Polysat: first pass at forbidden intervals (not yet fully integrated into solver) (#5227)

* Add interval class

* Take dependency as const reference

* Compute forbidden intervals for ule-constraints

* Add class for evaluated interval

* We need the evaluated bounds as well

* Don't add constraint to cjust multiple times (hack, to be improved later)

* typo

* More interval helpers

* Add constraint::ult factory function

* Fix forbidden interval condition

* Add solver::has_viable

* Add conflict explanation using forbidden intervals (not yet fully integrated into solver)

src/math/polysat/forbidden_intervals.h

@@ -0,0 +1,29 @@
+/*++
+Copyright (c) 2021 Microsoft Corporation
+
+Module Name:
+
+    Conflict explanation using forbidden intervals as described in
+    "Solving bitvectors with MCSAT: explanations from bits and pieces"
+    by S. Graham-Lengrand, D. Jovanovic, B. Dutertre.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2021-03-19
+    Jakob Rath 2021-04-6
+
+--*/
+#pragma once
+#include "math/polysat/constraint.h"
+#include "math/polysat/interval.h"
+#include "math/polysat/solver.h"
+
+namespace polysat {
+
+    class forbidden_intervals {
+
+    public:
+        static bool explain(solver& s, ptr_vector<constraint> const& conflict, pvar v, scoped_ptr_vector<constraint>& out_lemma);
+
+    };
+}