diff --git a/src/math/polysat/linear_solver.h b/src/math/polysat/linear_solver.h
new file mode 100644
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+++ b/src/math/polysat/linear_solver.h
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+/*++
+Copyright (c) 2014 Microsoft Corporation
+
+Module Name:
+
+    linear_solver.h
+
+Abstract:
+
+    Fixed-precision unsigned integer linear solver
+
+    This wraps around fixplex and translates polynomials
+    into linear form.
+    Equalities, Inequalities are converted into rows and slack variables.
+    Slack variables are bounded when constraints are activated.
+    
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2021-03-19
+    Jakob Rath 2021-04-6
+
+--*/
+
+#pragma once
+
+#include "math/polysat/fixplex.h"
+#include "math/polysat/constraint.h"
+#include "math/polysat/eq_constraint.h"
+#include "math/polysat/ule_constraint.h"
+
+namespace polysat {
+
+    class linear_solver {
+        reslimit&                m_lim;
+        ptr_vector<fixplex_base> m_fix;
+        unsigned_vector          m_var2ext;
+        unsigned_vector          m_ext2var;
+        
+        //
+        // TBD trail object for 
+        // removing variables
+        // undoing variable bounds bounds
+        // removing rows from fixplex
+        //
+    public:
+        linear_solver(reslimit& lim):
+            m_lim(lim)
+        {}
+
+        void push() {}
+        void pop(unsigned n) {}
+        void internalize_constraint(constraint& c) {}
+        void set_value(pvar v, rational const& value) {}
+        void set_bound(pvar v, rational const& lo, rational const& hi) {}
+        void activate_constraint(constraint& c) {}
+
+        // check integer modular feasibility under current bounds.
+        lbool check() { return l_undef; }
+        void unsat_core(unsigned_vector& deps) {}
+
+        // current value assigned to (linear) variable according to tableau.
+        rational value(pvar v) { return rational(0); }
+    };
+
+
+
+};
+