diff --git a/.clang-tidy b/.clang-tidy
index 583e5c654c..92a9493030 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -3,6 +3,7 @@ Checks: [-*,
          performance-*,
          modernize-*,
          readability-isolate-declaration,
+         readability-container-contains,
 
          # Enable a very limited number of the cppcoreguidelines checkers.
          # See the notes for some of the rest of them below.
diff --git a/CHANGES b/CHANGES
index 7b399295f5..d5fa900ce3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,13 @@
+8.1.0-dev.490 | 2025-09-02 11:47:44 -0700
+
+  * Fix a few more random clang-tidy findings (Tim Wojtulewicz, Corelight)
+
+  * Use std::numbers::pi instead of hard-coded value (Tim Wojtulewicz, Corelight)
+  
+  * Use std::scoped_lock instead of std::lock_guard (Tim Wojtulewicz, Corelight)
+
+  * Use .contains() instead of .find() or .count() (Tim Wojtulewicz, Corelight)
+
 8.1.0-dev.484 | 2025-08-29 21:53:19 -0700
 
   * Bump zeek-testing-cluster to pull in WebSocket TLS updates (Christian Kreibich, Corelight)
diff --git a/VERSION b/VERSION
index 5d67fa6322..db10e881ec 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-8.1.0-dev.484
+8.1.0-dev.490
diff --git a/src/DNS_Mgr.cc b/src/DNS_Mgr.cc
index 2272163ba6..190c085a36 100644
--- a/src/DNS_Mgr.cc
+++ b/src/DNS_Mgr.cc
@@ -473,20 +473,20 @@ void DNS_Mgr::Done() {
 }
 
 void DNS_Mgr::RegisterSocket(int fd, bool read, bool write) {
-    if ( read && socket_fds.count(fd) == 0 ) {
+    if ( read && ! socket_fds.contains(fd) ) {
         socket_fds.insert(fd);
         iosource_mgr->RegisterFd(fd, this, IOSource::READ);
     }
-    else if ( ! read && socket_fds.count(fd) != 0 ) {
+    else if ( ! read && socket_fds.contains(fd) ) {
         socket_fds.erase(fd);
         iosource_mgr->UnregisterFd(fd, this, IOSource::READ);
     }
 
-    if ( write && write_socket_fds.count(fd) == 0 ) {
+    if ( write && ! write_socket_fds.contains(fd) ) {
         write_socket_fds.insert(fd);
         iosource_mgr->RegisterFd(fd, this, IOSource::WRITE);
     }
-    else if ( ! write && write_socket_fds.count(fd) != 0 ) {
+    else if ( ! write && write_socket_fds.contains(fd) ) {
         write_socket_fds.erase(fd);
         iosource_mgr->UnregisterFd(fd, this, IOSource::WRITE);
     }
@@ -1323,7 +1323,7 @@ double DNS_Mgr::GetNextTimeout() {
 }
 
 void DNS_Mgr::ProcessFd(int fd, int flags) {
-    if ( socket_fds.count(fd) != 0 ) {
+    if ( socket_fds.contains(fd) ) {
         int read_fd = (flags & IOSource::ProcessFlags::READ) != 0 ? fd : ARES_SOCKET_BAD;
         int write_fd = (flags & IOSource::ProcessFlags::WRITE) != 0 ? fd : ARES_SOCKET_BAD;
         ares_process_fd(channel, read_fd, write_fd);
diff --git a/src/DebugLogger.cc b/src/DebugLogger.cc
index 7e6a9e87e1..bde819fbf8 100644
--- a/src/DebugLogger.cc
+++ b/src/DebugLogger.cc
@@ -148,7 +148,7 @@ bool DebugLogger::CheckStreams(const std::set<std::string>& plugin_names) {
         if ( ! stream.starts_with("plugin-") )
             continue;
 
-        if ( available_plugin_streams.count(stream) == 0 ) {
+        if ( ! available_plugin_streams.contains(stream) ) {
             reporter->Error("No plugin debug stream '%s' found", stream.c_str());
             ok = false;
         }
@@ -180,7 +180,7 @@ void DebugLogger::Log(DebugStream stream, const char* fmt, ...) {
 void DebugLogger::Log(const plugin::Plugin& plugin, const char* fmt, ...) {
     if ( ! all ) {
         std::string tok = PluginStreamName(plugin.Name());
-        if ( enabled_streams.find(tok) == enabled_streams.end() )
+        if ( ! enabled_streams.contains(tok) )
             return;
     }
 
diff --git a/src/EventRegistry.cc b/src/EventRegistry.cc
index 48fea80a09..8793a951cc 100644
--- a/src/EventRegistry.cc
+++ b/src/EventRegistry.cc
@@ -55,7 +55,7 @@ EventHandler* EventRegistry::Lookup(std::string_view name) {
 }
 
 bool EventRegistry::NotOnlyRegisteredFromScript(std::string_view name) {
-    return not_only_from_script.count(std::string(name)) > 0;
+    return not_only_from_script.contains(std::string(name));
 }
 
 EventRegistry::string_list EventRegistry::Match(RE_Matcher* pattern) {
@@ -174,12 +174,12 @@ namespace {
 class EventMetadataTypeRejector : public detail::TraversalCallback {
 public:
     detail::TraversalCode PreType(const Type* t) override {
-        if ( visited.count(t) > 0 )
+        if ( visited.contains(t) )
             return detail::TC_ABORTSTMT;
 
         visited.insert(t);
 
-        if ( reject.count(t->Tag()) )
+        if ( reject.contains(t->Tag()) )
             rejected.push_back(t);
 
         return detail::TC_CONTINUE;
diff --git a/src/EventTrace.cc b/src/EventTrace.cc
index 3298447e89..a761bf65e3 100644
--- a/src/EventTrace.cc
+++ b/src/EventTrace.cc
@@ -732,7 +732,7 @@ void ValTraceMgr::TraceEventValues(std::shared_ptr<EventTrace> et, const zeek::A
     // remember them so we can catch uses of them in future events.
     for ( auto i = num_vals; i < vals.size(); ++i ) {
         processed_vals.insert(vals[i].get());
-        ASSERT(val_names.count(vals[i].get()) > 0);
+        ASSERT(val_names.contains(vals[i].get()));
     }
 }
 
@@ -794,8 +794,8 @@ void ValTraceMgr::NewVal(ValPtr v) {
 }
 
 void ValTraceMgr::ValUsed(const ValPtr& v) {
-    ASSERT(val_names.count(v.get()) > 0);
-    if ( processed_vals.count(v.get()) > 0 )
+    ASSERT(val_names.contains(v.get()));
+    if ( processed_vals.contains(v.get()) )
         // We saw this value when processing a previous event.
         globals.insert(v.get());
 }
@@ -818,17 +818,17 @@ void ValTraceMgr::AssessChange(const ValTrace* vt, const ValTrace* prev_vt) {
         bool needs_lhs = d->NeedsLHS();
         bool is_first_def = false;
 
-        if ( needs_lhs && val_names.count(v) == 0 ) {
+        if ( needs_lhs && ! val_names.contains(v) ) {
             TrackVar(v);
             is_first_def = true;
         }
 
-        ASSERT(val_names.count(v) > 0);
+        ASSERT(val_names.contains(v));
 
         // The "/" in the following is just to have a delimiter
         // to make sure the string is unambiguous.
         auto full_delta = val_names[v] + "/" + rhs;
-        if ( previous_deltas.count(full_delta) > 0 )
+        if ( previous_deltas.contains(full_delta) )
             continue;
 
         previous_deltas.insert(std::move(full_delta));
@@ -849,7 +849,7 @@ void ValTraceMgr::TrackVar(const Val* v) {
 
 std::string ValTraceMgr::GenValName(const ValPtr& v) {
     if ( IsAggr(v->GetType()) && ! IsUnspecifiedAggregate(v) ) { // Aggregate shouldn't exist; create it
-        ASSERT(val_map.count(v.get()) == 0);
+        ASSERT(! val_map.contains(v.get()));
         NewVal(v);
         return val_names[v.get()];
     }
@@ -1012,7 +1012,7 @@ void EventTraceMgr::Generate() {
 }
 
 void EventTraceMgr::StartEvent(const ScriptFunc* ev, const zeek::Args* args) {
-    if ( script_events.count(ev->GetName()) > 0 )
+    if ( script_events.contains(ev->GetName()) )
         return;
 
     auto nt = run_state::network_time;
@@ -1029,7 +1029,7 @@ void EventTraceMgr::StartEvent(const ScriptFunc* ev, const zeek::Args* args) {
 }
 
 void EventTraceMgr::EndEvent(const ScriptFunc* ev, const zeek::Args* args) {
-    if ( script_events.count(ev->GetName()) > 0 )
+    if ( script_events.contains(ev->GetName()) )
         return;
 
     if ( run_state::network_time > 0.0 && ev->GetName() != "zeek_init" )
diff --git a/src/EventTrace.h b/src/EventTrace.h
index 2e70c6d244..3c5589055f 100644
--- a/src/EventTrace.h
+++ b/src/EventTrace.h
@@ -354,7 +354,7 @@ public:
 
     // Returns true if the script variable associated with the given value
     // needs to be global (because it's used across multiple events).
-    bool IsGlobal(const ValPtr& v) const { return globals.count(v.get()) > 0; }
+    bool IsGlobal(const ValPtr& v) const { return globals.contains(v.get()); }
 
     // Returns or sets the "base time" from which eligible times are
     // transformed into offsets rather than maintained as absolute
diff --git a/src/Expr.cc b/src/Expr.cc
index a0e076443a..d9f456af58 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -2999,7 +2999,7 @@ RecordConstructorExpr::RecordConstructorExpr(RecordTypePtr known_rt, ListExprPtr
 
     auto n = known_rt->NumFields();
     for ( i = 0; i < n; ++i )
-        if ( fields_seen.count(i) == 0 ) {
+        if ( ! fields_seen.contains(i) ) {
             const auto td_i = known_rt->FieldDecl(i);
             if ( IsAggr(td_i->type) )
                 // These are always initialized.
@@ -4307,7 +4307,7 @@ bool LambdaExpr::CheckCaptures(StmtPtr when_parent) {
             // already been an error message.
             continue;
 
-        if ( capture_is_matched.count(cid) > 0 ) {
+        if ( capture_is_matched.contains(cid) ) {
             auto msg = util::fmt("%s listed multiple times in capture", cid->Name());
             if ( when_parent )
                 when_parent->Error(msg);
@@ -4326,7 +4326,7 @@ bool LambdaExpr::CheckCaptures(StmtPtr when_parent) {
     }
 
     for ( auto id : outer_ids )
-        if ( outer_is_matched.count(id) == 0 ) {
+        if ( ! outer_is_matched.contains(id) ) {
             auto msg = util::fmt("%s is used inside %s but not captured", id->Name(), desc);
             if ( when_parent )
                 when_parent->Error(msg);
@@ -4338,7 +4338,7 @@ bool LambdaExpr::CheckCaptures(StmtPtr when_parent) {
 
     for ( const auto& c : *captures ) {
         auto cid = c.Id().get();
-        if ( cid && capture_is_matched.count(cid) == 0 ) {
+        if ( cid && ! capture_is_matched.contains(cid) ) {
             auto msg = util::fmt("%s is captured but not used inside %s", cid->Name(), desc);
             if ( when_parent )
                 when_parent->Error(msg);
diff --git a/src/PolicyFile.cc b/src/PolicyFile.cc
index fb75d8afa3..48e0b1fa0b 100644
--- a/src/PolicyFile.cc
+++ b/src/PolicyFile.cc
@@ -68,7 +68,7 @@ bool LoadPolicyFileText(const char* policy_filename, const std::optional<std::st
     if ( ! policy_filename )
         return true;
 
-    if ( policy_files.find(policy_filename) != policy_files.end() )
+    if ( policy_files.contains(policy_filename) )
         debug_msg("Policy file %s already loaded\n", policy_filename);
 
     PolicyFile* pf = new PolicyFile;
diff --git a/src/Reporter.h b/src/Reporter.h
index ce4fcae7d3..6fc5a68377 100644
--- a/src/Reporter.h
+++ b/src/Reporter.h
@@ -292,12 +292,8 @@ private:
         __attribute__((format(printf, 4, 5)));
     ;
     void UpdateWeirdStats(const char* name);
-    inline bool WeirdOnSamplingWhiteList(const char* name) {
-        return weird_sampling_whitelist.find(name) != weird_sampling_whitelist.end();
-    }
-    inline bool WeirdOnGlobalList(const char* name) {
-        return weird_sampling_global_list.find(name) != weird_sampling_global_list.end();
-    }
+    inline bool WeirdOnSamplingWhiteList(const char* name) { return weird_sampling_whitelist.contains(name); }
+    inline bool WeirdOnGlobalList(const char* name) { return weird_sampling_global_list.contains(name); }
     bool PermitNetWeird(const char* name);
     bool PermitFlowWeird(const char* name, const IPAddr& o, const IPAddr& r);
     bool PermitExpiredConnWeird(const char* name, const RecordVal& conn_id);
diff --git a/src/RuleMatcher.cc b/src/RuleMatcher.cc
index 76c7deefba..08217dc704 100644
--- a/src/RuleMatcher.cc
+++ b/src/RuleMatcher.cc
@@ -334,7 +334,7 @@ bool RuleMatcher::ReadFiles(const std::vector<SignatureFile>& files) {
 }
 
 void RuleMatcher::AddRule(Rule* rule) {
-    if ( rules_by_id.find(rule->ID()) != rules_by_id.end() ) {
+    if ( rules_by_id.contains(rule->ID()) ) {
         rules_error("rule defined twice");
         return;
     }
@@ -602,7 +602,7 @@ bool RuleMatcher::AllRulePatternsMatched(const Rule* r, MatchPos matchpos, const
 
     // Check whether all patterns of the rule have matched.
     for ( const auto& pattern : r->patterns ) {
-        if ( ams.find(pattern->id) == ams.end() )
+        if ( ! ams.contains(pattern->id) )
             return false;
 
         // See if depth is satisfied.
diff --git a/src/ScriptCoverageManager.cc b/src/ScriptCoverageManager.cc
index 5d13cd63a0..e091759e2b 100644
--- a/src/ScriptCoverageManager.cc
+++ b/src/ScriptCoverageManager.cc
@@ -158,7 +158,7 @@ void ScriptCoverageManager::TrackUsage(const Location* loc, std::string desc, ui
 
     pair<string, string> location_desc(location_info.Description(), desc);
 
-    if ( usage_map.find(location_desc) != usage_map.end() )
+    if ( usage_map.contains(location_desc) )
         usage_map[location_desc] += cnt;
     else
         usage_map[location_desc] = cnt;
diff --git a/src/ScriptProfile.cc b/src/ScriptProfile.cc
index a5e6c62619..1e4a47a253 100644
--- a/src/ScriptProfile.cc
+++ b/src/ScriptProfile.cc
@@ -122,10 +122,10 @@ ScriptProfileMgr::~ScriptProfileMgr() {
             BiF_stats.AddIn(p);
         }
         else {
-            ASSERT(body_to_func.count(o) > 0);
+            ASSERT(body_to_func.contains(o));
             auto func = body_to_func[o];
 
-            if ( func_stats.count(func) == 0 )
+            if ( ! func_stats.contains(func) )
                 func_stats[func] = ScriptProfileStats(func->GetName());
 
             func_stats[func].AddIn(p);
diff --git a/src/ScriptValidation.cc b/src/ScriptValidation.cc
index 6660d50377..e38aa2a8a9 100644
--- a/src/ScriptValidation.cc
+++ b/src/ScriptValidation.cc
@@ -59,7 +59,7 @@ public:
     }
 
     TraversalCode PreType(const Type* t) override {
-        if ( types_seen.count(t) > 0 )
+        if ( types_seen.contains(t) )
             return TC_ABORTSTMT;
 
         types_seen.insert(t);
diff --git a/src/Type.cc b/src/Type.cc
index 2d96f636e7..419af89caa 100644
--- a/src/Type.cc
+++ b/src/Type.cc
@@ -415,7 +415,7 @@ static bool is_supported_index_type(const TypePtr& t, const char** tname, std::u
 
     // Handle recursive calls as good: If they turn out not
     // to be, that should've been discovered further down.
-    if ( seen.count(t) > 0 )
+    if ( seen.contains(t) )
         return true;
 
     seen.insert(t);
@@ -1006,7 +1006,7 @@ class RecordType::CreationInitsOptimizer : public detail::TraversalCallback {
 public:
     detail::TraversalCode PreTypedef(const detail::ID* id) override {
         const auto& t = id->GetType();
-        if ( analyzed_types.count(t) > 0 )
+        if ( analyzed_types.contains(t) )
             return detail::TC_ABORTSTMT;
 
         analyzed_types.emplace(t);
@@ -1102,7 +1102,7 @@ void RecordType::AddField(unsigned int field, const TypeDecl* td) {
     // We defer error-checking until here so that we can keep deferred_inits
     // and managed_fields correctly tracking the associated fields.
 
-    if ( field_ids.count(td->id) != 0 ) {
+    if ( field_ids.contains(td->id) ) {
         reporter->Error("duplicate field '%s' found in record definition", td->id);
         deferred_inits.push_back(nullptr);
         return;
@@ -1168,7 +1168,7 @@ void RecordType::AddField(unsigned int field, const TypeDecl* td) {
     deferred_inits.push_back(std::move(init));
 }
 
-bool RecordType::HasField(const char* field) const { return field_ids.count(field) != 0; }
+bool RecordType::HasField(const char* field) const { return field_ids.contains(field); }
 
 ValPtr RecordType::FieldDefault(int field) const {
     const TypeDecl* td = FieldDecl(field);
@@ -1654,8 +1654,7 @@ void EnumType::CheckAndAddName(const string& module_name, const char* name, zeek
         // we can define an enum both in a *.bif and *.zeek for avoiding
         // cyclic dependencies.
         if ( ! id->IsEnumConst() || (id->HasVal() && val != id->GetVal()->AsEnum()) ||
-             GetName() != id->GetType()->GetName() ||
-             (names.find(fullname) != names.end() && names[fullname] != val) ) {
+             GetName() != id->GetType()->GetName() || (names.contains(fullname) && names[fullname] != val) ) {
             auto cl = detail::GetCurrentLocation();
             reporter->PushLocation(&cl, id->GetLocationInfo());
             reporter->Error("conflicting definition of enum value '%s' in type '%s'", fullname.data(),
@@ -1668,7 +1667,7 @@ void EnumType::CheckAndAddName(const string& module_name, const char* name, zeek
 
     AddNameInternal(module_name, name, val, is_export);
 
-    if ( vals.find(val) == vals.end() )
+    if ( ! vals.contains(val) )
         vals[val] = make_intrusive<EnumVal>(IntrusivePtr{NewRef{}, this}, val);
 
     if ( ! id->HasVal() )
@@ -1694,7 +1693,7 @@ void EnumType::AddNameInternal(const string& full_name, zeek_int_t val) {
     names[full_name] = val;
     rev_names[val] = full_name;
 
-    if ( vals.find(val) == vals.end() )
+    if ( ! vals.contains(val) )
         vals[val] = make_intrusive<EnumVal>(IntrusivePtr{NewRef{}, this}, val);
 }
 
@@ -2031,11 +2030,11 @@ bool same_type(const Type& arg_t1, const Type& arg_t2, bool is_init, bool match_
     // If we get to here, then we're dealing with a type with
     // subtypes, and thus potentially recursive.
 
-    if ( analyzed_types.count(t1) > 0 || analyzed_types.count(t2) > 0 ) {
+    if ( analyzed_types.contains(t1) || analyzed_types.contains(t2) ) {
         // We've analyzed at least one of the types previously.
         // Avoid infinite recursion.
 
-        if ( analyzed_types.count(t1) > 0 && analyzed_types.count(t2) > 0 )
+        if ( analyzed_types.contains(t1) && analyzed_types.contains(t2) )
             // We've analyzed them both.  In theory, this
             // could happen while the types are still different.
             // Checking for that is a pain - we could do so
diff --git a/src/Val.cc b/src/Val.cc
index 9214866c56..292a07e791 100644
--- a/src/Val.cc
+++ b/src/Val.cc
@@ -1532,7 +1532,7 @@ static void find_nested_record_types(const TypePtr& t, std::set<RecordType*>* fo
         case TYPE_RECORD: {
             auto rt = t->AsRecordType();
 
-            if ( analyzed_records->count(rt) > 0 )
+            if ( analyzed_records->contains(rt) )
                 return;
 
             analyzed_records->insert(rt);
@@ -2882,7 +2882,7 @@ void TableVal::RebuildParseTimeTables() {
 
     for ( auto& [tv, ptts] : parse_time_table_states ) {
         auto* tt = tv->table_type.get();
-        if ( table_types.count(tt) == 0 ) {
+        if ( ! table_types.contains(tt) ) {
             tt->RegenerateHash();
             table_types.insert(tt);
         }
@@ -4041,7 +4041,7 @@ unsigned int Val::Footprint(std::unordered_set<const Val*>* analyzed_vals) const
     // We only need to check containers for possible recursion, as there's
     // no way to construct a cycle using only non-aggregates.
     if ( is_aggr ) {
-        if ( analyzed_vals->count(this) > 0 )
+        if ( analyzed_vals->contains(this) )
             // Footprint is 1 for generating a cycle.
             return 1;
 
diff --git a/src/analyzer/protocol/irc/IRC.cc b/src/analyzer/protocol/irc/IRC.cc
index aa7b3bc5b1..3fb82db456 100644
--- a/src/analyzer/protocol/irc/IRC.cc
+++ b/src/analyzer/protocol/irc/IRC.cc
@@ -49,7 +49,7 @@ bool IRC_Analyzer::IsValidClientCommand(const std::string& command) {
          "SETNAME", "SILENCE",  "SQUERY",  "SQUIT",    "STATS",   "SUMMON", "TIME",    "TOPIC",    "TRACE",
          "USER",    "USERHOST", "USERS",   "VERSION",  "WALLOPS", "WHO",    "WHOIS",   "WHOWAS",   "STARTTLS"};
 
-    return validCommands.find(command) != validCommands.end();
+    return validCommands.contains(command);
 }
 
 void IRC_Analyzer::DeliverStream(int length, const u_char* line, bool orig) {
diff --git a/src/analyzer/protocol/smb/smb1-com-transaction.pac b/src/analyzer/protocol/smb/smb1-com-transaction.pac
index a2daba3fb1..afa9a93877 100644
--- a/src/analyzer/protocol/smb/smb1-com-transaction.pac
+++ b/src/analyzer/protocol/smb/smb1-com-transaction.pac
@@ -31,7 +31,7 @@ refine connection SMB_Conn += {
 
 	function get_is_file_a_pipe(id: uint16): bool
 		%{
-		if ( is_file_a_pipe.count(id) > 0 )
+		if ( is_file_a_pipe.contains(id) )
 			{
 			bool is_pipe = is_file_a_pipe.at(id);
 			is_file_a_pipe.erase(id);
diff --git a/src/broker/Data.cc b/src/broker/Data.cc
index 466c4f8d7b..6d99f014a6 100644
--- a/src/broker/Data.cc
+++ b/src/broker/Data.cc
@@ -1072,7 +1072,7 @@ bool SetIterator::DoUnserializeData(BrokerDataView data) {
     // This is not perfect, as there's no guarantee that the restored
     // container will list the elements in the same order. But it's as
     // good as we can do, and it should generally work out.
-    if ( x->find((*v)[1]) == x->end() )
+    if ( ! x->contains((*v)[1]) )
         return false;
 
     dat = *x;
@@ -1097,7 +1097,7 @@ bool TableIterator::DoUnserializeData(BrokerDataView data) {
     // This is not perfect, as there's no guarantee that the restored
     // container will list the elements in the same order. But it's as
     // good as we can do, and it should generally work out.
-    if ( x->find((*v)[1]) == x->end() )
+    if ( ! x->contains((*v)[1]) )
         return false;
 
     dat = *x;
diff --git a/src/broker/Manager.cc b/src/broker/Manager.cc
index bd7fd90e1d..cd4d0c8788 100644
--- a/src/broker/Manager.cc
+++ b/src/broker/Manager.cc
@@ -149,7 +149,7 @@ public:
     // arrivals (a push, is_push == true) and departures (a pull, is_push ==
     // false) as they happen. Note that this must not touch Zeek-side Vals.
     void Observe(const broker::endpoint_id& peer, bool is_push) {
-        std::lock_guard<std::mutex> lock(mutex);
+        std::scoped_lock<std::mutex> lock(mutex);
         auto it = stats_map.find(peer);
 
         if ( it == stats_map.end() ) {
@@ -186,7 +186,7 @@ public:
 
     // Updates the internal table[string] of BrokerPeeringStats and returns it.
     const zeek::TableValPtr& GetPeeringStatsTable() {
-        std::lock_guard<std::mutex> lock(mutex);
+        std::scoped_lock<std::mutex> lock(mutex);
 
         for ( auto it = stats_map.begin(); it != stats_map.end(); ) {
             auto& peer = it->first;
@@ -236,7 +236,7 @@ public:
     }
 
     void RemovePeer(const broker::endpoint_id& peer) {
-        std::lock_guard<std::mutex> lock(mutex);
+        std::scoped_lock<std::mutex> lock(mutex);
         if ( auto it = stats_map.find(peer); it != stats_map.end() )
             it->second.is_zombie = true;
     }
@@ -271,7 +271,7 @@ public:
         std::list<broker::event_ptr> tmp;
         tmp.emplace_back(std::move(event));
         {
-            std::lock_guard<std::mutex> lock(mutex_);
+            std::scoped_lock<std::mutex> lock(mutex_);
             queue_.splice(queue_.end(), tmp);
             if ( queue_.size() == 1 ) {
                 flare_.Fire();
@@ -281,7 +281,7 @@ public:
 
     auto Drain() {
         std::list<broker::event_ptr> events;
-        std::lock_guard<std::mutex> lock(mutex_);
+        std::scoped_lock<std::mutex> lock(mutex_);
         if ( ! queue_.empty() ) {
             queue_.swap(events);
             flare_.Extinguish();
@@ -812,12 +812,10 @@ void Manager::Unpeer(const string& addr, uint16_t port) {
 }
 
 bool Manager::IsOutboundPeering(const string& addr, uint16_t port) const {
-    return bstate->outbound_peerings.find(broker::network_info(addr, port)) != bstate->outbound_peerings.end();
+    return bstate->outbound_peerings.contains(broker::network_info(addr, port));
 }
 
-bool Manager::IsOutboundPeering(const broker::network_info& ni) const {
-    return bstate->outbound_peerings.find(ni) != bstate->outbound_peerings.end();
-}
+bool Manager::IsOutboundPeering(const broker::network_info& ni) const { return bstate->outbound_peerings.contains(ni); }
 
 std::vector<broker::peer_info> Manager::Peers() const {
     if ( bstate->endpoint.is_shutdown() )
@@ -2110,7 +2108,7 @@ const Stats& Manager::GetStatistics() {
 TableValPtr Manager::GetPeeringStatsTable() { return bstate->peerBufferState->GetPeeringStatsTable(); }
 
 bool Manager::AddForwardedStore(const std::string& name, TableValPtr table) {
-    if ( forwarded_stores.find(name) != forwarded_stores.end() ) {
+    if ( forwarded_stores.contains(name) ) {
         reporter->Error("same &broker_store %s specified for two different variables", name.c_str());
         return false;
     }
@@ -2127,7 +2125,7 @@ void Manager::PrepareForwarding(const std::string& name) {
     if ( ! handle )
         return;
 
-    if ( forwarded_stores.find(name) == forwarded_stores.end() )
+    if ( ! forwarded_stores.contains(name) )
         return;
 
     handle->forward_to = forwarded_stores.at(name);
diff --git a/src/broker/data.bif b/src/broker/data.bif
index 0ca117a860..a99c92d8a5 100644
--- a/src/broker/data.bif
+++ b/src/broker/data.bif
@@ -87,7 +87,7 @@ function Broker::__set_contains%(s: Broker::Data, key: any%): bool
 		return zeek::val_mgr->False();
 		}
 
-	return zeek::val_mgr->Bool(v.find(*k) != v.end());
+	return zeek::val_mgr->Bool(v.contains(*k));
 	%}
 
 function Broker::__set_insert%(s: Broker::Data, key: any%): bool
@@ -191,7 +191,7 @@ function Broker::__table_contains%(t: Broker::Data, key: any%): bool
 		return zeek::val_mgr->False();
 		}
 
-	return zeek::val_mgr->Bool(v.find(*k) != v.end());
+	return zeek::val_mgr->Bool(v.contains(*k));
 	%}
 
 function Broker::__table_insert%(t: Broker::Data, key: any, val: any%): Broker::Data
diff --git a/src/cluster/Manager.cc b/src/cluster/Manager.cc
index 29bade62a6..bc43410f9a 100644
--- a/src/cluster/Manager.cc
+++ b/src/cluster/Manager.cc
@@ -46,7 +46,7 @@ std::unique_ptr<LogSerializer> Manager::InstantiateLogSerializer(const zeek::Enu
 bool Manager::ListenWebSocket(const websocket::detail::ServerOptions& options) {
     WebSocketServerKey key{options.host, options.port};
 
-    if ( websocket_servers.count(key) != 0 ) {
+    if ( websocket_servers.contains(key) ) {
         const auto& entry = websocket_servers[key];
         if ( entry.options == options )
             return true;
diff --git a/src/cluster/backend/zeromq/ZeroMQ.cc b/src/cluster/backend/zeromq/ZeroMQ.cc
index 76373b3c64..0a4e9720b0 100644
--- a/src/cluster/backend/zeromq/ZeroMQ.cc
+++ b/src/cluster/backend/zeromq/ZeroMQ.cc
@@ -736,7 +736,7 @@ bool ZeroMQBackend::DoProcessBackendMessage(int tag, byte_buffer_span payload) {
         if ( tag == 1 ) {
             // If this is the first time the subscription was observed, raise
             // the ZeroMQ internal event.
-            if ( xpub_subscriptions.count(topic) == 0 ) {
+            if ( ! xpub_subscriptions.contains(topic) ) {
                 eh = event_subscription;
                 xpub_subscriptions.insert(topic);
             }
diff --git a/src/cluster/websocket/WebSocket.cc b/src/cluster/websocket/WebSocket.cc
index 32142a542b..764978ced2 100644
--- a/src/cluster/websocket/WebSocket.cc
+++ b/src/cluster/websocket/WebSocket.cc
@@ -175,7 +175,7 @@ void WebSocketClient::SetSubscriptions(const std::vector<std::string>& topic_pre
 }
 
 void WebSocketClient::SetSubscriptionActive(const std::string& topic_prefix) {
-    if ( subscriptions_state.count(topic_prefix) == 0 ) {
+    if ( ! subscriptions_state.contains(topic_prefix) ) {
         zeek::reporter->InternalWarning("Unknown topic_prefix for WebSocket client %s!", topic_prefix.c_str());
         return;
     }
diff --git a/src/file_analysis/Manager.cc b/src/file_analysis/Manager.cc
index 43c4abf06d..90363a7f32 100644
--- a/src/file_analysis/Manager.cc
+++ b/src/file_analysis/Manager.cc
@@ -373,7 +373,7 @@ bool Manager::RemoveFile(const string& file_id) {
     return true;
 }
 
-bool Manager::IsIgnored(const string& file_id) { return ignored.find(file_id) != ignored.end(); }
+bool Manager::IsIgnored(const string& file_id) { return ignored.contains(file_id); }
 
 string Manager::GetFileID(const zeek::Tag& tag, Connection* c, bool is_orig) {
     current_file_id.clear();
diff --git a/src/file_analysis/analyzer/x509/X509.cc b/src/file_analysis/analyzer/x509/X509.cc
index 0e60f45789..f80856f3cc 100644
--- a/src/file_analysis/analyzer/x509/X509.cc
+++ b/src/file_analysis/analyzer/x509/X509.cc
@@ -246,7 +246,7 @@ RecordValPtr X509::ParseCertificate(X509Val* cert_val, file_analysis::File* f) {
 
 X509_STORE* X509::GetRootStore(TableVal* root_certs) {
     // If this certificate store was built previously, just reuse the old one.
-    if ( x509_stores.count(root_certs) > 0 )
+    if ( x509_stores.contains(root_certs) )
         return x509_stores[root_certs];
 
     X509_STORE* ctx = X509_STORE_new();
diff --git a/src/iosource/Manager.cc b/src/iosource/Manager.cc
index 96750f7051..fcc67b5ba1 100644
--- a/src/iosource/Manager.cc
+++ b/src/iosource/Manager.cc
@@ -247,13 +247,13 @@ bool Manager::RegisterFd(int fd, IOSource* src, int flags) {
     std::vector<struct kevent> new_events;
 
     if ( (flags & IOSource::READ) != 0 ) {
-        if ( fd_map.count(fd) == 0 ) {
+        if ( ! fd_map.contains(fd) ) {
             new_events.push_back({});
             EV_SET(&(new_events.back()), fd, EVFILT_READ, EV_ADD, 0, 0, nullptr);
         }
     }
     if ( (flags & IOSource::WRITE) != 0 ) {
-        if ( write_fd_map.count(fd) == 0 ) {
+        if ( ! write_fd_map.contains(fd) ) {
             new_events.push_back({});
             EV_SET(&(new_events.back()), fd, EVFILT_WRITE, EV_ADD, 0, 0, nullptr);
         }
@@ -287,13 +287,13 @@ bool Manager::UnregisterFd(int fd, IOSource* src, int flags) {
     std::vector<struct kevent> new_events;
 
     if ( (flags & IOSource::READ) != 0 ) {
-        if ( fd_map.count(fd) != 0 ) {
+        if ( fd_map.contains(fd) ) {
             new_events.push_back({});
             EV_SET(&(new_events.back()), fd, EVFILT_READ, EV_DELETE, 0, 0, nullptr);
         }
     }
     if ( (flags & IOSource::WRITE) != 0 ) {
-        if ( write_fd_map.count(fd) != 0 ) {
+        if ( write_fd_map.contains(fd) ) {
             new_events.push_back({});
             EV_SET(&(new_events.back()), fd, EVFILT_WRITE, EV_DELETE, 0, 0, nullptr);
         }
diff --git a/src/logging/Manager.cc b/src/logging/Manager.cc
index da1ff9d192..0fbb0e9786 100644
--- a/src/logging/Manager.cc
+++ b/src/logging/Manager.cc
@@ -1317,7 +1317,7 @@ bool Manager::DelayFinish(const EnumValPtr& id, const RecordValPtr& record, cons
 // Delaying has completed.
 bool Manager::DelayCompleted(Stream* stream, detail::DelayInfo& delay_info) {
     auto token = detail::to_internal_delay_token(delay_info.TokenVal());
-    assert(stream->delay_tokens.find(token) != stream->delay_tokens.end());
+    assert(stream->delay_tokens.contains(token));
 
     DBG_LOG(DBG_LOGGING, "DelayCompleted() for log record %p RefCnt=%d token=%" PRIu64, delay_info.Record().get(),
             delay_info.Record()->RefCnt(), token);
diff --git a/src/packet_analysis/protocol/ip/IPBasedAnalyzer.cc b/src/packet_analysis/protocol/ip/IPBasedAnalyzer.cc
index 8980f5a7de..8e5be8d60d 100644
--- a/src/packet_analysis/protocol/ip/IPBasedAnalyzer.cc
+++ b/src/packet_analysis/protocol/ip/IPBasedAnalyzer.cc
@@ -155,7 +155,7 @@ bool IPBasedAnalyzer::IsLikelyServerPort(uint32_t port) const {
     // We exploit our knowledge of PortVal's internal storage mechanism here.
     port |= server_port_mask;
 
-    return port_cache.find(port) != port_cache.end();
+    return port_cache.contains(port);
 }
 
 zeek::Connection* IPBasedAnalyzer::NewConn(IPBasedConnKeyPtr key, const Packet* pkt) {
diff --git a/src/plugin/ComponentManager.h b/src/plugin/ComponentManager.h
index 89b9efe976..9c00d977f5 100644
--- a/src/plugin/ComponentManager.h
+++ b/src/plugin/ComponentManager.h
@@ -173,14 +173,14 @@ public:
      *
      * @param tag The component tag to check.
      */
-    auto HasComponentMapping(const zeek::Tag& tag) const { return component_mapping_by_src.count(tag); }
+    bool HasComponentMapping(const zeek::Tag& tag) const { return component_mapping_by_src.contains(tag); }
 
     /**
      * Returns true if a given component is mapped to from a different one.
      *
      * @param tag The component tag to check.
      */
-    bool ProvidesComponentMapping(const zeek::Tag& tag) const { return component_mapping_by_dst.count(tag); }
+    bool ProvidesComponentMapping(const zeek::Tag& tag) const { return component_mapping_by_dst.contains(tag); }
 
 private:
     /** Script layer module in which component tags live. */
diff --git a/src/plugin/Manager.cc b/src/plugin/Manager.cc
index 37aa245778..db78641935 100644
--- a/src/plugin/Manager.cc
+++ b/src/plugin/Manager.cc
@@ -81,7 +81,7 @@ void Manager::SearchDynamicPlugins(const std::string& dir) {
 
     std::string canon_path = canon.string();
 
-    if ( searched_dirs.count(canon_path) )
+    if ( searched_dirs.contains(canon_path) )
         return;
 
     searched_dirs.emplace(canon_path);
diff --git a/src/script_opt/CPP/Compile.h b/src/script_opt/CPP/Compile.h
index 0014081476..13979a2235 100644
--- a/src/script_opt/CPP/Compile.h
+++ b/src/script_opt/CPP/Compile.h
@@ -136,7 +136,7 @@ public:
 
     // Returns true if at least one of the function bodies associated with
     // the function/hook/event handler of the given fname is not compilable.
-    bool NotFullyCompilable(const std::string& fname) const { return not_fully_compilable.count(fname) > 0; }
+    bool NotFullyCompilable(const std::string& fname) const { return not_fully_compilable.contains(fname); }
 
 private:
 #include "zeek/script_opt/CPP/Attrs.h"
diff --git a/src/script_opt/CPP/DeclFunc.cc b/src/script_opt/CPP/DeclFunc.cc
index 3e035da004..d99e194ef2 100644
--- a/src/script_opt/CPP/DeclFunc.cc
+++ b/src/script_opt/CPP/DeclFunc.cc
@@ -31,7 +31,7 @@ void CPPCompile::DeclareLambda(const LambdaExpr* l, const ProfileFunc* pf) {
     auto& ids = l->OuterIDs();
 
     for ( auto lid : ids ) {
-        if ( lambda_names.count(lid) > 0 ) {
+        if ( lambda_names.contains(lid) ) {
             ASSERT(lambda_names[lid] == CaptureName(lid));
         }
         else
@@ -74,7 +74,7 @@ void CPPCompile::CreateFunction(const FuncTypePtr& ft, const ProfileFunc* pf, co
 
     func_index[fname] = cast;
 
-    if ( ! l && casting_index.count(cast) == 0 ) {
+    if ( ! l && ! casting_index.contains(cast) ) {
         casting_index[cast] = func_casting_glue.size();
 
         DispatchInfo di;
@@ -314,7 +314,7 @@ void CPPCompile::GatherParamTypes(vector<string>& p_types, const FuncTypePtr& ft
             // Native types are always pass-by-value.
             p_types.emplace_back(tn);
         else {
-            if ( param_id && pf->Assignees().count(param_id) > 0 )
+            if ( param_id && pf->Assignees().contains(param_id) )
                 // We modify the parameter.
                 p_types.emplace_back(tn);
             else
diff --git a/src/script_opt/CPP/Driver.cc b/src/script_opt/CPP/Driver.cc
index 9e273a83a3..ed41337e6b 100644
--- a/src/script_opt/CPP/Driver.cc
+++ b/src/script_opt/CPP/Driver.cc
@@ -138,7 +138,7 @@ void CPPCompile::Compile(bool report_uncompilable) {
     for ( const auto& l : accessed_lambdas ) {
         const auto& n = l->Name();
         const auto body = l->Ingredients()->Body().get();
-        if ( lambda_ASTs.count(n) > 0 )
+        if ( lambda_ASTs.contains(n) )
             // Reuse previous body.
             body_names[body] = body_names[lambda_ASTs[n]];
         else {
@@ -157,7 +157,7 @@ void CPPCompile::Compile(bool report_uncompilable) {
     lambda_ASTs.clear();
     for ( const auto& l : accessed_lambdas ) {
         const auto& n = l->Name();
-        if ( lambda_ASTs.count(n) > 0 )
+        if ( lambda_ASTs.contains(n) )
             continue;
 
         CompileLambda(l, pfs->ExprProf(l).get());
@@ -196,12 +196,12 @@ bool CPPCompile::AnalyzeFuncBody(FuncInfo& fi, unordered_set<string>& filenames_
     string fn = body->GetLocationInfo()->FileName();
 
     if ( ! analysis_options.allow_cond && ! fi.ShouldSkip() ) {
-        if ( ! analysis_options.only_files.empty() && files_with_conditionals.count(fn) > 0 ) {
+        if ( ! analysis_options.only_files.empty() && files_with_conditionals.contains(fn) ) {
             if ( report_uncompilable )
                 reporter->Warning("%s cannot be compiled to C++ due to source file %s having conditional code",
                                   f->GetName().c_str(), fn.c_str());
 
-            else if ( filenames_reported_as_skipped.count(fn) == 0 ) {
+            else if ( ! filenames_reported_as_skipped.contains(fn) ) {
                 reporter->Warning("skipping compilation of files in %s due to presence of conditional code",
                                   fn.c_str());
                 filenames_reported_as_skipped.emplace(fn);
diff --git a/src/script_opt/CPP/Exprs.cc b/src/script_opt/CPP/Exprs.cc
index d0562d7a7e..20234e8354 100644
--- a/src/script_opt/CPP/Exprs.cc
+++ b/src/script_opt/CPP/Exprs.cc
@@ -148,11 +148,11 @@ string CPPCompile::GenExpr(const Expr* e, GenType gt, bool top_level) {
 string CPPCompile::GenNameExpr(const NameExpr* ne, GenType gt) {
     const auto& t = ne->GetType();
     auto n = ne->Id();
-    bool is_global_var = global_vars.count(n) > 0;
+    bool is_global_var = global_vars.contains(n);
 
     if ( t->Tag() == TYPE_FUNC && ! is_global_var ) {
         auto func = n->Name();
-        if ( globals.count(func) > 0 && pfs->BiFGlobals().count(n) == 0 )
+        if ( globals.contains(func) && ! pfs->BiFGlobals().contains(n) )
             return GenericValPtrToGT(IDNameStr(n), t, gt);
     }
 
@@ -277,8 +277,8 @@ string CPPCompile::GenCallExpr(const CallExpr* c, GenType gt, bool top_level) {
         auto id_name = f_id->Name();
         auto nargs = args_l->Exprs().length();
 
-        bool is_compiled = compiled_simple_funcs.count(id_name) > 0;
-        bool was_compiled = hashed_funcs.count(id_name) > 0;
+        bool is_compiled = compiled_simple_funcs.contains(id_name);
+        bool was_compiled = hashed_funcs.contains(id_name);
         bool is_variadic = params->NumFields() == 1 && nargs != 1;
 
         if ( ! is_async && ! is_variadic && (is_compiled || was_compiled) ) { // Can call directly.
@@ -303,10 +303,10 @@ string CPPCompile::GenCallExpr(const CallExpr* c, GenType gt, bool top_level) {
         //
         // If it is a BiF *that's also a global variable*, then
         // we need to look up the BiF version of the global.
-        if ( pfs->BiFGlobals().count(f_id) == 0 )
+        if ( ! pfs->BiFGlobals().contains(f_id) )
             gen += +"->AsFunc()";
 
-        else if ( accessed_globals.count(f_id) > 0 )
+        else if ( accessed_globals.contains(f_id) )
             // The BiF version has an extra "_", per AddBiF(..., true).
             gen = globals[string(id_name) + "_"];
     }
@@ -1230,7 +1230,7 @@ string CPPCompile::GenField(const ExprPtr& rec, int field) {
     int mapping_slot;
 
     auto rfm = record_field_mappings.find(rt);
-    if ( rfm != record_field_mappings.end() && rfm->second.count(field) > 0 )
+    if ( rfm != record_field_mappings.end() && rfm->second.contains(field) )
         // We're already tracking this field.
         mapping_slot = rfm->second[field];
 
@@ -1269,7 +1269,7 @@ string CPPCompile::GenEnum(const TypePtr& t, const ValPtr& ev) {
     int mapping_slot;
 
     auto evm = enum_val_mappings.find(et);
-    if ( evm != enum_val_mappings.end() && evm->second.count(v) > 0 )
+    if ( evm != enum_val_mappings.end() && evm->second.contains(v) )
         // We're already tracking this value.
         mapping_slot = evm->second[v];
 
diff --git a/src/script_opt/CPP/GenFunc.cc b/src/script_opt/CPP/GenFunc.cc
index 39c1fe60d2..e6307e76de 100644
--- a/src/script_opt/CPP/GenFunc.cc
+++ b/src/script_opt/CPP/GenFunc.cc
@@ -159,11 +159,11 @@ void CPPCompile::DeclareLocals(const ProfileFunc* pf, const IDPList* lambda_ids)
         auto ln = LocalName(l);
         auto cn = CaptureName(l);
 
-        if ( capture_names.count(cn) > 0 )
+        if ( capture_names.contains(cn) )
             // No need to declare these, they're passed in as parameters.
             ln = cn;
 
-        else if ( params.count(l) == 0 && l->Offset() >= num_params ) { // Not a parameter, so must be a local.
+        else if ( ! params.contains(l) && l->Offset() >= num_params ) { // Not a parameter, so must be a local.
             Emit("%s %s;", FullTypeName(l->GetType()), ln);
             did_decl = true;
         }
diff --git a/src/script_opt/CPP/Inits.cc b/src/script_opt/CPP/Inits.cc
index a61630f670..c3358f8e31 100644
--- a/src/script_opt/CPP/Inits.cc
+++ b/src/script_opt/CPP/Inits.cc
@@ -200,7 +200,7 @@ void CPPCompile::InitializeGlobals() {
         if ( ! ofiles.empty() && ! obj_matches_opt_files(g) )
             continue;
 
-        if ( accessed_globals.count(g) == 0 )
+        if ( ! accessed_globals.contains(g) )
             continue;
 
         auto ic = ginit.IC();
@@ -281,7 +281,7 @@ void CPPCompile::GenStandaloneActivation() {
         auto fname = BodyName(func);
         auto bname = Canonicalize(fname) + "_zf";
 
-        if ( compiled_funcs.count(bname) == 0 )
+        if ( ! compiled_funcs.contains(bname) )
             // We didn't wind up compiling it.
             continue;
 
diff --git a/src/script_opt/CPP/RuntimeInitSupport.cc b/src/script_opt/CPP/RuntimeInitSupport.cc
index bf342ce006..0306e53120 100644
--- a/src/script_opt/CPP/RuntimeInitSupport.cc
+++ b/src/script_opt/CPP/RuntimeInitSupport.cc
@@ -82,7 +82,7 @@ void register_lambda__CPP(CPPStmtPtr body, p_hash_type hash, const char* name, T
 }
 
 void register_scripts__CPP(p_hash_type h, void (*callback)()) {
-    ASSERT(standalone_callbacks.count(h) == 0);
+    ASSERT(! standalone_callbacks.contains(h));
     standalone_callbacks[h] = callback;
 }
 
diff --git a/src/script_opt/CPP/Stmts.cc b/src/script_opt/CPP/Stmts.cc
index 61b3cde298..a0b2e1e0c0 100644
--- a/src/script_opt/CPP/Stmts.cc
+++ b/src/script_opt/CPP/Stmts.cc
@@ -82,7 +82,7 @@ void CPPCompile::GenInitStmt(const InitStmt* init) {
         auto type_type = TypeType(t);
         auto type_ind = GenTypeName(t);
 
-        if ( locals.count(aggr.get()) == 0 ) {
+        if ( ! locals.contains(aggr.get()) ) {
             // fprintf(stderr, "aggregate %s unused\n", obj_desc(aggr.get()).c_str());
             continue;
         }
diff --git a/src/script_opt/CPP/Tracker.cc b/src/script_opt/CPP/Tracker.cc
index f3494aa0fc..3e592416b1 100644
--- a/src/script_opt/CPP/Tracker.cc
+++ b/src/script_opt/CPP/Tracker.cc
@@ -15,7 +15,7 @@ void CPPTracker<T>::AddKey(IntrusivePtr<T> key, p_hash_type h) {
     if ( HasKey(key) )
         return;
 
-    if ( map2.count(h) == 0 ) {
+    if ( ! map2.contains(h) ) {
         auto index = keys.size();
         keys.push_back(key);
 
diff --git a/src/script_opt/CPP/Types.cc b/src/script_opt/CPP/Types.cc
index 19fc1b50a5..eb8ccc3f7c 100644
--- a/src/script_opt/CPP/Types.cc
+++ b/src/script_opt/CPP/Types.cc
@@ -73,7 +73,7 @@ string CPPCompile::GenericValPtrToGT(const string& expr, const TypePtr& t, GenTy
 }
 
 string CPPCompile::GenTypeName(const Type* t) {
-    ASSERT(processed_types.count(TypeRep(t)) > 0);
+    ASSERT(processed_types.contains(TypeRep(t)));
     return types.KeyName(TypeRep(t));
 }
 
diff --git a/src/script_opt/CPP/Vars.cc b/src/script_opt/CPP/Vars.cc
index 62888c6ee1..23b0c5fc80 100644
--- a/src/script_opt/CPP/Vars.cc
+++ b/src/script_opt/CPP/Vars.cc
@@ -9,12 +9,12 @@ using namespace std;
 
 void CPPCompile::CreateGlobal(const ID* g) {
     auto gn = string(g->Name());
-    bool is_bif = pfs->BiFGlobals().count(g) > 0;
+    bool is_bif = pfs->BiFGlobals().contains(g);
 
-    if ( accessed_globals.count(g) == 0 ) {
+    if ( ! accessed_globals.contains(g) ) {
         // Only used in the context of calls.  If it's compilable,
         // then we'll call it directly.
-        if ( compilable_funcs.count(gn) > 0 ) {
+        if ( compilable_funcs.contains(gn) ) {
             AddGlobal(gn, "zf");
             return;
         }
@@ -28,7 +28,7 @@ void CPPCompile::CreateGlobal(const ID* g) {
     if ( AddGlobal(gn, "gl") ) { // We'll be creating this global.
         Emit("IDPtr %s;", globals[gn]);
 
-        if ( accessed_events.count(gn) > 0 )
+        if ( accessed_events.contains(gn) )
             // This is an event that's also used as a variable.
             Emit("EventHandlerPtr %s_ev;", globals[gn]);
 
@@ -53,7 +53,7 @@ std::shared_ptr<CPP_InitInfo> CPPCompile::RegisterGlobal(const ID* g) {
 
     auto gn = string(g->Name());
 
-    if ( globals.count(gn) == 0 ) {
+    if ( ! globals.contains(gn) ) {
         // Create a name for it.
         (void)IDNameStr(g);
 
@@ -103,12 +103,12 @@ void CPPCompile::AddBiF(const ID* b, bool is_var) {
     if ( AddGlobal(n, "bif") )
         Emit("Func* %s;", globals[n]);
 
-    ASSERT(BiFs.count(globals[n]) == 0);
+    ASSERT(! BiFs.contains(globals[n]));
     BiFs[globals[n]] = bn;
 }
 
 bool CPPCompile::AddGlobal(const string& g, const char* suffix) {
-    if ( globals.count(g) > 0 )
+    if ( globals.contains(g) )
         return false;
 
     globals.emplace(g, GlobalName(g, suffix));
@@ -120,7 +120,7 @@ void CPPCompile::RegisterEvent(string ev_name) { body_events[body_name].emplace_
 const string& CPPCompile::IDNameStr(const ID* id) {
     if ( id->IsGlobal() ) {
         auto g = string(id->Name());
-        if ( globals.count(g) == 0 )
+        if ( ! globals.contains(g) )
             CreateGlobal(id);
         return globals[g];
     }
diff --git a/src/script_opt/CSE.h b/src/script_opt/CSE.h
index a078f059c6..edbc70b126 100644
--- a/src/script_opt/CSE.h
+++ b/src/script_opt/CSE.h
@@ -26,7 +26,7 @@ public:
     TraversalCode PostExpr(const Expr*) override;
 
     TraversalCode PreType(const Type* t) override {
-        if ( types_seen.count(t) > 0 )
+        if ( types_seen.contains(t) )
             return TC_ABORTSTMT;
         types_seen.insert(t);
         return TC_CONTINUE;
diff --git a/src/script_opt/Expr.cc b/src/script_opt/Expr.cc
index 5a658d8983..2e0be43b46 100644
--- a/src/script_opt/Expr.cc
+++ b/src/script_opt/Expr.cc
@@ -1186,7 +1186,7 @@ bool CmpExpr::IsHasElementsTest() const {
     static std::set<ExprTag> rel_tags = {EXPR_EQ, EXPR_NE, EXPR_LT, EXPR_LE, EXPR_GE, EXPR_GT};
 
     auto t = Tag(); // note, we may invert t below
-    if ( rel_tags.count(t) == 0 )
+    if ( ! rel_tags.contains(t) )
         return false;
 
     auto op1 = GetOp1();
@@ -2396,7 +2396,7 @@ bool LambdaExpr::IsReduced(Reducer* c) const {
     for ( auto& cp : *captures ) {
         auto& cid = cp.Id();
 
-        if ( private_captures.count(cid.get()) == 0 && ! c->ID_IsReduced(cid) )
+        if ( ! private_captures.contains(cid.get()) && ! c->ID_IsReduced(cid) )
             return NonReduced(this);
     }
 
@@ -2424,7 +2424,7 @@ void LambdaExpr::UpdateCaptures(Reducer* c) {
         for ( auto& cp : *captures ) {
             auto& cid = cp.Id();
 
-            if ( private_captures.count(cid.get()) == 0 )
+            if ( ! private_captures.contains(cid.get()) )
                 cp.SetID(c->UpdateID(cid));
         }
 
@@ -2955,7 +2955,7 @@ RecordFieldUpdatesExpr::RecordFieldUpdatesExpr(ExprTag t, const std::vector<cons
 
         // Consistency check that the statement is indeed in the pool,
         // before we remove it.
-        ASSERT(stmt_pool.count(s) > 0);
+        ASSERT(stmt_pool.contains(s));
         stmt_pool.erase(s);
     }
 
diff --git a/src/script_opt/IDOptInfo.cc b/src/script_opt/IDOptInfo.cc
index 026e111b97..8290ec04d6 100644
--- a/src/script_opt/IDOptInfo.cc
+++ b/src/script_opt/IDOptInfo.cc
@@ -216,7 +216,7 @@ void IDOptInfo::BranchBeyond(const Stmt* end_s, const Stmt* block, bool close_al
         printf("ID %s branching forward from %d beyond %d: %s\n", trace_ID, end_s->GetOptInfo()->stmt_num,
                block->GetOptInfo()->stmt_num, obj_desc(end_s).c_str());
 
-    ASSERT(pending_confluences.count(block) > 0);
+    ASSERT(pending_confluences.contains(block));
 
     auto ar = ActiveRegionIndex();
     if ( ar != NO_DEF )
@@ -332,12 +332,12 @@ void IDOptInfo::ConfluenceBlockEndsAfter(const Stmt* s, bool no_orig_flow) {
         if ( ur.EndsAfter() == NO_DEF ) { // End this region.
             ur.SetEndsAfter(stmt_num);
 
-            if ( ur.StartsAfter() <= cs_stmt_num && no_orig_flow && pc.count(i) == 0 )
+            if ( ur.StartsAfter() <= cs_stmt_num && no_orig_flow && ! pc.contains(i) )
                 // Don't include this region in our assessment.
                 continue;
         }
 
-        else if ( ur.EndsAfter() < cs_stmt_num || pc.count(i) == 0 )
+        else if ( ur.EndsAfter() < cs_stmt_num || ! pc.contains(i) )
             // Irrelevant, didn't extend into confluence region.
             // We test here just to avoid the set lookup in
             // the next test, which presumably will sometimes
diff --git a/src/script_opt/Inline.cc b/src/script_opt/Inline.cc
index ebdeb2e5d3..7fef2bb366 100644
--- a/src/script_opt/Inline.cc
+++ b/src/script_opt/Inline.cc
@@ -116,7 +116,7 @@ void Inliner::Analyze() {
                 for ( auto& ccc : call_set[cc] ) {
                     // For each of those, if we don't
                     // already have it, add it.
-                    if ( c.second.count(ccc) > 0 )
+                    if ( c.second.contains(ccc) )
                         // We already have it.
                         continue;
 
@@ -157,7 +157,7 @@ void Inliner::Analyze() {
         if ( func->Flavor() != FUNC_FLAVOR_FUNCTION )
             continue;
 
-        if ( non_recursive_funcs.count(func) == 0 )
+        if ( ! non_recursive_funcs.contains(func) )
             continue;
 
         if ( ! is_ZAM_compilable(f.Profile()) )
@@ -202,7 +202,7 @@ void Inliner::CoalesceEventHandlers() {
 
         if ( func->GetKind() == Func::SCRIPT_FUNC && func->GetBodies().size() > 1 ) {
             ++event_handlers[func];
-            ASSERT(body_to_info.count(body.get()) == 0);
+            ASSERT(! body_to_info.contains(body.get()));
             body_to_info[body.get()] = i;
         }
     }
@@ -420,7 +420,7 @@ ExprPtr Inliner::DoInline(ScriptFuncPtr sf, StmtPtr body, ListExprPtr args, Scop
     for ( int i = 0; i < nparam; ++i ) {
         auto& vi = vars[i];
         params.emplace_back(vi);
-        param_is_modified.emplace_back((pf->Assignees().count(vi.get()) > 0));
+        param_is_modified.emplace_back((pf->Assignees().contains(vi.get())));
     }
 
     // Recursively inline the body.  This is safe to do because we've
diff --git a/src/script_opt/Inline.h b/src/script_opt/Inline.h
index eec0bf49c9..0a77811fcf 100644
--- a/src/script_opt/Inline.h
+++ b/src/script_opt/Inline.h
@@ -30,7 +30,7 @@ public:
     ExprPtr CheckForInlining(CallExprPtr c);
 
     // True if every instance of the function was inlined.
-    bool WasFullyInlined(const Func* f) { return did_inline.count(f) > 0 && skipped_inlining.count(f) == 0; }
+    bool WasFullyInlined(const Func* f) { return did_inline.contains(f) && ! skipped_inlining.contains(f); }
 
 protected:
     // Driver routine that analyzes all of the script functions and
diff --git a/src/script_opt/ObjMgr.h b/src/script_opt/ObjMgr.h
index 07ddec9864..b6589a39ec 100644
--- a/src/script_opt/ObjMgr.h
+++ b/src/script_opt/ObjMgr.h
@@ -41,7 +41,7 @@ private:
 class ObjMgr {
 public:
     void AddObj(const Obj* o) {
-        if ( obj_collection.count(o) == 0 )
+        if ( ! obj_collection.contains(o) )
             obj_collection.emplace(std::pair<const Obj*, ObjWrapper>{o, ObjWrapper(o)});
     }
 
diff --git a/src/script_opt/ProfileFunc.cc b/src/script_opt/ProfileFunc.cc
index e7e432d66f..32cea83801 100644
--- a/src/script_opt/ProfileFunc.cc
+++ b/src/script_opt/ProfileFunc.cc
@@ -52,7 +52,7 @@ ProfileFunc::ProfileFunc(const Func* func, const StmtPtr& body, bool _abs_rec_fi
     num_params = profiled_func_t->Params()->NumFields();
 
     for ( auto l : locals ) {
-        if ( captures.count(l) == 0 && l->Offset() < num_params )
+        if ( ! captures.contains(l) && l->Offset() < num_params )
             params.insert(l);
     }
 }
@@ -470,7 +470,7 @@ TraversalCode ProfileFunc::PreExpr(const Expr* e) {
             // types if needed.
             auto res_type = e->GetType().get();
             auto orig_type = e->GetOp1()->GetType().get();
-            if ( type_aliases.count(res_type) == 0 )
+            if ( ! type_aliases.contains(res_type) )
                 type_aliases[orig_type] = {res_type};
             else
                 type_aliases[orig_type].insert(res_type);
@@ -541,12 +541,12 @@ void ProfileFunc::TrackID(const ID* id) {
 }
 
 void ProfileFunc::TrackAssignment(const ID* id) {
-    if ( assignees.count(id) > 0 )
+    if ( assignees.contains(id) )
         ++assignees[id];
     else
         assignees[id] = 1;
 
-    if ( id->IsGlobal() || captures.count(id) > 0 )
+    if ( id->IsGlobal() || captures.contains(id) )
         non_local_assignees.insert(id);
 }
 
@@ -562,7 +562,7 @@ void ProfileFunc::CheckRecordConstructor(TypePtr t) {
             auto attrs = td->attrs.get();
             constructor_attrs[attrs] = rt;
 
-            if ( rec_constructor_attrs.count(rt.get()) == 0 )
+            if ( ! rec_constructor_attrs.contains(rt.get()) )
                 rec_constructor_attrs[rt.get()] = {attrs};
             else
                 rec_constructor_attrs[rt.get()].insert(attrs);
@@ -735,7 +735,7 @@ void ProfileFuncs::MergeInProfile(ProfileFunc* pf) {
         AnalyzeAttrs(a.first, a.second.get());
 
     for ( auto& ta : pf->TypeAliases() ) {
-        if ( type_aliases.count(ta.first) == 0 )
+        if ( ! type_aliases.contains(ta.first) )
             type_aliases[ta.first] = std::set<const Type*>{};
         type_aliases[ta.first].insert(ta.second.begin(), ta.second.end());
     }
@@ -1294,7 +1294,7 @@ bool ProfileFuncs::AssessSideEffects(const ExprPtr& e, IDSet& non_local_ids, Typ
         // in an attribute context indicates an implicit call.
         return GetCallSideEffects(e->AsNameExpr(), non_local_ids, aggrs, is_unknown);
 
-    ASSERT(expr_profs.count(e.get()) != 0);
+    ASSERT(expr_profs.contains(e.get()));
     auto pf = expr_profs[e.get()];
     return AssessSideEffects(pf.get(), non_local_ids, aggrs, is_unknown);
 }
@@ -1342,7 +1342,7 @@ bool ProfileFuncs::AssessSideEffects(const ProfileFunc* pf, IDSet& non_local_ids
         }
 
         auto pff = func_profs[f];
-        if ( active_func_profiles.count(pff) > 0 )
+        if ( active_func_profiles.contains(pff) )
             // We're already processing this function and arrived here via
             // recursion. Skip further analysis here, we'll do it instead
             // for the original instance.
@@ -1415,7 +1415,7 @@ bool ProfileFuncs::AssessSideEffects(const SideEffectsOp* se, SideEffectsOp::Acc
 }
 
 std::shared_ptr<SideEffectsOp> ProfileFuncs::GetCallSideEffects(const ScriptFunc* sf) {
-    if ( lambda_primaries.count(sf->GetName()) > 0 )
+    if ( lambda_primaries.contains(sf->GetName()) )
         sf = lambda_primaries[sf->GetName()];
 
     auto sf_se = func_side_effects.find(sf);
@@ -1427,7 +1427,7 @@ std::shared_ptr<SideEffectsOp> ProfileFuncs::GetCallSideEffects(const ScriptFunc
     IDSet nla;
     TypeSet mod_aggrs;
 
-    ASSERT(func_profs.count(sf) != 0);
+    ASSERT(func_profs.contains(sf));
     auto pf = func_profs[sf];
     if ( ! AssessSideEffects(pf.get(), nla, mod_aggrs, is_unknown) )
         // Can't figure it out yet.
@@ -1450,7 +1450,7 @@ static std::unordered_map<std::string, std::string> filename_module;
 
 void switch_to_module(const char* module_name) {
     auto loc = GetCurrentLocation();
-    if ( loc.FirstLine() != 0 && filename_module.count(loc.FileName()) == 0 )
+    if ( loc.FirstLine() != 0 && ! filename_module.contains(loc.FileName()) )
         filename_module[loc.FileName()] = module_name;
 }
 
@@ -1542,7 +1542,7 @@ ASTBlockAnalyzer::ASTBlockAnalyzer(std::vector<FuncInfo>& funcs) {
 
 static bool is_compound_stmt(const Stmt* s) {
     static std::set<StmtTag> compound_stmts = {STMT_FOR, STMT_IF, STMT_LIST, STMT_SWITCH, STMT_WHEN, STMT_WHILE};
-    return compound_stmts.count(s->Tag()) > 0;
+    return compound_stmts.contains(s->Tag());
 }
 
 TraversalCode ASTBlockAnalyzer::PreStmt(const Stmt* s) {
@@ -1580,7 +1580,7 @@ std::string ASTBlockAnalyzer::BuildExpandedDescription(const Location* loc) {
     }
 
     auto lk = LocKey(loc);
-    if ( exp_desc.count(lk) == 0 )
+    if ( ! exp_desc.contains(lk) )
         exp_desc[lk] = ls;
 
     return ls;
diff --git a/src/script_opt/ProfileFunc.h b/src/script_opt/ProfileFunc.h
index 9b8b0b90aa..620de87563 100644
--- a/src/script_opt/ProfileFunc.h
+++ b/src/script_opt/ProfileFunc.h
@@ -674,7 +674,7 @@ public:
     // should always be true other than for certain functions with empty
     // bodies that are created post-parsing. Available for debugging so
     // we can assert we have these.
-    bool HaveExpDesc(const Location* loc) const { return exp_desc.count(LocKey(loc)) > 0; }
+    bool HaveExpDesc(const Location* loc) const { return exp_desc.contains(LocKey(loc)); }
 
 private:
     // Construct the full expanded description associated with the given
diff --git a/src/script_opt/Reduce.cc b/src/script_opt/Reduce.cc
index 44afdafd4a..d15dac1b40 100644
--- a/src/script_opt/Reduce.cc
+++ b/src/script_opt/Reduce.cc
@@ -327,7 +327,7 @@ bool Reducer::ID_IsReducedOrTopLevel(const ID* id) {
 }
 
 bool Reducer::ID_IsReduced(const ID* id) const {
-    return inline_block_level == 0 || tracked_ids.count(id) > 0 || id->IsGlobal() || IsTemporary(id);
+    return inline_block_level == 0 || tracked_ids.contains(id) || id->IsGlobal() || IsTemporary(id);
 }
 
 StmtPtr Reducer::GenParam(const IDPtr& id, ExprPtr rhs, bool is_modified) {
@@ -335,7 +335,7 @@ StmtPtr Reducer::GenParam(const IDPtr& id, ExprPtr rhs, bool is_modified) {
     param->SetLocationInfo(rhs->GetLocationInfo());
     auto rhs_id = rhs->Tag() == EXPR_NAME ? rhs->AsNameExpr()->IdPtr() : nullptr;
 
-    if ( rhs_id && pf->Locals().count(rhs_id.get()) == 0 && ! rhs_id->IsConst() )
+    if ( rhs_id && ! pf->Locals().contains(rhs_id.get()) && ! rhs_id->IsConst() )
         // It's hard to guarantee the RHS won't change during
         // the inline block's execution.
         is_modified = true;
@@ -838,14 +838,14 @@ IDPtr Reducer::GenLocal(const IDPtr& orig) {
         local_id->GetOptInfo()->SetTemp();
 
     IDPtr prev;
-    if ( orig_to_new_locals.count(orig.get()) )
+    if ( orig_to_new_locals.contains(orig.get()) )
         prev = orig_to_new_locals[orig.get()];
 
     AddNewLocal(local_id);
     om.AddObj(orig.get());
     orig_to_new_locals[orig.get()] = local_id;
 
-    if ( ! block_locals.empty() && ret_vars.count(orig.get()) == 0 )
+    if ( ! block_locals.empty() && ! ret_vars.contains(orig.get()) )
         block_locals.back()[orig.get()] = prev;
 
     return local_id;
@@ -853,7 +853,7 @@ IDPtr Reducer::GenLocal(const IDPtr& orig) {
 
 bool Reducer::IsNewLocal(const ID* id) const {
     ID* non_const_ID = (ID*)id; // I don't get why C++ requires this
-    return new_locals.count(non_const_ID) != 0;
+    return new_locals.contains(non_const_ID);
 }
 
 std::shared_ptr<TempVar> Reducer::FindTemporary(const ID* id) const {
diff --git a/src/script_opt/Reduce.h b/src/script_opt/Reduce.h
index b69e4e0229..f3a6f26f25 100644
--- a/src/script_opt/Reduce.h
+++ b/src/script_opt/Reduce.h
@@ -83,9 +83,9 @@ public:
     bool IsNewLocal(const ID* id) const;
 
     bool IsTemporary(const ID* id) const { return FindTemporary(id) != nullptr; }
-    bool IsParamTemp(const ID* id) const { return param_temps.count(id) > 0; }
+    bool IsParamTemp(const ID* id) const { return param_temps.contains(id); }
 
-    bool IsConstantVar(const ID* id) const { return constant_vars.find(id) != constant_vars.end(); }
+    bool IsConstantVar(const ID* id) const { return constant_vars.contains(id); }
 
     // True if the Reducer is being used in the context of a second
     // pass over for AST optimization.
@@ -97,7 +97,7 @@ public:
 
     // A predicate that returns true if the given statement should
     // be removed due to AST optimization.
-    bool ShouldOmitStmt(const Stmt* s) const { return omitted_stmts.find(s) != omitted_stmts.end(); }
+    bool ShouldOmitStmt(const Stmt* s) const { return omitted_stmts.contains(s); }
 
     // Provides a replacement for the given statement due to
     // AST optimization, or nil if there's no replacement.
diff --git a/src/script_opt/ScriptOpt.cc b/src/script_opt/ScriptOpt.cc
index 8e6db2f1c5..b13649b488 100644
--- a/src/script_opt/ScriptOpt.cc
+++ b/src/script_opt/ScriptOpt.cc
@@ -52,9 +52,9 @@ void analyze_lambda(LambdaExpr* l) {
 
 void analyze_when_lambda(LambdaExpr* l) { when_lambdas.insert(l->PrimaryFunc().get()); }
 
-bool is_lambda(const ScriptFunc* f) { return lambdas.count(f) > 0; }
+bool is_lambda(const ScriptFunc* f) { return lambdas.contains(f); }
 
-bool is_when_lambda(const ScriptFunc* f) { return when_lambdas.count(f) > 0; }
+bool is_when_lambda(const ScriptFunc* f) { return when_lambdas.contains(f); }
 
 void analyze_global_stmts(Stmt* stmts) {
     if ( analysis_options.gen_standalone_CPP && obj_matches_opt_files(stmts) )
@@ -396,7 +396,7 @@ static void report_CPP() {
         }
 
         auto hash = f.Profile()->HashVal();
-        bool have = compiled_scripts.count(hash) > 0;
+        bool have = compiled_scripts.contains(hash);
 
         printf("script function %s (hash %llu): %s\n", name.c_str(), hash, have ? "yes" : "no");
 
@@ -408,7 +408,7 @@ static void report_CPP() {
 
     int addl = 0;
     for ( const auto& s : compiled_scripts )
-        if ( already_reported.count(s.first) == 0 ) {
+        if ( ! already_reported.contains(s.first) ) {
             printf("%s body (hash %llu)\n", s.second.body->Name().c_str(), s.first);
             ++addl;
         }
@@ -441,7 +441,7 @@ static void use_CPP() {
             // we're using code compiled for standalone.
             if ( f.Body()->Tag() != STMT_CPP ) {
                 auto func = f.Func();
-                if ( added_bodies[func->GetName()].count(hash) > 0 )
+                if ( added_bodies[func->GetName()].contains(hash) )
                     // We've already added the
                     // replacement.  Delete orig.
                     func->ReplaceBody(f.Body(), nullptr);
@@ -535,7 +535,7 @@ static void analyze_scripts_for_ZAM(std::shared_ptr<ProfileFuncs> pfs) {
         bool is_lambda = l != lambdas.end();
 
         if ( ! analysis_options.compile_all && ! is_lambda && inl && inl->WasFullyInlined(func.get()) &&
-             func_used_indirectly.count(func.get()) == 0 ) {
+             ! func_used_indirectly.contains(func.get()) ) {
             // No need to compile as it won't be called directly.  We'd
             // like to zero out the body to recover the memory, but a *few*
             // such functions do get called, such as by the event engine
@@ -732,7 +732,7 @@ bool has_AST_node_unknown_to_script_opt(const ProfileFunc* prof, bool /* is_ZAM
     static_assert(NUM_STMTS == SCRIPT_OPT_NUM_STMTS);
 
     for ( auto& s : prof->Stmts() )
-        if ( known_stmts.count(s->Tag()) == 0 )
+        if ( ! known_stmts.contains(s->Tag()) )
             return true;
 
     // clang-format off
@@ -821,7 +821,7 @@ bool has_AST_node_unknown_to_script_opt(const ProfileFunc* prof, bool /* is_ZAM
     static_assert(NUM_EXPRS == SCRIPT_OPT_NUM_EXPRS);
 
     for ( auto& e : prof->Exprs() )
-        if ( known_exprs.count(e->Tag()) == 0 )
+        if ( ! known_exprs.contains(e->Tag()) )
             return true;
 
     return false;
diff --git a/src/script_opt/Stmt.cc b/src/script_opt/Stmt.cc
index 62acce3441..80240e18b4 100644
--- a/src/script_opt/Stmt.cc
+++ b/src/script_opt/Stmt.cc
@@ -771,7 +771,7 @@ static unsigned int find_rec_assignment_chain(const std::vector<StmtPtr>& stmts,
             return i;
 
         auto lhs_field = lhs->AsFieldExpr()->Field();
-        if ( fields_seen.count(lhs_field) > 0 )
+        if ( fields_seen.contains(lhs_field) )
             // Earlier in this chain we've already seen "x$a", so end the
             // chain at this repeated use because it's no longer a simple
             // block of field assignments.
@@ -925,7 +925,7 @@ static bool simplify_chain(const std::vector<StmtPtr>& stmts, unsigned int start
 
     // At this point, chain_stmts has only the remainders that weren't removed.
     for ( auto s : stmts )
-        if ( chain_stmts.count(s.get()) > 0 )
+        if ( chain_stmts.contains(s.get()) )
             f_stmts.push_back(std::move(s));
 
     return true;
@@ -1106,7 +1106,7 @@ bool WhenInfo::HasUnreducedIDs(Reducer* c) const {
     for ( auto& cp : *cl ) {
         const auto& cid = cp.Id();
 
-        if ( when_new_locals.count(cid.get()) == 0 && ! c->ID_IsReduced(cp.Id()) )
+        if ( ! when_new_locals.contains(cid.get()) && ! c->ID_IsReduced(cp.Id()) )
             return true;
     }
 
@@ -1120,7 +1120,7 @@ bool WhenInfo::HasUnreducedIDs(Reducer* c) const {
 void WhenInfo::UpdateIDs(Reducer* c) {
     for ( auto& cp : *cl ) {
         auto& cid = cp.Id();
-        if ( when_new_locals.count(cid.get()) == 0 )
+        if ( ! when_new_locals.contains(cid.get()) )
             cp.SetID(c->UpdateID(cid));
     }
 
diff --git a/src/script_opt/UsageAnalyzer.cc b/src/script_opt/UsageAnalyzer.cc
index 4ebc11f387..0961b45b24 100644
--- a/src/script_opt/UsageAnalyzer.cc
+++ b/src/script_opt/UsageAnalyzer.cc
@@ -49,7 +49,7 @@ UsageAnalyzer::UsageAnalyzer(std::vector<FuncInfo>& funcs) {
         if ( t->AsFuncType()->Flavor() == FUNC_FLAVOR_FUNCTION )
             continue;
 
-        if ( reachables.count(id) > 0 )
+        if ( reachables.contains(id) )
             continue;
 
         auto flavor = t->AsFuncType()->FlavorString();
@@ -69,7 +69,7 @@ UsageAnalyzer::UsageAnalyzer(std::vector<FuncInfo>& funcs) {
     for ( auto& gpair : globals ) {
         auto& id = gpair.second;
 
-        if ( reachables.count(id.get()) > 0 )
+        if ( reachables.contains(id.get()) )
             continue;
 
         auto f = GetFuncIfAny(id);
@@ -109,7 +109,7 @@ public:
     }
 
     TraversalCode PreType(const Type* t) override {
-        if ( analyzed_types.count(t) > 0 )
+        if ( analyzed_types.contains(t) )
             return TC_ABORTSTMT;
 
         analyzed_types.insert(t);
@@ -117,7 +117,7 @@ public:
     }
 
     TraversalCode PreID(const ID* id) override {
-        if ( ids.count(id) > 0 )
+        if ( ids.contains(id) )
             return TC_ABORTSTMT;
 
         if ( attr_depth > 0 )
@@ -149,7 +149,7 @@ void UsageAnalyzer::FindSeeds(IDSet& seeds) const {
         auto f = GetFuncIfAny(id);
 
         if ( f && id->GetType<FuncType>()->Flavor() == FUNC_FLAVOR_EVENT ) {
-            if ( script_events.count(f->GetName()) == 0 )
+            if ( ! script_events.contains(f->GetName()) )
                 seeds.insert(id.get());
 
             continue;
@@ -225,7 +225,7 @@ void UsageAnalyzer::Expand(const ID* id) {
 }
 
 TraversalCode UsageAnalyzer::PreID(const ID* id) {
-    if ( analyzed_IDs.count(id) > 0 )
+    if ( analyzed_IDs.contains(id) )
         // No need to repeat the analysis.
         return TC_ABORTSTMT;
 
@@ -234,7 +234,7 @@ TraversalCode UsageAnalyzer::PreID(const ID* id) {
 
     auto f = GetFuncIfAny(id);
 
-    if ( f && reachables.count(id) == 0 )
+    if ( f && ! reachables.contains(id) )
         // Haven't seen this function before.
         new_reachables.insert(id);
 
@@ -254,7 +254,7 @@ TraversalCode UsageAnalyzer::PreID(const ID* id) {
 }
 
 TraversalCode UsageAnalyzer::PreType(const Type* t) {
-    if ( analyzed_types.count(t) > 0 )
+    if ( analyzed_types.contains(t) )
         return TC_ABORTSTMT;
 
     // Save processing by avoiding a re-traversal of this type.
diff --git a/src/script_opt/UseDefs.cc b/src/script_opt/UseDefs.cc
index 07e249a47e..8657c5be80 100644
--- a/src/script_opt/UseDefs.cc
+++ b/src/script_opt/UseDefs.cc
@@ -49,7 +49,7 @@ void UseDefs::Dump() {
     for ( int i = stmts.size(); --i >= 0; ) {
         const auto& s = stmts[i];
         auto uds = FindUsage(s);
-        auto are_copies = (UDs_are_copies.find(s) != UDs_are_copies.end());
+        auto are_copies = (UDs_are_copies.contains(s));
 
         printf("UDs (%s) for %s:\n", are_copies ? "copy" : "orig", obj_desc(s).c_str());
 
@@ -186,7 +186,7 @@ UDs UseDefs::PropagateUDs(const Stmt* s, UDs succ_UDs, const Stmt* succ_stmt, bo
 
                 if ( i == int(stmts.size()) - 1 ) { // Very last statement.
                     succ = succ_stmt;
-                    if ( successor2.find(s) != successor2.end() ) {
+                    if ( successor2.contains(s) ) {
                         om.AddObj(s_i);
                         successor2[s_i] = successor2[s];
                     }
@@ -620,7 +620,7 @@ void UseDefs::FoldInUDs(UDs& main_UDs, const UDs& u1, const UDs& u2) {
 void UseDefs::UpdateUDs(const Stmt* s, const UDs& uds) {
     auto curr_uds = FindUsage(s);
 
-    if ( ! curr_uds || UDs_are_copies.find(s) != UDs_are_copies.end() ) {
+    if ( ! curr_uds || UDs_are_copies.contains(s) ) {
         // Copy-on-write.
         auto new_uds = std::make_shared<UseDefSet>();
 
diff --git a/src/script_opt/UseDefs.h b/src/script_opt/UseDefs.h
index ff9ef9ffc9..0b77c7bf6a 100644
--- a/src/script_opt/UseDefs.h
+++ b/src/script_opt/UseDefs.h
@@ -27,7 +27,7 @@ public:
 
     void Replicate(const UDs& from) { use_defs = from->use_defs; }
 
-    bool HasID(const ID* id) { return use_defs.find(id) != use_defs.end(); }
+    bool HasID(const ID* id) { return use_defs.contains(id); }
 
     void Add(const ID* id) { use_defs.insert(id); }
     void Remove(const ID* id) { use_defs.erase(id); }
@@ -56,8 +56,8 @@ public:
     void Analyze();
 
     // True if we've computed use-defs for the given statement.
-    bool HasUsage(const Stmt* s) const { return use_defs_map.find(s) != use_defs_map.end(); }
     bool HasUsage(const StmtPtr& s) const { return HasUsage(s.get()); }
+    bool HasUsage(const Stmt* s) const { return use_defs_map.contains(s); }
 
     // Returns the use-defs for the given statement.
     UDs GetUsage(const Stmt* s) const { return FindUsage(s); }
diff --git a/src/script_opt/ZAM/AM-Opt.cc b/src/script_opt/ZAM/AM-Opt.cc
index fc8ceb9cfb..4f7059cf94 100644
--- a/src/script_opt/ZAM/AM-Opt.cc
+++ b/src/script_opt/ZAM/AM-Opt.cc
@@ -43,10 +43,10 @@ void finalize_functions(const std::vector<FuncInfo>& funcs) {
     for ( auto& f : funcs ) {
         auto func = f.Func();
 
-        if ( leave_alone.count(func) > 0 )
+        if ( leave_alone.contains(func) )
             continue;
 
-        if ( remapped_intrp_frame_sizes.count(func) == 0 )
+        if ( ! remapped_intrp_frame_sizes.contains(func) )
             // No entry for this function, keep current frame size.
             continue;
 
@@ -282,7 +282,7 @@ bool ZAMCompiler::PruneUnused() {
             continue;
 
         int slot = inst->v1;
-        if ( denizen_ending.count(slot) > 0 )
+        if ( denizen_ending.contains(slot) )
             // Variable is used, keep assignment.
             continue;
 
@@ -306,7 +306,7 @@ bool ZAMCompiler::PruneUnused() {
         // can't remove the instruction entirely because it has
         // side effects.  Transform the instruction into its flavor
         // that doesn't make an assignment.
-        if ( assignmentless_op.count(inst->op) == 0 )
+        if ( ! assignmentless_op.contains(inst->op) )
             reporter->InternalError("inconsistency in re-flavoring instruction with side effects");
 
         inst->op_type = assignmentless_op_class[inst->op];
@@ -506,14 +506,14 @@ void ZAMCompiler::ReMapFrame() {
     for ( zeek_uint_t i = 0; i < insts1.size(); ++i ) {
         auto inst = insts1[i];
 
-        if ( inst_beginnings.count(inst) == 0 )
+        if ( ! inst_beginnings.contains(inst) )
             continue;
 
         auto vars = inst_beginnings[inst];
         for ( auto v : vars ) {
             // Don't remap variables whose values aren't actually used.
             int slot = frame_layout1[v];
-            if ( denizen_ending.count(slot) > 0 )
+            if ( denizen_ending.contains(slot) )
                 ReMapVar(v, slot, i);
         }
     }
@@ -667,7 +667,7 @@ void ZAMCompiler::ReMapInterpreterFrame() {
     // Update frame sizes for functions that might have more than
     // one body.
     auto f = func.get();
-    if ( remapped_intrp_frame_sizes.count(f) == 0 || remapped_intrp_frame_sizes[f] < next_interp_slot )
+    if ( ! remapped_intrp_frame_sizes.contains(f) || remapped_intrp_frame_sizes[f] < next_interp_slot )
         remapped_intrp_frame_sizes[f] = next_interp_slot;
 }
 
@@ -753,7 +753,7 @@ void ZAMCompiler::CheckSlotAssignment(int slot, const ZInstI* inst) {
 }
 
 void ZAMCompiler::SetLifetimeStart(int slot, const ZInstI* inst) {
-    if ( denizen_beginning.count(slot) > 0 ) {
+    if ( denizen_beginning.contains(slot) ) {
         // Beginning of denizen's lifetime already seen, nothing
         // more to do other than check for consistency.
         ASSERT(denizen_beginning[slot]->inst_num <= inst->inst_num);
@@ -762,7 +762,7 @@ void ZAMCompiler::SetLifetimeStart(int slot, const ZInstI* inst) {
     else { // denizen begins here
         denizen_beginning[slot] = inst;
 
-        if ( inst_beginnings.count(inst) == 0 )
+        if ( ! inst_beginnings.contains(inst) )
             // Need to create a set to track the denizens
             // beginning at the instruction.
             inst_beginnings[inst] = {};
@@ -777,7 +777,7 @@ void ZAMCompiler::CheckSlotUse(int slot, const ZInstI* inst) {
 
     ASSERT(static_cast<zeek_uint_t>(slot) < frame_denizens.size());
 
-    if ( denizen_beginning.count(slot) == 0 ) {
+    if ( ! denizen_beginning.contains(slot) ) {
         ODesc d;
         inst->loc->Loc()->Describe(&d);
         reporter->Error("%s: value used but not set: %s", d.Description(), frame_denizens[slot]->Name());
@@ -788,7 +788,7 @@ void ZAMCompiler::CheckSlotUse(int slot, const ZInstI* inst) {
     // at a lower loop depth than that for this instruction, then we
     // extend its lifetime to the end of this instruction's loop.
     if ( reducer->IsTemporary(frame_denizens[slot]) ) {
-        ASSERT(denizen_beginning.count(slot) > 0);
+        ASSERT(denizen_beginning.contains(slot));
         int definition_depth = denizen_beginning[slot]->loop_depth;
 
         if ( inst->loop_depth > definition_depth )
@@ -805,7 +805,7 @@ void ZAMCompiler::ExtendLifetime(int slot, const ZInstI* inst) {
     auto id = frame_denizens[slot];
     auto& t = id->GetType();
 
-    if ( denizen_ending.count(slot) > 0 ) {
+    if ( denizen_ending.contains(slot) ) {
         // End of denizen's lifetime already seen.  Check for
         // consistency and then extend as needed.
 
@@ -828,7 +828,7 @@ void ZAMCompiler::ExtendLifetime(int slot, const ZInstI* inst) {
         if ( old_inst->inst_num < inst->inst_num ) { // Extend.
             inst_endings[old_inst].erase(frame_denizens[slot]);
 
-            if ( inst_endings.count(inst) == 0 )
+            if ( ! inst_endings.contains(inst) )
                 inst_endings[inst] = {};
 
             inst_endings[inst].insert(frame_denizens[slot]);
@@ -839,7 +839,7 @@ void ZAMCompiler::ExtendLifetime(int slot, const ZInstI* inst) {
     else { // first time seeing a use of this denizen
         denizen_ending[slot] = inst;
 
-        if ( inst_endings.count(inst) == 0 ) {
+        if ( ! inst_endings.contains(inst) ) {
             IDSet denizens;
             inst_endings[inst] = denizens;
         }
@@ -988,9 +988,9 @@ void ZAMCompiler::KillInst(zeek_uint_t i) {
     if ( inst->aux && ! inst->aux->cft.empty() ) {
         auto& cft = inst->aux->cft;
 
-        if ( cft.count(CFT_ELSE) > 0 ) {
+        if ( cft.contains(CFT_ELSE) ) {
             // Push forward unless this was the end of the block.
-            if ( cft.count(CFT_BLOCK_END) == 0 ) {
+            if ( ! cft.contains(CFT_BLOCK_END) ) {
                 ASSERT(succ);
                 AddCFT(succ, CFT_ELSE);
             }
@@ -1007,15 +1007,15 @@ void ZAMCompiler::KillInst(zeek_uint_t i) {
         // because they just lead to their following instruction, and next's
         // if they become dead code. However, loops and loop conditionals
         // should not be killed.
-        ASSERT(cft.count(CFT_LOOP) == 0);
-        ASSERT(cft.count(CFT_LOOP_COND) == 0);
+        ASSERT(! cft.contains(CFT_LOOP));
+        ASSERT(! cft.contains(CFT_LOOP_COND));
     }
 }
 
 void ZAMCompiler::BackPropagateCFT(int inst_num, ControlFlowType cf_type) {
     auto inst = insts1[inst_num];
     auto& cft = inst->aux->cft;
-    if ( cft.count(cf_type) == 0 )
+    if ( ! cft.contains(cf_type) )
         return;
 
     int j = inst_num;
diff --git a/src/script_opt/ZAM/Driver.cc b/src/script_opt/ZAM/Driver.cc
index 1970021a8a..88460d03a4 100644
--- a/src/script_opt/ZAM/Driver.cc
+++ b/src/script_opt/ZAM/Driver.cc
@@ -43,7 +43,7 @@ void ZAMCompiler::Init() {
 
     TrackMemoryManagement();
 
-    non_recursive = non_recursive_funcs.count(func.get()) > 0;
+    non_recursive = non_recursive_funcs.contains(func.get());
 }
 
 void ZAMCompiler::InitGlobals() {
@@ -92,7 +92,7 @@ void ZAMCompiler::InitLocals() {
         if ( IsCapture(l) )
             continue;
 
-        if ( pf->WhenLocals().count(l) > 0 )
+        if ( pf->WhenLocals().contains(l) )
             continue;
 
         auto non_const_l = const_cast<ID*>(l);
diff --git a/src/script_opt/ZAM/Expr.cc b/src/script_opt/ZAM/Expr.cc
index 3e5a2faac9..68027c2926 100644
--- a/src/script_opt/ZAM/Expr.cc
+++ b/src/script_opt/ZAM/Expr.cc
@@ -322,7 +322,7 @@ const ZAMStmt ZAMCompiler::CompileRecFieldUpdates(const RecordFieldUpdatesExpr*
     bool homogeneous = field_tags.size() == 1;
     // Here we leverage the fact that C++ "+=" works identically for
     // signed and unsigned int's.
-    if ( ! homogeneous && field_tags.size() == 2 && field_tags.count(TYPE_INT) > 0 && field_tags.count(TYPE_COUNT) > 0 )
+    if ( ! homogeneous && field_tags.size() == 2 && field_tags.contains(TYPE_INT) && field_tags.contains(TYPE_COUNT) )
         homogeneous = true;
 
     ZOp op;
@@ -338,7 +338,7 @@ const ZAMStmt ZAMCompiler::CompileRecFieldUpdates(const RecordFieldUpdatesExpr*
     }
 
     else if ( homogeneous ) {
-        if ( field_tags.count(TYPE_DOUBLE) > 0 )
+        if ( field_tags.contains(TYPE_DOUBLE) )
             op = OP_REC_ADD_DOUBLE_FIELDS_VV;
         else
             // Here we leverage that += will work for both signed/unsigned.
@@ -951,7 +951,7 @@ const ZAMStmt ZAMCompiler::BuildLambda(int n_slot, ExprPtr e) {
     for ( int i = 0; i < ncaptures; ++i ) {
         auto& id_i = (*captures)[i].Id();
 
-        if ( pf->WhenLocals().count(id_i.get()) > 0 )
+        if ( pf->WhenLocals().contains(id_i.get()) )
             aux->Add(i, nullptr);
         else
             aux->Add(i, FrameSlot(id_i), id_i->GetType());
diff --git a/src/script_opt/ZAM/OPs/stmts.op b/src/script_opt/ZAM/OPs/stmts.op
index 7572d63155..760e147b22 100644
--- a/src/script_opt/ZAM/OPs/stmts.op
+++ b/src/script_opt/ZAM/OPs/stmts.op
@@ -118,7 +118,7 @@ eval	static auto any_val = ZVal();
 macro EvalSwitchBody(index, branch, cases, postscript)
 	{
 	auto t = cases[index];
-	if ( t.find(v) == t.end() )
+	if ( ! t.contains(v) )
 		pc = branch;
 	else
 		pc = t[v];
diff --git a/src/script_opt/ZAM/Validate.cc b/src/script_opt/ZAM/Validate.cc
index 6f2cd042eb..f90280c09c 100644
--- a/src/script_opt/ZAM/Validate.cc
+++ b/src/script_opt/ZAM/Validate.cc
@@ -102,7 +102,7 @@ void validate_ZAM_insts() {
 
     for ( int i = 0; i < int(OP_NOP); ++i ) {
         auto zop = ZOp(i);
-        if ( zam_inst_desc.find(zop) == zam_inst_desc.end() && assignment_flavor.find(zop) == assignment_flavor.end() )
+        if ( ! zam_inst_desc.contains(zop) && ! assignment_flavor.contains(zop) )
             reporter->InternalError("op %s missing from description", ZOP_name(zop));
     }
 
diff --git a/src/script_opt/ZAM/Vars.cc b/src/script_opt/ZAM/Vars.cc
index 3d1ef0c781..a396f3c940 100644
--- a/src/script_opt/ZAM/Vars.cc
+++ b/src/script_opt/ZAM/Vars.cc
@@ -22,7 +22,7 @@ bool ZAMCompiler::IsUnused(const IDPtr& id, const Stmt* where) const {
 
 bool ZAMCompiler::IsCapture(const ID* id) const {
     const auto& c = pf->CapturesOffsets();
-    return c.find(id) != c.end();
+    return c.contains(id);
 }
 
 int ZAMCompiler::CaptureOffset(const ID* id) const {
@@ -143,7 +143,7 @@ int ZAMCompiler::RawSlot(const ID* id) {
     return id_slot->second;
 }
 
-bool ZAMCompiler::HasFrameSlot(const ID* id) const { return frame_layout1.find(id) != frame_layout1.end(); }
+bool ZAMCompiler::HasFrameSlot(const ID* id) const { return frame_layout1.contains(id); }
 
 int ZAMCompiler::NewSlot(bool is_managed) {
     char buf[8192];
diff --git a/src/script_opt/ZAM/ZInst.cc b/src/script_opt/ZAM/ZInst.cc
index b9bfe5c451..939c10b47c 100644
--- a/src/script_opt/ZAM/ZInst.cc
+++ b/src/script_opt/ZAM/ZInst.cc
@@ -653,7 +653,7 @@ bool ZInstI::IsGlobalLoad() const {
         }
     }
 
-    return global_ops.count(op) > 0;
+    return global_ops.contains(op);
 }
 
 bool ZInstI::IsCaptureLoad() const { return op == OP_LOAD_CAPTURE_Vi || op == OP_LOAD_MANAGED_CAPTURE_Vi; }
diff --git a/src/script_opt/ZAM/ZOp.cc b/src/script_opt/ZAM/ZOp.cc
index 904ebe6940..628f1c503b 100644
--- a/src/script_opt/ZAM/ZOp.cc
+++ b/src/script_opt/ZAM/ZOp.cc
@@ -83,7 +83,7 @@ ZOp AssignmentFlavor(ZOp orig, TypeTag tag, bool strict) {
         default: break;
     }
 
-    if ( assignment_flavor.count(orig) == 0 ) {
+    if ( ! assignment_flavor.contains(orig) ) {
         if ( strict )
             ASSERT(false);
         else
@@ -92,7 +92,7 @@ ZOp AssignmentFlavor(ZOp orig, TypeTag tag, bool strict) {
 
     auto orig_map = assignment_flavor[orig];
 
-    if ( orig_map.count(tag) == 0 ) {
+    if ( ! orig_map.contains(tag) ) {
         if ( strict )
             ASSERT(false);
         else
diff --git a/src/strings.bif b/src/strings.bif
index d9728bb938..cc239c0075 100644
--- a/src/strings.bif
+++ b/src/strings.bif
@@ -1251,7 +1251,7 @@ function hexdump%(data_str: string%) : string
 function reverse%(str: string%) : string
 	%{
 	string s = str->ToStdString();
-	reverse(s.begin(), s.end());
+	std::ranges::reverse(s);
 	return zeek::make_intrusive<zeek::StringVal>(s.length(), (const char*)s.c_str());
 	%}
 
@@ -1308,8 +1308,8 @@ static int64_t do_find_str(zeek::StringVal* str, zeek::StringVal* sub, int64_t s
 
 	if ( ! case_sensitive )
 		{
-		transform(s.begin(), s.end(), s.begin(), ::tolower);
-		transform(sb.begin(), sb.end(), sb.begin(), ::tolower);
+		std::ranges::transform(s, s.begin(), ::tolower);
+		std::ranges::transform(sb, sb.begin(), ::tolower);
 		}
 
 	if ( rfind )
diff --git a/src/supervisor/Supervisor.cc b/src/supervisor/Supervisor.cc
index 665efd1bb8..48894d1f0e 100644
--- a/src/supervisor/Supervisor.cc
+++ b/src/supervisor/Supervisor.cc
@@ -1071,7 +1071,7 @@ std::optional<SupervisedNode> Stem::Poll() {
 
         if ( cmd == "create" ) {
             const auto& node_json = msg_tokens[2];
-            assert(nodes.find(node_name) == nodes.end());
+            assert(! nodes.contains(node_name));
             auto node_config = Supervisor::NodeConfig::FromJSON(node_json);
             auto it = nodes.emplace(node_name, std::move(node_config)).first;
             auto& node = it->second;
@@ -1514,7 +1514,7 @@ std::string Supervisor::Create(const Supervisor::NodeConfig& node) {
     if ( node.name.find(' ') != std::string::npos )
         return util::fmt("node names must not contain spaces: '%s'", node.name.data());
 
-    if ( nodes.find(node.name) != nodes.end() )
+    if ( nodes.contains(node.name) )
         return util::fmt("node with name '%s' already exists", node.name.data());
 
     if ( node.interface.has_value() && node.pcap_file.has_value() )
diff --git a/src/telemetry/telemetry_functions.bif b/src/telemetry/telemetry_functions.bif
index 8672e864bb..95bbd9331a 100644
--- a/src/telemetry/telemetry_functions.bif
+++ b/src/telemetry/telemetry_functions.bif
@@ -73,7 +73,7 @@ bool labels_valid(std::span<const zeek::telemetry::LabelView> labels,
 		return std::find(keys.begin(), keys.end(), x.first) != keys.end();
 		};
 	return labels.size() == label_names.size()
-	       && std::all_of(labels.begin(), labels.end(), key_in_label_names);
+	       && std::ranges::all_of(labels, key_in_label_names);
 	}
 
 template <class IntOrDbl>
diff --git a/src/zeek-setup.cc b/src/zeek-setup.cc
index 9b1253bf88..070aad5308 100644
--- a/src/zeek-setup.cc
+++ b/src/zeek-setup.cc
@@ -275,11 +275,11 @@ static bool show_plugins(int level) {
 
     int count = 0;
 
-    for ( plugin::Manager::plugin_list::const_iterator i = plugins.begin(); i != plugins.end(); i++ ) {
-        if ( requested_plugins.size() && requested_plugins.find((*i)->Name()) == requested_plugins.end() )
+    for ( const auto& plugin : plugins ) {
+        if ( ! requested_plugins.empty() && ! requested_plugins.contains(plugin->Name()) )
             continue;
 
-        (*i)->Describe(&d);
+        plugin->Describe(&d);
 
         if ( ! d.IsShort() )
             d.Add("\n");
diff --git a/src/zeek.bif b/src/zeek.bif
index a70d5f11f1..961ebca1ee 100644
--- a/src/zeek.bif
+++ b/src/zeek.bif
@@ -9,13 +9,14 @@
 
 %%{ // C++ segment
 #include <sys/stat.h>
-#include <string>
 #include <algorithm>
 #include <cinttypes>
 #include <cmath>
 #include <cstdio>
 #include <cstring>
 #include <ctime>
+#include <numbers>
+#include <string>
 #include <vector>
 
 #include "zeek/digest.h"
@@ -4222,7 +4223,7 @@ function blocking_lookup_hostname%(host: string%) : addr_set
 ## .. zeek:see:: haversine_distance_ip
 function haversine_distance%(lat1: double, long1: double, lat2: double, long2: double%): double
 	%{
-	const double PI = 3.14159;
+	const double PI = std::numbers::pi;
 	const double RADIUS = 3958.8;  // Earth's radius in miles.
 
 	double s1 = sin((lat2 - lat1) * PI/360);
diff --git a/src/zeekygen/Target.cc b/src/zeekygen/Target.cc
index f0a8e35f92..364e4db6ba 100644
--- a/src/zeekygen/Target.cc
+++ b/src/zeekygen/Target.cc
@@ -494,7 +494,7 @@ void ScriptTarget::DoGenerate() const {
         }
 
         for ( const auto& f : dir_contents ) {
-            if ( targets.find(f) != targets.end() )
+            if ( targets.contains(f) )
                 continue;
 
             if ( unlink(f.c_str()) < 0 )
diff --git a/testing/btest/Baseline/bifs.haversine_distance/out b/testing/btest/Baseline/bifs.haversine_distance/out
index 280113f884..50022c3d80 100644
--- a/testing/btest/Baseline/bifs.haversine_distance/out
+++ b/testing/btest/Baseline/bifs.haversine_distance/out
@@ -3,6 +3,6 @@
 5.8481e+03
 1.9193e-02
 1.5136e-02
-9.2419e-01
+9.0763e-01
 1.2437e+04
 1.2437e+04
diff --git a/tools/binpac/src/pac_type.cc b/tools/binpac/src/pac_type.cc
index 0488c6f8cc..354fc3cc16 100644
--- a/tools/binpac/src/pac_type.cc
+++ b/tools/binpac/src/pac_type.cc
@@ -912,7 +912,7 @@ Type* Type::LookUpByID(ID* id) {
 }
 
 void Type::AddPredefinedType(const string& type_name, Type* type) {
-    ASSERT(type_map_.find(type_name) == type_map_.end());
+    ASSERT(! type_map_.contains(type_name));
     type_map_[type_name] = type;
 }