initial pass at using derivatives in regex unfolding

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

src/smt/seq_regex.h

@@ -0,0 +1,77 @@
+/*++
+Copyright (c) 2011 Microsoft Corporation
+
+Module Name:
+
+    seq_regex.h
+
+Abstract:
+
+    Solver for regexes 
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2020-5-22
+
+--*/
+#pragma once
+
+#include "util/scoped_vector.h"
+#include "ast/seq_decl_plugin.h"
+#include "ast/rewriter/seq_rewriter.h"
+#include "smt/smt_context.h"
+#include "smt/seq_skolem.h"
+
+namespace smt {
+
+    class theory_seq;
+
+    class seq_regex {
+        struct s_in_re {
+            literal m_lit;
+            expr*   m_s;
+            expr*   m_re;
+            bool    m_active;
+        s_in_re(literal l, expr* s, expr* r):
+            m_lit(l), m_s(s), m_re(r), m_active(true) {}
+        };
+
+        theory_seq&      th;
+        context&         ctx;
+        ast_manager&     m;
+        vector<s_in_re> m_s_in_re;
+        scoped_vector<literal> m_to_propagate;
+
+        seq_util& u();
+        class seq_util::re& re();
+        class seq_util::str& str();
+        seq_rewriter& seq_rw();
+        seq_skolem& sk();
+
+        void rewrite(expr_ref& e);
+
+        bool propagate(literal lit);
+
+        bool coallesce_in_re(literal lit);
+
+        bool block_unfolding(literal lit, expr* s);
+
+        expr_ref mk_first(expr* r);
+
+        expr_ref unroll_non_empty(expr* r, expr_mark& seen, unsigned depth);
+
+    public:
+
+        seq_regex(theory_seq& th);
+
+        bool propagate();
+
+        void propagate_in_re(literal lit);
+
+        void propagate_is_empty(literal lit);
+        
+        void propagate_is_nonempty(expr* r);
+    };
+
+};
+