From 89ffb45c4f94a7d6a857d3c24563727a12f11f0b Mon Sep 17 00:00:00 2001
From: Nikolaj Bjorner <nbjorner@microsoft.com>
Date: Sun, 8 Nov 2020 17:17:43 -0800
Subject: [PATCH] fixes to bv/dual-solver,

---
 src/ast/arith_decl_plugin.h          |  2 +-
 src/ast/euf/euf_egraph.cpp           | 23 ++++++++++++++---
 src/ast/euf/euf_egraph.h             |  1 +
 src/ast/euf/euf_enode.h              |  2 +-
 src/math/lp/lar_solver.cpp           |  9 +++----
 src/math/lp/lar_solver.h             |  2 +-
 src/sat/smt/arith_solver.cpp         |  1 -
 src/sat/smt/arith_solver.h           |  2 +-
 src/sat/smt/array_axioms.cpp         | 13 +++++-----
 src/sat/smt/array_internalize.cpp    |  1 +
 src/sat/smt/array_solver.cpp         |  5 +++-
 src/sat/smt/array_solver.h           |  1 +
 src/sat/smt/bv_delay_internalize.cpp |  4 +--
 src/sat/smt/bv_internalize.cpp       | 37 ++++++----------------------
 src/sat/smt/bv_solver.cpp            | 22 +++++------------
 src/sat/smt/bv_solver.h              |  6 ++---
 src/sat/smt/euf_internalize.cpp      |  4 ++-
 src/sat/smt/sat_dual_solver.cpp      | 31 ++++++++++++++++++++---
 src/sat/smt/sat_dual_solver.h        |  3 +++
 19 files changed, 94 insertions(+), 75 deletions(-)

diff --git a/src/ast/arith_decl_plugin.h b/src/ast/arith_decl_plugin.h
index ff6d21ab1..19f17cada 100644
--- a/src/ast/arith_decl_plugin.h
+++ b/src/ast/arith_decl_plugin.h
@@ -245,7 +245,7 @@ public:
     bool is_unsigned(expr const * n, unsigned& u) const { 
         rational val;
         bool is_int = true;
-        return is_numeral(n, val, is_int) && is_int && val.is_unsigned(), u = val.get_unsigned(), true; 
+        return is_numeral(n, val, is_int) && is_int && val.is_unsigned() && (u = val.get_unsigned(), true); 
     }
     bool is_numeral(expr const * n, rational & val, bool & is_int) const;
     bool is_numeral(expr const * n, rational & val) const { bool is_int; return is_numeral(n, val, is_int); }
diff --git a/src/ast/euf/euf_egraph.cpp b/src/ast/euf/euf_egraph.cpp
index 2fc4629c9..2e55b7865 100644
--- a/src/ast/euf/euf_egraph.cpp
+++ b/src/ast/euf/euf_egraph.cpp
@@ -95,7 +95,7 @@ unmerge(a,a')
 - n1 is reinserted. It used to be a root.
 
 
---*/
+*/
 
 #include "ast/euf/euf_egraph.h"
 #include "ast/ast_pp.h"
@@ -317,11 +317,22 @@ namespace euf {
 
     void egraph::set_merge_enabled(enode* n, bool enable_merge) {
         if (enable_merge != n->merge_enabled()) {
+            toggle_merge_enabled(n);
             m_updates.push_back(update_record(n, update_record::toggle_merge()));
-            n->set_merge_enabled(enable_merge);
         }
     }
 
+    void egraph::toggle_merge_enabled(enode* n) {
+       bool enable_merge = !n->merge_enabled();
+       n->set_merge_enabled(enable_merge);         
+       if (n->num_args() > 0) {
+           if (enable_merge)
+               insert_table(n);
+           else
+               m_table.erase(n);
+       }
+    }
+
     void egraph::set_value(enode* n, lbool value) {        
         force_push();
         TRACE("euf", tout << bpp(n) << "\n";);
@@ -362,7 +373,7 @@ namespace euf {
                 undo_node();
                 break;
             case update_record::tag_t::is_toggle_merge:
-                p.r1->set_merge_enabled(!p.r1->merge_enabled());
+                toggle_merge_enabled(p.r1);
                 break;
             case update_record::tag_t::is_set_parent:
                 undo_eq(p.r1, p.n1, p.r2_num_parents);
@@ -520,6 +531,12 @@ namespace euf {
         for (enode* c : enode_class(r1))
             c->m_root = r1;
 
+        for (enode* p : enode_parents(r1)) 
+            if (p->merge_enabled() && !p->is_cgr() && !p->m_cg) {
+               std::cout << bpp(p) << "\n";
+SASSERT(false);
+        }
+
         for (enode* p : enode_parents(r1)) 
             if (p->merge_enabled() && (p->is_cgr() || !p->congruent(p->m_cg))) 
                 insert_table(p);                    
diff --git a/src/ast/euf/euf_egraph.h b/src/ast/euf/euf_egraph.h
index 48362a672..1c01bd4a2 100644
--- a/src/ast/euf/euf_egraph.h
+++ b/src/ast/euf/euf_egraph.h
@@ -196,6 +196,7 @@ namespace euf {
         void push_to_lca(enode* a, enode* lca);
         void push_congruence(enode* n1, enode* n2, bool commutative);
         void push_todo(enode* n);
+        void toggle_merge_enabled(enode* n);
 
         enode_bool_pair insert_table(enode* p);
 
diff --git a/src/ast/euf/euf_enode.h b/src/ast/euf/euf_enode.h
index 39e56611f..fe7371ab6 100644
--- a/src/ast/euf/euf_enode.h
+++ b/src/ast/euf/euf_enode.h
@@ -138,7 +138,7 @@ namespace euf {
         bool is_cgr() const { return this == m_cg; }
         bool commutative() const { return m_commutative; }
         void mark_interpreted() { SASSERT(num_args() == 0); m_interpreted = true; }
-        bool merge_enabled() { return m_merge_enabled; }
+        bool merge_enabled() const { return m_merge_enabled; }
 
         enode* get_arg(unsigned i) const { SASSERT(i < num_args()); return m_args[i]; }        
         unsigned hash() const { return m_expr->hash(); }
diff --git a/src/math/lp/lar_solver.cpp b/src/math/lp/lar_solver.cpp
index 351d7608e..14368328f 100644
--- a/src/math/lp/lar_solver.cpp
+++ b/src/math/lp/lar_solver.cpp
@@ -1192,10 +1192,10 @@ namespace lp {
 
     impq lar_solver::get_tv_ivalue(tv const& t) const {
         if (t.is_var())
-            return get_ivalue(t.column());
+            return get_column_value(t.column());
         impq r;
         for (const auto& p : get_term(t)) 
-            r += p.coeff() * get_ivalue(p.column());
+            r += p.coeff() * get_column_value(p.column());
         return r;
     }
 
@@ -1317,9 +1317,8 @@ namespace lp {
 
     void lar_solver::mark_rows_for_bound_prop(lpvar j) {
         auto& column = A_r().m_columns[j];
-        for (auto const& r : column) {
-            m_rows_with_changed_bounds.insert(r.var());
-        }
+        for (auto const& r : column) 
+            m_rows_with_changed_bounds.insert(r.var());        
     }
 
 
diff --git a/src/math/lp/lar_solver.h b/src/math/lp/lar_solver.h
index a5df070e1..57c4453a4 100644
--- a/src/math/lp/lar_solver.h
+++ b/src/math/lp/lar_solver.h
@@ -638,7 +638,7 @@ public:
     inline const static_matrix<mpq, impq> & A_r() const { return m_mpq_lar_core_solver.m_r_A; }
     // columns
     bool column_is_int(column_index const& j) const { return column_is_int((unsigned)j); }
-    const impq& get_ivalue(column_index const& j) const { return get_column_value(j); }
+//    const impq& get_ivalue(column_index const& j) const { return get_column_value(j); }
     const impq& get_column_value(column_index const& j) const { return m_mpq_lar_core_solver.m_r_x[j]; }
     inline
     var_index external_to_local(unsigned j) const {
diff --git a/src/sat/smt/arith_solver.cpp b/src/sat/smt/arith_solver.cpp
index 57d929c21..bb3336cd7 100644
--- a/src/sat/smt/arith_solver.cpp
+++ b/src/sat/smt/arith_solver.cpp
@@ -51,7 +51,6 @@ namespace arith {
 
     solver::~solver() {
         del_bounds(0);
-        std::for_each(m_internalize_states.begin(), m_internalize_states.end(), delete_proc<internalize_state>());
     }
 
     void solver::asserted(literal l) {
diff --git a/src/sat/smt/arith_solver.h b/src/sat/smt/arith_solver.h
index 044d76989..cd66c00ad 100644
--- a/src/sat/smt/arith_solver.h
+++ b/src/sat/smt/arith_solver.h
@@ -111,7 +111,7 @@ namespace arith {
                 m_to_ensure_var.reset();
             }
         };
-        ptr_vector<internalize_state> m_internalize_states;
+        scoped_ptr_vector<internalize_state> m_internalize_states;
         unsigned                      m_internalize_head{ 0 };
 
         class scoped_internalize_state {
diff --git a/src/sat/smt/array_axioms.cpp b/src/sat/smt/array_axioms.cpp
index 69b589330..4d7a644c5 100644
--- a/src/sat/smt/array_axioms.cpp
+++ b/src/sat/smt/array_axioms.cpp
@@ -223,6 +223,9 @@ namespace array {
             args1.push_back(k);
             args2.push_back(k);
         }
+        std::cout << "e1: " << mk_pp(e1, m) << "\n";
+        std::cout << "e2: " << mk_pp(e2, m) << "\n";
+        std::cout << "funcs: " << funcs << "\n";
         expr_ref sel1(a.mk_select(args1), m);
         expr_ref sel2(a.mk_select(args2), m);
         literal lit1 = eq_internalize(e1, e2);
@@ -521,13 +524,11 @@ namespace array {
         for (unsigned i = 0; i < num_vars; i++) {
             euf::enode * n = var2enode(i);
             
-            if (!a.is_array(n->get_expr())) {
-                continue;
-            }
+            if (!is_array(n)) 
+                continue;            
             euf::enode * r = n->get_root();
-            if (r->is_marked1()) {
-                continue;
-            }
+            if (r->is_marked1()) 
+                continue;            
             // arrays used as indices in other arrays have to be treated as shared issue #3532, #3529            
             if (ctx.is_shared(r) || is_select_arg(r)) 
                 roots.push_back(r->get_th_var(get_id()));
diff --git a/src/sat/smt/array_internalize.cpp b/src/sat/smt/array_internalize.cpp
index 19caa7222..3e2ca6cd8 100644
--- a/src/sat/smt/array_internalize.cpp
+++ b/src/sat/smt/array_internalize.cpp
@@ -86,6 +86,7 @@ namespace array {
     }
 
     void solver::internalize_ext(euf::enode* n) {
+        SASSERT(is_array(n->get_arg(0)));
         push_axiom(extensionality_axiom(n->get_arg(0), n->get_arg(1)));
     }
 
diff --git a/src/sat/smt/array_solver.cpp b/src/sat/smt/array_solver.cpp
index 3a8913760..02d7ce1dd 100644
--- a/src/sat/smt/array_solver.cpp
+++ b/src/sat/smt/array_solver.cpp
@@ -165,7 +165,10 @@ namespace array {
 
     void solver::new_diseq_eh(euf::th_eq const& eq) {
         force_push();
-        push_axiom(extensionality_axiom(var2enode(eq.v1()), var2enode(eq.v2())));
+        euf::enode* n1 = var2enode(eq.v1());
+        euf::enode* n2 = var2enode(eq.v2());
+        if (is_array(n1))
+            push_axiom(extensionality_axiom(n1, n2));
     }
 
     bool solver::unit_propagate() {
diff --git a/src/sat/smt/array_solver.h b/src/sat/smt/array_solver.h
index 4fbd70e92..6fef43bec 100644
--- a/src/sat/smt/array_solver.h
+++ b/src/sat/smt/array_solver.h
@@ -158,6 +158,7 @@ namespace array {
         void collect_shared_vars(sbuffer<theory_var>& roots);
         bool add_interface_equalities();
         bool is_select_arg(euf::enode* r);
+        bool is_array(euf::enode* n) const { return a.is_array(n->get_expr()); }
 
         // solving          
         void add_parent_select(theory_var v_child, euf::enode* select);
diff --git a/src/sat/smt/bv_delay_internalize.cpp b/src/sat/smt/bv_delay_internalize.cpp
index a10104a80..55d1dd877 100644
--- a/src/sat/smt/bv_delay_internalize.cpp
+++ b/src/sat/smt/bv_delay_internalize.cpp
@@ -176,10 +176,10 @@ namespace bv {
                 args[i] = arg_value;
                 expr_ref r(m.mk_app(n->get_decl(), args), m);
                 set_delay_internalize(r, internalize_mode::init_bits_only_i); // do not bit-blast this multiplier.
-                args[i] = n->get_arg(i);
-                std::cout << "@" << s().scope_lvl() << "\n";
+                args[i] = n->get_arg(i);                
                 add_unit(eq_internalize(r, arg_value));
             }
+            IF_VERBOSE(0, verbose_stream() << "delay internalize @" << s().scope_lvl() << "\n");
             return false;
         }
         if (bv.is_zero(mul_value)) {
diff --git a/src/sat/smt/bv_internalize.cpp b/src/sat/smt/bv_internalize.cpp
index ef64e4f01..cb0fc9e17 100644
--- a/src/sat/smt/bv_internalize.cpp
+++ b/src/sat/smt/bv_internalize.cpp
@@ -133,6 +133,9 @@ namespace bv {
         euf::enode* n = expr2enode(e);
         app* a = to_app(e);
 
+        if (visited(e))
+            return true;
+
         SASSERT(!n || !n->is_attached_to(get_id()));
         bool suppress_args = !get_config().m_bv_reflect && !m.is_considered_uninterpreted(a->get_decl());
         if (!n)
@@ -294,27 +297,12 @@ namespace bv {
         atom* a = get_bv2a(bv);
         if (a)
             return a;
-        a = new (get_region()) atom();
+        a = new (get_region()) atom(bv);
         insert_bv2a(bv, a);
         ctx.push(mk_atom_trail(bv, *this));
         return a;        
     }
 
-#if 0
-    solver::eq_atom* solver::mk_eq_atom(sat::bool_var bv) {
-        atom* a = get_bv2a(bv);
-        if (a)
-            return a->is_eq() ? &a->to_eq() : nullptr;
-        else {
-            eq_atom* b = new (get_region()) eq_atom();
-            insert_bv2a(bv, b);
-            ctx.push(mk_atom_trail(bv, *this));
-            return b;
-        }
-    }
-#endif
-
-
     void solver::set_bit_eh(theory_var v, literal l, unsigned idx) {
         SASSERT(m_bits[v][idx] == l);
         if (s().value(l) != l_undef && s().lvl(l) == 0) 
@@ -323,8 +311,7 @@ namespace bv {
             atom* b = mk_atom(l.var());
             if (b->m_occs)
                 find_new_diseq_axioms(*b, v, idx);
-            if (!b->is_fresh())
-                ctx.push(add_var_pos_trail(b));
+            ctx.push(add_var_pos_trail(b));
             b->m_occs = new (get_region()) var_pos_occ(v, idx, b->m_occs);
         }
     }
@@ -586,7 +573,7 @@ namespace bv {
     }
 
     void solver::add_def(sat::literal def, sat::literal l) {        
-        atom* a = new (get_region()) atom();
+        atom* a = new (get_region()) atom(l.var());
         a->m_var = l;
         a->m_def = def;
         insert_bv2a(l.var(), a);
@@ -648,7 +635,7 @@ namespace bv {
             m_bits[v_arg][idx] = lit;
             TRACE("bv", tout << "add-bit: " << lit << " " << literal2expr(lit) << "\n";);
             if (arg_sz > 1) {
-                atom* a = new (get_region()) atom();
+                atom* a = new (get_region()) atom(lit.var());
                 a->m_occs = new (get_region()) var_pos_occ(v_arg, idx);
                 insert_bv2a(lit.var(), a);
                 ctx.push(mk_atom_trail(lit.var(), *this));
@@ -713,20 +700,12 @@ namespace bv {
 
     void solver::eq_internalized(sat::bool_var b1, sat::bool_var b2, unsigned idx, theory_var v1, theory_var v2, literal lit, euf::enode* n) {
         atom* a = mk_atom(b1);
-//        eq_atom* b = mk_eq_atom(lit.var());
         if (a) {
-            if (!a->is_fresh()) 
-                ctx.push(add_eq_occurs_trail(a));            
+            ctx.push(add_eq_occurs_trail(a));            
             auto* next = a->m_eqs;
             a->m_eqs = new (get_region()) eq_occurs(b1, b2, idx, v1, v2, lit, n, next);
             if (next)
                 next->m_prev = a->m_eqs;
-#if 0
-            if (b) {
-                b->m_eqs.push_back(std::make_pair(a, a->m_eqs));
-                ctx.push(push_back_vector<euf::solver, svector<std::pair<bit_atom*,eq_occurs*>>>(b->m_eqs));
-            }
-#endif
         }        
     }
 
diff --git a/src/sat/smt/bv_solver.cpp b/src/sat/smt/bv_solver.cpp
index 8e82cad8e..e1cdfa312 100644
--- a/src/sat/smt/bv_solver.cpp
+++ b/src/sat/smt/bv_solver.cpp
@@ -44,7 +44,6 @@ namespace bv {
         bit_occs_trail(solver& s, atom& a): a(a), m_occs(a.m_occs) {}
         
         virtual void undo(euf::solver& euf) {
-            IF_VERBOSE(1, verbose_stream() << "add back occurrences " << & a << "\n");
             a.m_occs = m_occs;
         }
     };
@@ -400,20 +399,10 @@ namespace bv {
         for (; m_prop_queue_head < m_prop_queue.size() && !s().inconsistent(); ++m_prop_queue_head) {
             auto const p = m_prop_queue[m_prop_queue_head];
             if (p.m_atom) {
-                unsigned num_atoms = 0, num_eqs = 0, num_assigned = 0, num_eq_assigned = 0, num_lit_assigned = 0;
-                for (auto vp : *p.m_atom) {
-                    if (propagate_bits(vp))
-                        ++num_assigned;
-                    ++num_atoms;
-                }
-                for (auto const& eq : p.m_atom->eqs()) {
-                    ++num_eqs;
-                    if (s().value(eq.m_literal) != l_undef)
-                        ++num_lit_assigned;
-                    if (propagate_eq_occurs(eq)) {
-                        ++num_eq_assigned;
-                    }
-                }
+                for (auto vp : *p.m_atom)
+                    propagate_bits(vp);
+                for (auto const& eq : p.m_atom->eqs()) 
+                    propagate_eq_occurs(eq);                
             }
             else 
                 propagate_bits(p.m_vp);            
@@ -669,7 +658,7 @@ namespace bv {
             if (!a)
                 continue;
 
-            atom* new_a = new (result->get_region()) atom();
+            atom* new_a = new (result->get_region()) atom(i);
             m_bool_var2atom.setx(i, new_a, nullptr);
             for (auto vp : *a)
                 new_a->m_occs = new (result->get_region()) var_pos_occ(vp.first, vp.second, new_a->m_occs);
@@ -800,6 +789,7 @@ namespace bv {
                 find_wpos(v2);
             bool_var cv = consequent.var();
             atom* a = get_bv2a(cv);
+            force_push();
             if (a)
                 for (auto curr : *a)
                     if (propagate_eqc || find(curr.first) != find(v2) || curr.second != idx) 
diff --git a/src/sat/smt/bv_solver.h b/src/sat/smt/bv_solver.h
index 87dede42b..67f5d56cb 100644
--- a/src/sat/smt/bv_solver.h
+++ b/src/sat/smt/bv_solver.h
@@ -126,7 +126,7 @@ namespace bv {
             eq_occurs_it(eq_occurs* c) : m_first(c) {}
             eq_occurs operator*() { return *m_first; }
             eq_occurs_it& operator++() { m_first = m_first->m_next; return *this; }
-            eq_occurs_it operator++(int) { eq_occurs_it tmp = *this; ++* this; return tmp; }
+            eq_occurs_it operator++(int) { eq_occurs_it tmp = *this; ++*this; return tmp; }
             bool operator==(eq_occurs_it const& other) const { return m_first == other.m_first; }
             bool operator!=(eq_occurs_it const& other) const { return !(*this == other); }
         };
@@ -157,16 +157,16 @@ namespace bv {
         };
 
         struct atom {
+            bool_var      m_bv;
             eq_occurs*    m_eqs;
             var_pos_occ * m_occs;
             svector<std::pair<atom*, eq_occurs*>> m_bit2occ;
             literal    m_var { sat::null_literal };
             literal    m_def { sat::null_literal };
-            atom() :m_eqs(nullptr), m_occs(nullptr) {}
+            atom(bool_var b) :m_bv(b), m_eqs(nullptr), m_occs(nullptr) {}
             ~atom() { m_bit2occ.clear(); }
             var_pos_it begin() const { return var_pos_it(m_occs); }
             var_pos_it end() const { return var_pos_it(nullptr); }
-            bool is_fresh() const { return !m_occs && !m_eqs; }
             eqs_iterator eqs() const { return eqs_iterator(m_eqs); }  
         };
 
diff --git a/src/sat/smt/euf_internalize.cpp b/src/sat/smt/euf_internalize.cpp
index b31a7090e..0dff8380a 100644
--- a/src/sat/smt/euf_internalize.cpp
+++ b/src/sat/smt/euf_internalize.cpp
@@ -104,7 +104,7 @@ namespace euf {
         sat::literal lit;
         if (!m.is_bool(e))
             drat_log_node(e);
-        else
+        else 
             lit = attach_lit(literal(si.add_bool_var(e), false), e);
 
         if (!m.is_bool(e) && m.get_sort(e)->get_family_id() != null_family_id) {
@@ -153,6 +153,8 @@ namespace euf {
         m_egraph.set_bool_var(n, v);
         if (m.is_eq(e) || m.is_or(e) || m.is_and(e) || m.is_not(e))
             m_egraph.set_merge_enabled(n, false);
+        if (!si.is_bool_op(e))
+            track_relevancy(lit.var());
         return lit;
     }
 
diff --git a/src/sat/smt/sat_dual_solver.cpp b/src/sat/smt/sat_dual_solver.cpp
index 3d0411570..96881bc5c 100644
--- a/src/sat/smt/sat_dual_solver.cpp
+++ b/src/sat/smt/sat_dual_solver.cpp
@@ -90,19 +90,42 @@ namespace sat {
     }
 
     bool dual_solver::operator()(solver const& s) {
+        m_core.reset();
+        m_core.append(m_units);
+        if (m_roots.empty())
+            return true;
         m_solver.user_push();
         m_solver.add_clause(m_roots.size(), m_roots.c_ptr(), status::input());
         m_lits.reset();
         for (bool_var v : m_tracked_vars)
             m_lits.push_back(literal(v, l_false == s.value(m_var2ext[v])));
         lbool is_sat = m_solver.check(m_lits.size(), m_lits.c_ptr());
-        m_core.reset();
-        m_core.append(m_units);
         if (is_sat == l_false) 
             for (literal lit : m_solver.get_core())
-                m_core.push_back(lit2ext(lit));
-        TRACE("euf", m_solver.display(tout << "is-sat: " << is_sat << " core: " << m_core << "\n"););
+                m_core.push_back(lit2ext(lit));        
+        if (is_sat == l_true) {
+            IF_VERBOSE(0, display(s, verbose_stream()));
+            UNREACHABLE();
+        }
+        TRACE("dual", m_solver.display(tout << "is-sat: " << is_sat << " core: " << m_core << "\n"););
         m_solver.user_pop(1);
         return is_sat == l_false;
     }
+
+
+    std::ostream& dual_solver::display(solver const& s, std::ostream& out) const {
+        for (auto r : m_roots)
+            out << r << " " << m_solver.value(r) << "\n";
+        for (unsigned v = 0; v < m_solver.num_vars(); ++v) {
+            bool_var w = m_var2ext.get(v, null_bool_var);
+            if (w == null_bool_var)
+                continue;
+            lbool v1 = m_solver.value(v);
+            lbool v2 = s.value(w);
+            if (v1 == v2)
+                continue;
+            out << w << " " << v1 << " " << v2 << "\n";
+        }
+        return out;
+    }
 }
diff --git a/src/sat/smt/sat_dual_solver.h b/src/sat/smt/sat_dual_solver.h
index 9f27a8306..e31922b41 100644
--- a/src/sat/smt/sat_dual_solver.h
+++ b/src/sat/smt/sat_dual_solver.h
@@ -40,6 +40,9 @@ namespace sat {
         bool_var var2ext(bool_var v);
         literal  ext2lit(literal lit);
         literal  lit2ext(literal lit);
+
+        std::ostream& display(solver const& s, std::ostream& out) const;
+
     public:
         dual_solver(reslimit& l);
         void push();