Spacer engine for HORN logic

The algorithms implemented in the engine are described in the following papers

Anvesh Komuravelli, Nikolaj Bjørner, Arie Gurfinkel, Kenneth L. McMillan:
Compositional Verification of Procedural Programs using Horn Clauses over Integers and Arrays. FMCAD 2015: 89-96

Nikolaj Bjørner, Arie Gurfinkel:
Property Directed Polyhedral Abstraction. VMCAI 2015: 263-281

Anvesh Komuravelli, Arie Gurfinkel, Sagar Chaki:
SMT-Based Model Checking for Recursive Programs. CAV 2014: 17-34

src/muz/spacer/spacer_legacy_frames.h

@@ -0,0 +1,47 @@
+/**++
+  Copyright (c) 2017 Arie Gurfinkel
+
+  Legacy implementations of frames. To be removed.
+
+  Notes: this file is included from the middle of spacer_context.h
+*/
+
+class legacy_frames
+{
+    pred_transformer &m_pt;
+
+    /// level formulas
+    vector<expr_ref_vector>      m_levels;
+    /// map property to level where it occurs.
+    obj_map<expr, unsigned>      m_prop2level;
+    /// properties that are invariant.
+    expr_ref_vector              m_invariants;
+
+    void simplify_formulas (tactic& tac, expr_ref_vector& v);
+
+public:
+    legacy_frames (pred_transformer &pt) :
+    m_pt(pt), m_invariants (m_pt.get_ast_manager ()) {}
+    pred_transformer& pt () const {return m_pt;}
+    bool add_lemma (expr * lemma, unsigned level);
+    void get_frame_lemmas (unsigned level, expr_ref_vector &out)
+    {
+        if(is_infty_level(level)) { out.append(m_invariants); }
+        else if(level < m_levels.size()) { out.append(m_levels [level]); }
+    }
+
+    void get_frame_geq_lemmas (unsigned level, expr_ref_vector &out);
+    void add_frame () {m_levels.push_back (expr_ref_vector (m_pt.get_ast_manager ()));}
+
+    unsigned size () const {return m_levels.size ();}
+    unsigned lemma_size () const {return m_prop2level.size ();}
+
+
+    void propagate_to_infinity (unsigned level);
+    bool propagate_to_next_level (unsigned level);
+
+    void simplify_formulas ();
+
+    void inherit_frames (legacy_frames& other);
+
+};