add stubs for shr

src/math/polysat/shr_constraint.cpp

@@ -0,0 +1,101 @@
+/*++
+Copyright (c) 2021 Microsoft Corporation
+
+Module Name:
+
+    polysat shift right constraint.
+
+Author:
+
+    Jakob Rath, Nikolaj Bjorner (nbjorner) 2021-12-09
+
+--*/
+#pragma once
+#include "math/polysat/shr_constraint.h"
+#include "math/polysat/solver.h"
+
+namespace polysat {
+
+
+    shr_constraint::shr_constraint(constraint_manager& m, pdd const& p, pdd const& q, pdd const& r):
+        constraint(m, ckind_t::shr_t), m_p(p), m_q(q), m_r(r) {
+    }    
+
+    lbool shr_constraint::eval(pdd const& p, pdd const& q, pdd const& r) const {
+        if (p.is_val() && r.is_val()) {
+            if (p.val() >= p.manager().power_of_2())
+                return r.is_zero() ? l_true : l_false;            
+            if (r.is_val()) {
+                // todo
+            }
+            // other cases when we know lower 
+            // bound of q, e.g, q = 2^k*q1 + q2, where q2 is a constant.
+        }
+        return l_undef;
+    }
+    
+    bool shr_constraint::is_always_false(bool is_positive, pdd const& p, pdd const& q, pdd const& r) const {
+        switch (eval(p, q, r)) {
+        case l_true: return !is_positive;
+        case l_false: return is_positive;
+        default: return false;
+        }
+    }
+
+    bool shr_constraint::is_always_true(bool is_positive, pdd const& p, pdd const& q, pdd const& r) const {
+        switch (eval(p, q, r)) {
+        case l_true: return is_positive;
+        case l_false: return !is_positive;
+        default: return false;
+        }
+    }
+    
+    std::ostream& shr_constraint::display(std::ostream& out, lbool status) const {
+        switch (status) {
+        case l_true: return display(out);
+        case l_false: return display(out << "~");
+        default: return display(out << "?");
+        }
+    }
+    std::ostream& shr_constraint::display(std::ostream& out) const {
+        return out << r() << " == " << p() << " << " << q();
+    }
+    bool shr_constraint::is_always_false(bool is_positive) const {
+        return is_always_false(is_positive, p(), q(), r());
+    }
+    bool shr_constraint::is_currently_false(assignment_t const& a, bool is_positive) const {
+        return is_always_false(is_positive, p().subst_val(a), q().subst_val(a), r().subst_val(a));
+    }
+    bool shr_constraint::is_currently_true(assignment_t const& a, bool is_positive) const {
+        return is_always_true(is_positive, p().subst_val(a), q().subst_val(a), r().subst_val(a));
+    }
+
+    /**
+    * Enforce basic axioms, such as:
+    * 
+    * r = p >> q & q >= k -> r[i] = 0 for i > K - k
+    * r = p >> q & q >= K -> r = 0
+    * r = p >> q & q = k -> r[i] = p[i+k] for k + i < K
+    * r = p >> q & q >= k -> r <= 2^K-k-1
+    * 
+    * Enforce also inferences and bounds
+    * 
+    * We can assume that shr_constraint is only asserted positive.
+    */
+    void shr_constraint::narrow(solver& s, bool is_positive) {
+        SASSERT(is_positive);
+        NOT_IMPLEMENTED_YET();
+    }
+
+    unsigned shr_constraint::hash() const {
+        return mk_mix(p().hash(), q().hash(), r().hash());
+    }
+
+    bool shr_constraint::operator==(constraint const& other) const {
+        if (other.kind() != ckind_t::shr_t)
+            return false;
+        auto const& o = dynamic_cast<shr_constraint const&>(other);
+        return p() == o.p() && q() == o.q() && r() == o.r();
+    }
+
+}