working on named assertions support

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/solver/solver_na2as.cpp

@@ -0,0 +1,96 @@
+/*++
+Copyright (c) 2012 Microsoft Corporation
+
+Module Name:
+
+    solver_na2as.cpp
+
+Abstract:
+
+    Solver that implements "named" assertions using assumptions (aka answer literals).
+    That is, a named assertion assert_expr(t, a) is mapped into
+          a implies t
+    and 'a' is used as an extra assumption for check_sat.
+
+Author:
+
+    Leonardo (leonardo) 2012-11-02
+
+Notes:
+
+--*/
+#include"solver_na2as.h"
+
+solver_na2as::solver_na2as() {
+    m_manager = 0;
+}
+
+solver_na2as::~solver_na2as() {
+    reset();
+}
+
+void solver_na2as::assert_expr(expr * t, expr * a) {
+    SASSERT(m_manager != 0);
+    expr * new_t = m_manager->mk_implies(a, t);
+    m_manager->inc_ref(a);
+    m_assumptions.push_back(a);
+    assert_expr(new_t);
+}
+    
+void solver_na2as::init(ast_manager & m, symbol const & logic) {
+    SASSERT(m_assumptions.empty());
+    m_manager = &m;
+    init_core(m, logic);
+}
+
+struct append_assumptions {
+    ptr_vector<expr> & m_assumptions;
+    unsigned           m_old_sz;
+    append_assumptions(ptr_vector<expr> & _m_assumptions, 
+                       unsigned num_assumptions, 
+                       expr * const * assumptions):
+        m_assumptions(_m_assumptions) {
+        m_old_sz = m_assumptions.size();
+        m_assumptions.append(num_assumptions, assumptions);
+    }
+
+    ~append_assumptions() {
+        m_assumptions.shrink(m_old_sz);
+    }
+};
+
+lbool solver_na2as::check_sat(unsigned num_assumptions, expr * const * assumptions) {
+    append_assumptions app(m_assumptions, num_assumptions, assumptions);
+    return check_sat_core(num_assumptions, assumptions);
+}
+
+void solver_na2as::push() {
+    m_scopes.push_back(m_assumptions.size());
+    push_core();
+}
+
+void solver_na2as::pop(unsigned n) {
+    pop_core(n);
+    unsigned lvl = m_scopes.size();
+    SASSERT(n <= lvl);
+    unsigned new_lvl = lvl - n;
+    restore_assumptions(m_scopes[new_lvl]);
+    m_scopes.shrink(new_lvl);
+}
+
+void solver_na2as::restore_assumptions(unsigned old_sz) {
+    SASSERT(m_manager);
+    for (unsigned i = old_sz; i < m_assumptions.size(); i++) {
+        m_manager->dec_ref(m_assumptions[i]);
+    }
+    m_assumptions.shrink(old_sz);
+}
+
+unsigned solver_na2as::get_scope_level() const {
+    return m_scopes.size();
+}
+
+void solver_na2as::reset() {
+    if (m_manager)
+        restore_assumptions(0);
+}