separate int-cube functionalty

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/math/lp/int_cube.h

@@ -0,0 +1,41 @@
+/*++
+Copyright (c) 2020 Microsoft Corporation
+
+Module Name:
+
+    int_cube.h
+
+Abstract:
+
+    Cube finder
+
+    This routine attempts to find a feasible integer solution
+    by tightnening bounds and running an LRA solver on the 
+    tighter system.
+
+Author:
+    Nikolaj Bjorner (nbjorner)
+    Lev Nachmanson (levnach)
+
+Revision History:
+--*/
+#pragma once
+
+#include "math/lp/lia_move.h"
+
+namespace lp {
+    class int_solver;
+    class lar_solver;
+    class int_cube {
+        class int_solver& lia;
+        class lar_solver& lra;
+        bool tighten_term_for_cube(unsigned i);
+        bool tighten_terms_for_cube();
+        void find_feasible_solution();
+        impq get_cube_delta_for_term(const lar_term& t) const;
+    public:
+        int_cube(int_solver& lia);
+        ~int_cube() {}
+        lia_move operator()();
+    };
+}