Prefer using empty rather than size comparisons.

src/muz/base/dl_rule_set.h

@@ -230,7 +230,7 @@ namespace datalog {
         bool is_closed() const { return m_stratifier != 0; }
 
         unsigned get_num_rules() const { return m_rules.size(); }
-        bool empty() const { return m_rules.size() == 0; }
+        bool empty() const { return m_rules.empty(); }
 
         rule * get_rule(unsigned i) const { return m_rules[i]; }
         rule * last() const { return m_rules[m_rules.size()-1]; }

src/muz/bmc/dl_bmc_engine.cpp

@@ -986,7 +986,7 @@ namespace datalog {
                 m_sort2pred.insert(new_sorts[i].get(), it->m_key);
                 m_pinned.push_back(new_sorts[i].get());
             }
-            if (new_sorts.size() > 0) {
+            if (!new_sorts.empty()) {
                 TRACE("bmc", dtu.display_datatype(new_sorts[0].get(), tout););
             }
             del_datatype_decls(dts.size(), dts.c_ptr());

src/muz/fp/datalog_parser.cpp

@@ -1057,7 +1057,7 @@ protected:
             line.push_back(ch);
             ch = strm.get();
         }
-        return line.size() > 0;
+        return !line.empty();
     }
 
     void add_rule(app* head, unsigned sz, app* const* body, const bool * is_neg) {

src/muz/rel/dl_finite_product_relation.cpp

@@ -487,7 +487,7 @@ namespace datalog {
 
             res->init(*res_table, joined_orelations, true);
 
-            if(m_tr_table_joined_cols.size()) {
+            if(!m_tr_table_joined_cols.empty()) {
                 //There were some shared variables between the table and the relation part.
                 //We enforce those equalities here.
                 if(!m_filter_tr_identities) {

src/muz/rel/dl_sieve_relation.h

@@ -170,7 +170,7 @@ namespace datalog {
             SASSERT(is_inner_col(idx));
             return m_sig2inner[idx];
         }
-        bool no_sieved_columns() const { return m_ignored_cols.size()==0; }
+        bool no_sieved_columns() const { return m_ignored_cols.empty(); }
         bool no_inner_columns() const { return m_ignored_cols.size()==get_signature().size(); }
 
         relation_base & get_inner() { return *m_inner; }

src/muz/rel/dl_sparse_table.cpp

@@ -1216,7 +1216,7 @@ namespace datalog {
            
             verbose_action  _va("filter_by_negation");
 
-            if (m_cols1.size() == 0) {
+            if (m_cols1.empty()) {
                 if (!neg.empty()) {
                     tgt.reset();
                 }

src/muz/rel/dl_sparse_table.h

@@ -72,7 +72,7 @@ namespace datalog {
         ~sparse_table_plugin() override;
 
         bool can_handle_signature(const table_signature & s) override
-        { return s.size()>0; }
+        { return !s.empty(); }
 
         table_base * mk_empty(const table_signature & s) override;
         sparse_table * mk_clone(const sparse_table & t);

src/muz/spacer/spacer_context.cpp

@@ -3058,7 +3058,7 @@ expr_ref context::get_ground_sat_answer() const {
                 ground_fact_conjs.push_back(m.mk_eq(sig_arg, sig_val));
                 ground_arg_vals.push_back(sig_val);
             }
-            if (ground_fact_conjs.size () > 0) {
+            if (!ground_fact_conjs.empty()) {
                 expr_ref ground_fact(m);
                 ground_fact = mk_and(ground_fact_conjs);
                 m_pm.formula_o2n(ground_fact, ground_fact, i);

src/muz/spacer/spacer_iuc_solver.cpp

@@ -72,7 +72,7 @@ app* iuc_solver::mk_proxy (expr *v)
         if (is_uninterp_const(e)) { return to_app(v); }
     }
 
-    def_manager &def = m_defs.size () > 0 ? m_defs.back () : m_base_defs;
+    def_manager &def = !m_defs.empty() ? m_defs.back () : m_base_defs;
     return def.mk_proxy (v);
 }
 

src/muz/transforms/dl_mk_array_instantiation.cpp

@@ -253,7 +253,7 @@ namespace datalog {
         all_selects.push_back(rewrite_select(array, select_ops[i]));
       }
     }
-    if(all_selects.size()==0)
+    if(all_selects.empty())
     {
       expr_ref_vector dummy_args(m);
       dummy_args.push_back(array);