add outline for ule constraints, change bit to var constraints

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

src/math/polysat/var_constraint.cpp

@@ -0,0 +1,46 @@
+/*++
+Copyright (c) 2021 Microsoft Corporation
+
+Module Name:
+
+    polysat var_constraint
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2021-03-19
+    Jakob Rath 2021-04-6
+
+--*/
+
+#include "math/polysat/var_constraint.h"
+#include "math/polysat/solver.h"
+
+namespace polysat {
+
+    std::ostream& var_constraint::display(std::ostream& out) const {
+        return out << "v" << m_var << ": " << m_viable << "\n";
+    }
+
+    bool var_constraint::propagate(solver& s, pvar v) {       
+        UNREACHABLE();
+        return false;
+    }
+
+    constraint* var_constraint::resolve(solver& s, pvar v) {
+        UNREACHABLE();
+        return nullptr;
+    }
+
+    bool var_constraint::is_always_false() {
+        return false;
+    }
+
+    bool var_constraint::is_currently_false(solver& s) {
+        return s.m_viable[m_var].is_false();
+    }
+
+    void var_constraint::narrow(solver& s) {
+        s.intersect_viable(m_var, m_viable);
+    }
+
+}