c'.data.(line).(i) d
+          done;
+          if line <> m'.height - 1 then begin
+            for l = line + 1 to m'.height - 1 do
+              sub_line l line m'.data.(l).(column)
+            done;
+          end;
+          line + 1
+      | None -> line
+    in
+
+    if m'.height <> c'.height then raise Incorrect_matrix_size
+    else
+      let line = ref 0 in
+      for i = 0 to m'.width - 1 do
+        line := pivot !line i
+      done;
+      (m', c')
+
+  let print fmt mat =
+    Format.pp_print_string fmt "[";
+    Array.iter
+      (fun arr ->
+        Format.pp_print_string fmt "\n";
+        Array.iter
+          (fun elt ->
+            Format.pp_print_string fmt " ";
+            Q.pp_print fmt elt)
+          arr)
+      mat.data;
+    Format.pp_print_string fmt "\n]"
+end