adding nra solver

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

src/util/lp/lar_solver.cpp

@@ -1387,8 +1387,14 @@ void lar_solver::shrink_explanation_to_minimum(vector<std::pair<mpq, constraint_
     lean_assert(this->explanation_is_correct(explanation));
 }
 
-final_check_status check_int_feasibility() {
+final_check_status lar_solver::check_int_feasibility() {
-	return final_check_status::GIVEUP;
+    unsigned n = A_r().column_count();
+    for (unsigned j = 0; j < n; j++) {
+        if (column_is_integer(j) && column_value_is_integer(j))
+            continue;
+        return final_check_status::GIVEUP;
+    }
+	return final_check_status::DONE;
 }
 } // namespace lean
 

src/util/lp/lar_solver.h

@@ -406,6 +406,16 @@ public:
         unsigned ext_var = m_columns_to_ext_vars_or_term_indices[j];
         return m_ext_vars_to_columns.find(ext_var)->second.is_integer();
     }
+
+    static bool impq_is_int(const impq& v) {
+        return v.x.is_int() && is_zero(v.y);
+    }
+    
+    inline
+    bool column_value_is_integer(unsigned j) const {
+        const impq & v = m_mpq_lar_core_solver.m_r_x[j];
+        return impq_is_int(v);
+    }
     inline bool column_is_real(unsigned j) const { return !column_is_integer(j); }	
 	final_check_status check_int_feasibility();
 };

src/util/lp/nra_solver.h

@@ -42,6 +42,5 @@ namespace nra {
         void push();
         
         void pop(unsigned n);
-        
     };
 }