From 884ce6abb5a3bfeec6390e6420dc9042e1e6617d Mon Sep 17 00:00:00 2001
From: Andreas Buhr <andreas@andreasbuhr.de>
Date: Wed, 10 Dec 2025 16:29:10 +0100
Subject: [PATCH 1/8] pass end iterator by const-ref

---
 include/boost/parser/parser.hpp | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/include/boost/parser/parser.hpp b/include/boost/parser/parser.hpp
index 1c5585f3..d332e2ae 100644
--- a/include/boost/parser/parser.hpp
+++ b/include/boost/parser/parser.hpp
@@ -2425,7 +2425,7 @@ namespace boost { namespace parser {
             typename ErrorHandler>
         bool parse_impl(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Parser const & parser,
             ErrorHandler const & error_handler,
             Attr & attr)
@@ -2478,7 +2478,7 @@ namespace boost { namespace parser {
             typename ErrorHandler>
         auto parse_impl(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Parser const & parser,
             ErrorHandler const & error_handler)
         {
@@ -2534,7 +2534,7 @@ namespace boost { namespace parser {
             typename Callbacks>
         bool callback_parse_impl(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Parser const & parser,
             ErrorHandler const & error_handler,
             Callbacks const & callbacks)
@@ -2589,7 +2589,7 @@ namespace boost { namespace parser {
             typename ErrorHandler>
         bool skip_parse_impl(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Parser const & parser,
             SkipParser const & skip,
             ErrorHandler const & error_handler,
@@ -2639,7 +2639,7 @@ namespace boost { namespace parser {
             typename ErrorHandler>
         auto skip_parse_impl(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Parser const & parser,
             SkipParser const & skip,
             ErrorHandler const & error_handler)
@@ -2694,7 +2694,7 @@ namespace boost { namespace parser {
             typename Callbacks>
         bool callback_skip_parse_impl(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Parser const & parser,
             SkipParser const & skip,
             ErrorHandler const & error_handler,
@@ -2844,7 +2844,7 @@ namespace boost { namespace parser {
         T if_full_parse(
             I initial_first,
             I & first,
-            S last,
+            S const & last,
             ErrorHandler const & error_handler,
             T retval)
         {
@@ -9155,7 +9155,7 @@ namespace boost { namespace parser {
 #endif
     bool prefix_parse(
         I & first,
-        S last,
+        S const & last,
         parser_interface<Parser, GlobalState, ErrorHandler> const & parser,
         Attr & attr,
         trace trace_mode = trace::off)
@@ -9294,7 +9294,7 @@ namespace boost { namespace parser {
 #endif
     auto prefix_parse(
         I & first,
-        S last,
+        S const & last,
         parser_interface<Parser, GlobalState, ErrorHandler> const & parser,
         trace trace_mode = trace::off)
     {
@@ -9405,7 +9405,7 @@ namespace boost { namespace parser {
 #endif
     bool prefix_parse(
         I & first,
-        S last,
+        S const & last,
         parser_interface<Parser, GlobalState, ErrorHandler> const & parser,
         parser_interface<SkipParser> const & skip,
         Attr & attr,
@@ -9547,7 +9547,7 @@ namespace boost { namespace parser {
 #endif
     auto prefix_parse(
         I & first,
-        S last,
+        S const & last,
         parser_interface<Parser, GlobalState, ErrorHandler> const & parser,
         parser_interface<SkipParser> const & skip,
         trace trace_mode = trace::off)
@@ -9664,7 +9664,7 @@ namespace boost { namespace parser {
 #endif
     bool callback_prefix_parse(
         I & first,
-        S last,
+        S const & last,
         parser_interface<Parser, GlobalState, ErrorHandler> const & parser,
         Callbacks const & callbacks,
         trace trace_mode = trace::off)
@@ -9790,7 +9790,7 @@ namespace boost { namespace parser {
 #endif
     bool callback_prefix_parse(
         I & first,
-        S last,
+        S const & last,
         parser_interface<Parser, GlobalState, ErrorHandler> const & parser,
         parser_interface<SkipParser> const & skip,
         Callbacks const & callbacks,

From cf92ba1f79e394529823886be195049dafa3baee Mon Sep 17 00:00:00 2001
From: Andreas Buhr <andreas@andreasbuhr.de>
Date: Wed, 10 Dec 2025 16:49:56 +0100
Subject: [PATCH 2/8] pass end iterator by const-ref

---
 include/boost/parser/parser.hpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/boost/parser/parser.hpp b/include/boost/parser/parser.hpp
index d332e2ae..41ddac73 100644
--- a/include/boost/parser/parser.hpp
+++ b/include/boost/parser/parser.hpp
@@ -456,7 +456,7 @@ namespace boost { namespace parser {
             static constexpr bool use_callbacks = UseCallbacks;
 
             I first_;
-            S last_;
+            S const & last_;
             bool * pass_ = nullptr;
             int * trace_indent_ = nullptr;
             symbol_table_tries_t * symbol_table_tries_ = nullptr;
@@ -525,7 +525,7 @@ namespace boost { namespace parser {
                 std::bool_constant<DoTrace>,
                 std::bool_constant<UseCallbacks>,
                 I & first,
-                S last,
+                S const & last,
                 bool & success,
                 int & indent,
                 ErrorHandler const & error_handler,
@@ -548,7 +548,7 @@ namespace boost { namespace parser {
                 std::bool_constant<DoTrace>,
                 std::bool_constant<UseCallbacks>,
                 I & first,
-                S last,
+                S const & last,
                 bool & success,
                 int & indent,
                 ErrorHandler const & error_handler,
@@ -566,7 +566,7 @@ namespace boost { namespace parser {
                 std::bool_constant<DoTrace>,
                 std::bool_constant<UseCallbacks>,
                 I & first,
-                S last,
+                S const & last,
                 bool & success,
                 int & indent,
                 ErrorHandler const & error_handler,

From e65b31fa0df44a35c25c6f31caf47c63f5441126 Mon Sep 17 00:00:00 2001
From: Andreas Buhr <andreas@andreasbuhr.de>
Date: Wed, 10 Dec 2025 17:07:14 +0100
Subject: [PATCH 3/8] pass end iterator by const-ref

---
 include/boost/parser/parser.hpp     | 50 ++++++++++++++---------------
 include/boost/parser/parser_fwd.hpp |  2 +-
 2 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/include/boost/parser/parser.hpp b/include/boost/parser/parser.hpp
index 41ddac73..6e026806 100644
--- a/include/boost/parser/parser.hpp
+++ b/include/boost/parser/parser.hpp
@@ -852,7 +852,7 @@ namespace boost { namespace parser {
             typename ErrorHandler>
         auto make_context(
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             bool & success,
             int & indent,
             ErrorHandler const & error_handler,
@@ -882,7 +882,7 @@ namespace boost { namespace parser {
             typename ErrorHandler>
         auto make_context(
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             bool & success,
             int & indent,
             ErrorHandler const & error_handler,
@@ -910,7 +910,7 @@ namespace boost { namespace parser {
             typename GlobalState>
         auto make_context(
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             bool & success,
             int & indent,
             ErrorHandler const & error_handler,
@@ -941,7 +941,7 @@ namespace boost { namespace parser {
             typename Callbacks>
         auto make_context(
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             bool & success,
             int & indent,
             ErrorHandler const & error_handler,
@@ -975,7 +975,7 @@ namespace boost { namespace parser {
             typename GlobalState>
         auto make_context(
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             bool & success,
             int & indent,
             ErrorHandler const & error_handler,
@@ -1520,7 +1520,7 @@ namespace boost { namespace parser {
         inline void append(nope &, nope &&, bool) {}
 
         template<typename Container, typename Iter, typename Sentinel>
-        void append(Container & c, Iter first, Sentinel last, bool gen_attrs)
+        void append(Container & c, Iter first, Sentinel const & last, bool gen_attrs)
         {
             if (!gen_attrs)
                 return;
@@ -1539,7 +1539,7 @@ namespace boost { namespace parser {
         void append(
             std::optional<Container> & c,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             bool gen_attrs)
         {
             if (!gen_attrs)
@@ -1550,7 +1550,7 @@ namespace boost { namespace parser {
         }
 
         template<typename Iter, typename Sentinel>
-        void append(nope &, Iter first, Sentinel last, bool gen_attrs)
+        void append(nope &, Iter first, Sentinel const & last, bool gen_attrs)
         {}
 
         constexpr inline flags default_flags()
@@ -1639,12 +1639,12 @@ namespace boost { namespace parser {
 
         template<typename Iter, typename Sentinel>
         void
-        skip(Iter & first, Sentinel last, null_parser const & skip_, flags f)
+        skip(Iter & first, Sentinel const & last, null_parser const & skip_, flags f)
         {}
 
         template<typename Iter, typename Sentinel, typename SkipParser>
         void
-        skip(Iter & first, Sentinel last, SkipParser const & skip_, flags f)
+        skip(Iter & first, Sentinel const & last, SkipParser const & skip_, flags f)
         {
             if (!detail::use_skip(f))
                 return;
@@ -1953,7 +1953,7 @@ namespace boost { namespace parser {
         };
 
         template<bool SortedUTF32, typename Iter, typename Sentinel>
-        constexpr auto make_char_range(Iter first, Sentinel last)
+        constexpr auto make_char_range(Iter first, Sentinel const & last)
         {
             return char_range<Iter, Sentinel, SortedUTF32>{
                 BOOST_PARSER_SUBRANGE<Iter, Sentinel>{first, last}};
@@ -2279,7 +2279,7 @@ namespace boost { namespace parser {
         void apply_parser(
             Parser const & parser,
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             flags flags,
@@ -3425,7 +3425,7 @@ namespace boost { namespace parser {
             }
 
             Iter & first_;
-            Sentinel last_;
+            Sentinel const & last_;
             Context const & context_;
             SkipParser const & skip_;
             detail::flags flags_;
@@ -3441,7 +3441,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -3506,7 +3506,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -3609,7 +3609,7 @@ namespace boost { namespace parser {
             }
 
             Iter & first_;
-            Sentinel last_;
+            Sentinel const & last_;
             Context const & context_;
             SkipParser const & skip_;
             detail::flags flags_;
@@ -3625,7 +3625,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first_,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -3670,7 +3670,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first_,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4229,7 +4229,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto make_temp_result(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4298,7 +4298,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first_,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4358,7 +4358,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first_,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4476,7 +4476,7 @@ namespace boost { namespace parser {
             typename Merged>
         void call_impl(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4493,7 +4493,7 @@ namespace boost { namespace parser {
                 "");
 
             auto use_parser = [&first,
-                               last,
+                               &last,
                                &context,
                                &skip,
                                flags_ = flags,
@@ -9964,7 +9964,7 @@ namespace boost { namespace parser {
 
             using context = decltype(detail::make_context<false, false>(
                 std::declval<iterator>(),
-                std::declval<sentinel>(),
+                std::declval<sentinel&>(),
                 std::declval<bool &>(),
                 std::declval<int &>(),
                 std::declval<error_handler_type>(),
@@ -9973,7 +9973,7 @@ namespace boost { namespace parser {
                 std::declval<detail::pending_symbol_table_operations_t &>()));
             using type = decltype(std::declval<Parser>()(
                 std::declval<iterator &>(),
-                std::declval<sentinel>(),
+                std::declval<sentinel&>(),
                 std::declval<context>(),
                 SkipParser{},
                 detail::flags::gen_attrs,
diff --git a/include/boost/parser/parser_fwd.hpp b/include/boost/parser/parser_fwd.hpp
index 44565e88..b475cce3 100644
--- a/include/boost/parser/parser_fwd.hpp
+++ b/include/boost/parser/parser_fwd.hpp
@@ -111,7 +111,7 @@ namespace boost { namespace parser {
             typename ErrorHandler>
         inline auto make_context(
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             bool & success,
             int & indent,
             ErrorHandler const & error_handler,

From 4e65d97d787f2b7f88f23b3446da51bf859b5b44 Mon Sep 17 00:00:00 2001
From: Andreas Buhr <andreas@andreasbuhr.de>
Date: Wed, 10 Dec 2025 17:22:33 +0100
Subject: [PATCH 4/8] pass end iterator by const-ref

---
 include/boost/parser/parser.hpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/boost/parser/parser.hpp b/include/boost/parser/parser.hpp
index 6e026806..fb525a02 100644
--- a/include/boost/parser/parser.hpp
+++ b/include/boost/parser/parser.hpp
@@ -3152,7 +3152,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -3173,7 +3173,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -3316,7 +3316,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -3339,7 +3339,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,

From 256b07359e837ed3af988b384a1e4395fb9c51a8 Mon Sep 17 00:00:00 2001
From: Andreas Buhr <andreas@andreasbuhr.de>
Date: Wed, 10 Dec 2025 17:26:47 +0100
Subject: [PATCH 5/8] pass end iterator by const-ref

---
 include/boost/parser/parser.hpp | 132 ++++++++++++++++----------------
 1 file changed, 66 insertions(+), 66 deletions(-)

diff --git a/include/boost/parser/parser.hpp b/include/boost/parser/parser.hpp
index fb525a02..3e8e55c3 100644
--- a/include/boost/parser/parser.hpp
+++ b/include/boost/parser/parser.hpp
@@ -1611,7 +1611,7 @@ namespace boost { namespace parser {
                 typename SkipParser>
             nope operator()(
                 Iter & first,
-                Sentinel last,
+                Sentinel const & last,
                 Context const & context,
                 SkipParser const & skip,
                 flags flags,
@@ -1628,7 +1628,7 @@ namespace boost { namespace parser {
                 typename Attribute>
             void operator()(
                 Iter & first,
-                Sentinel last,
+                Sentinel const & last,
                 Context const & context,
                 SkipParser const & skip,
                 flags flags,
@@ -2312,7 +2312,7 @@ namespace boost { namespace parser {
         void apply_parser(
             Parser const & parser,
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             flags flags,
@@ -2334,7 +2334,7 @@ namespace boost { namespace parser {
         void apply_parser(
             Parser const & parser,
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             flags flags,
@@ -2356,7 +2356,7 @@ namespace boost { namespace parser {
         void apply_parser(
             Parser const & parser,
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             flags flags,
@@ -2371,7 +2371,7 @@ namespace boost { namespace parser {
         // API implementations
 
         template<typename Iter, typename Sentinel, typename Parser>
-        auto has_attribute(Iter first, Sentinel last, Parser parser);
+        auto has_attribute(Iter first, Sentinel const & last, Parser parser);
 
         template<typename BaseIter, typename Iter>
         struct scoped_base_assign
@@ -3775,7 +3775,7 @@ namespace boost { namespace parser {
             int... Is>
         void call_impl(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -3871,7 +3871,7 @@ namespace boost { namespace parser {
         {
             dummy_use_parser_t(
                 Iter & first,
-                Sentinel last,
+                Sentinel const & last,
                 Context const & context,
                 SkipParser const & skip,
                 detail::flags flags,
@@ -3895,7 +3895,7 @@ namespace boost { namespace parser {
                     success_);
             }
             Iter & first_;
-            Sentinel last_;
+            Sentinel const & last_;
             Context const & context_;
             SkipParser const & skip_;
             detail::flags flags_;
@@ -4695,7 +4695,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         detail::nope call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4714,7 +4714,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4783,7 +4783,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4809,7 +4809,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4841,7 +4841,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         detail::nope call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4870,7 +4870,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4904,7 +4904,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         BOOST_PARSER_SUBRANGE<Iter> call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4923,7 +4923,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4962,7 +4962,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -4990,7 +4990,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -5047,7 +5047,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -5068,7 +5068,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -5103,7 +5103,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context_,
             SkipParser const & skip,
             detail::flags flags,
@@ -5127,7 +5127,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context_,
             SkipParser const & skip,
             detail::flags flags,
@@ -5158,7 +5158,7 @@ namespace boost { namespace parser {
             typename SkipParser_>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser_ const & skip,
             detail::flags flags,
@@ -5179,7 +5179,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser_ const & skip,
             detail::flags flags,
@@ -5226,7 +5226,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         detail::nope call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -5245,7 +5245,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -5395,7 +5395,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         T call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -5414,7 +5414,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -5480,7 +5480,7 @@ namespace boost { namespace parser {
             attr_type>
         call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -5581,7 +5581,7 @@ namespace boost { namespace parser {
             typename Attribute_>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -5991,7 +5991,7 @@ namespace boost { namespace parser {
             typename SkipParserType>
         auto operator()(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParserType const & skip,
             detail::flags flags,
@@ -6010,7 +6010,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void operator()(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParserType const & skip,
             detail::flags flags,
@@ -6324,7 +6324,7 @@ namespace boost { namespace parser {
     decltype(rule_name_)::parser_type::attr_type parse_rule(                   \
         decltype(rule_name_)::parser_type::tag_type *,                         \
         Iter & first,                                                          \
-        Sentinel last,                                                         \
+        Sentinel const & last,                                                         \
         Context const & context,                                               \
         SkipParser const & skip,                                               \
         boost::parser::detail::flags flags,                                    \
@@ -6360,7 +6360,7 @@ namespace boost { namespace parser {
     void parse_rule(                                                           \
         decltype(rule_name_)::parser_type::tag_type *,                         \
         Iter & first,                                                          \
-        Sentinel last,                                                         \
+        Sentinel const & last,                                                         \
         Context const & context,                                               \
         SkipParser const & skip,                                               \
         boost::parser::detail::flags flags,                                    \
@@ -6816,7 +6816,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         detail::nope call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -6845,7 +6845,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -6899,7 +6899,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         detail::nope call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -6922,7 +6922,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -6955,7 +6955,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const &,
             detail::flags flags,
@@ -6976,7 +6976,7 @@ namespace boost { namespace parser {
             typename Attribute_>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7025,7 +7025,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7044,7 +7044,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7192,7 +7192,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7211,7 +7211,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7345,7 +7345,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7364,7 +7364,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7427,7 +7427,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7446,7 +7446,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7551,7 +7551,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         std::string call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7570,7 +7570,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7717,7 +7717,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         std::string call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -7736,7 +7736,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8040,7 +8040,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         detail::nope call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8059,7 +8059,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8209,7 +8209,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         bool call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8228,7 +8228,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8300,7 +8300,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         T call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8319,7 +8319,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8443,7 +8443,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         T call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8462,7 +8462,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8560,7 +8560,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         T call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8579,7 +8579,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8668,7 +8668,7 @@ namespace boost { namespace parser {
             typename SkipParser>
         auto call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -8698,7 +8698,7 @@ namespace boost { namespace parser {
             typename Attribute>
         void call(
             Iter & first,
-            Sentinel last,
+            Sentinel const & last,
             Context const & context,
             SkipParser const & skip,
             detail::flags flags,
@@ -9981,7 +9981,7 @@ namespace boost { namespace parser {
         };
 
         template<typename Iter, typename Sentinel, typename Parser>
-        auto has_attribute(Iter first, Sentinel last, Parser parser)
+        auto has_attribute(Iter first, Sentinel const & last, Parser parser)
         {
             using attr_t = typename attribute_impl<
                 BOOST_PARSER_SUBRANGE<Iter, Sentinel>,

From 678ea490ada26470f52d6c970abdc99dc3970487 Mon Sep 17 00:00:00 2001
From: Andreas Buhr <andreas@andreasbuhr.de>
Date: Wed, 10 Dec 2025 17:34:57 +0100
Subject: [PATCH 6/8] pass end iterator by const-ref

---
 .../boost/parser/detail/text/algorithm.hpp    | 33 ++++++++++---------
 .../detail/text/transcode_algorithm.hpp       | 26 +++++++--------
 2 files changed, 31 insertions(+), 28 deletions(-)

diff --git a/include/boost/parser/detail/text/algorithm.hpp b/include/boost/parser/detail/text/algorithm.hpp
index 9f22affb..09660a52 100644
--- a/include/boost/parser/detail/text/algorithm.hpp
+++ b/include/boost/parser/detail/text/algorithm.hpp
@@ -21,13 +21,13 @@ namespace boost::parser::detail { namespace text {
 
     namespace detail {
         template<typename Iter>
-        std::ptrdiff_t distance(Iter first, Iter last, non_sentinel_tag)
+        std::ptrdiff_t distance(Iter first, Iter const & last, non_sentinel_tag)
         {
             return std::distance(first, last);
         }
 
         template<typename Iter, typename Sentinel>
-        std::ptrdiff_t distance(Iter first, Sentinel last, sentinel_tag)
+        std::ptrdiff_t distance(Iter first, Sentinel const & last, sentinel_tag)
         {
             std::ptrdiff_t retval = 0;
             while (first != last) {
@@ -41,7 +41,7 @@ namespace boost::parser::detail { namespace text {
     /** Range-friendly version of `std::distance()`, taking an iterator and a
         sentinel. */
     template<typename Iter, typename Sentinel>
-    std::ptrdiff_t distance(Iter first, Sentinel last)
+    std::ptrdiff_t distance(Iter first, Sentinel const & last)
     {
         return detail::distance(
             first,
@@ -55,7 +55,7 @@ namespace boost::parser::detail { namespace text {
     /** Range-friendly version of `std::find()`, taking an iterator and a
         sentinel. */
     template<typename BidiIter, typename Sentinel, typename T>
-    BidiIter find(BidiIter first, Sentinel last, T const & x)
+    BidiIter find(BidiIter first, Sentinel const & last, T const & x)
     {
         while (first != last) {
             if (*first == x)
@@ -68,7 +68,7 @@ namespace boost::parser::detail { namespace text {
     /** A range-friendly compliment to `std::find()`; returns an iterator to
         the first element not equal to `x`. */
     template<typename BidiIter, typename Sentinel, typename T>
-    BidiIter find_not(BidiIter first, Sentinel last, T const & x)
+    BidiIter find_not(BidiIter first, Sentinel const & last, T const & x)
     {
         while (first != last) {
             if (*first != x)
@@ -81,7 +81,7 @@ namespace boost::parser::detail { namespace text {
     /** Range-friendly version of `std::find_if()`, taking an iterator and a
         sentinel. */
     template<typename BidiIter, typename Sentinel, typename Pred>
-    BidiIter find_if(BidiIter first, Sentinel last, Pred p)
+    BidiIter find_if(BidiIter first, Sentinel const & last, Pred p)
     {
         while (first != last) {
             if (p(*first))
@@ -94,7 +94,7 @@ namespace boost::parser::detail { namespace text {
     /** Range-friendly version of `std::find_if_not()`, taking an iterator and
         a sentinel. */
     template<typename BidiIter, typename Sentinel, typename Pred>
-    BidiIter find_if_not(BidiIter first, Sentinel last, Pred p)
+    BidiIter find_if_not(BidiIter first, Sentinel const & last, Pred p)
     {
         while (first != last) {
             if (!p(*first))
@@ -166,7 +166,7 @@ namespace boost::parser::detail { namespace text {
         the first element of the subsequence.  Subranges passed to `f` are
         non-overlapping. */
     template<typename FwdIter, typename Sentinel, typename Func>
-    Func foreach_subrange(FwdIter first, Sentinel last, Func f)
+    Func foreach_subrange(FwdIter first, Sentinel const & last, Func f)
     {
         while (first != last) {
             auto const & x = *first;
@@ -185,7 +185,7 @@ namespace boost::parser::detail { namespace text {
         `proj(e)` each compares equal to `proj()` of the first element of the
         subsequence.  Subranges passed to `f` are non-overlapping. */
     template<typename FwdIter, typename Sentinel, typename Func, typename Proj>
-    Func foreach_subrange(FwdIter first, Sentinel last, Func f, Proj proj)
+    Func foreach_subrange(FwdIter first, Sentinel const & last, Func f, Proj proj)
     {
         using value_type = typename std::iterator_traits<FwdIter>::value_type;
         while (first != last) {
@@ -207,7 +207,7 @@ namespace boost::parser::detail { namespace text {
         is a contiguous subsequence of elements, each of which is equal to
         `x`.  Subranges passed to `f` are non-overlapping. */
     template<typename FwdIter, typename Sentinel, typename T, typename Func>
-    Func foreach_subrange_of(FwdIter first, Sentinel last, T const & x, Func f)
+    Func foreach_subrange_of(FwdIter first, Sentinel const & last, T const & x, Func f)
     {
         while (first != last) {
             first = boost::parser::detail::text::find(first, last, x);
@@ -225,7 +225,7 @@ namespace boost::parser::detail { namespace text {
         is a contiguous subsequence of elements `ei` for which `p(ei)` is
         true.  Subranges passed to `f` are non-overlapping. */
     template<typename FwdIter, typename Sentinel, typename Pred, typename Func>
-    Func foreach_subrange_if(FwdIter first, Sentinel last, Pred p, Func f)
+    Func foreach_subrange_if(FwdIter first, Sentinel const & last, Pred p, Func f)
     {
         while (first != last) {
             first = boost::parser::detail::text::find_if(first, last, p);
@@ -241,7 +241,7 @@ namespace boost::parser::detail { namespace text {
 
     /** Sentinel-friendly version of `std::all_of()`. */
     template<typename Iter, typename Sentinel, typename Pred>
-    bool all_of(Iter first, Sentinel last, Pred p)
+    bool all_of(Iter first, Sentinel const & last, Pred p)
     {
         for (; first != last; ++first) {
             if (!p(*first))
@@ -256,7 +256,7 @@ namespace boost::parser::detail { namespace text {
         typename Sentinel1,
         typename Iter2,
         typename Sentinel2>
-    bool equal(Iter1 first1, Sentinel1 last1, Iter2 first2, Sentinel2 last2)
+    bool equal(Iter1 first1, Sentinel1 const & last1, Iter2 first2, Sentinel2 const & last2)
     {
         for (; first1 != last1 && first2 != last2; ++first1, ++first2) {
             if (*first1 != *first2)
@@ -272,7 +272,7 @@ namespace boost::parser::detail { namespace text {
         typename Iter2,
         typename Sentinel2>
     std::pair<Iter1, Iter2>
-    mismatch(Iter1 first1, Sentinel1 last1, Iter2 first2, Sentinel2 last2)
+    mismatch(Iter1 first1, Sentinel1 const & last1, Iter2 first2, Sentinel2 const & last2)
     {
         for (; first1 != last1 && first2 != last2; ++first1, ++first2) {
             if (*first1 != *first2)
@@ -290,7 +290,10 @@ namespace boost::parser::detail { namespace text {
         typename Iter2,
         typename Sentinel2>
     int lexicographical_compare_three_way(
-        Iter1 first1, Sentinel1 last1, Iter2 first2, Sentinel2 last2)
+        Iter1 first1,
+        Sentinel1 const & last1,
+        Iter2 first2,
+        Sentinel2 const & last2)
     {
         auto const iters = boost::parser::detail::text::mismatch(first1, last1, first2, last2);
         if (iters.first == last1) {
diff --git a/include/boost/parser/detail/text/transcode_algorithm.hpp b/include/boost/parser/detail/text/transcode_algorithm.hpp
index a8b869c0..b65276be 100644
--- a/include/boost/parser/detail/text/transcode_algorithm.hpp
+++ b/include/boost/parser/detail/text/transcode_algorithm.hpp
@@ -81,7 +81,7 @@ namespace boost::parser::detail { namespace text {
             typename OutIter>
         transcode_result<InputIter, OutIter> transcode_utf_8_to_16(
             InputIter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out,
             std::input_iterator_tag)
@@ -103,7 +103,7 @@ namespace boost::parser::detail { namespace text {
         template<bool UseN, typename Iter, typename OutIter>
         transcode_result<Iter, OutIter> transcode_utf_8_to_16(
             Iter first,
-            Iter last,
+            Iter const & last,
             std::ptrdiff_t n,
             OutIter out,
             std::random_access_iterator_tag)
@@ -119,7 +119,7 @@ namespace boost::parser::detail { namespace text {
             typename OutIter>
         transcode_result<InputIter, OutIter> transcode_utf_8_to_32(
             InputIter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out,
             std::input_iterator_tag)
@@ -141,7 +141,7 @@ namespace boost::parser::detail { namespace text {
         template<bool UseN, typename Iter, typename OutIter>
         transcode_result<Iter, OutIter> transcode_utf_8_to_32(
             Iter first,
-            Iter last,
+            Iter const & last,
             std::ptrdiff_t n,
             OutIter out,
             std::random_access_iterator_tag)
@@ -158,7 +158,7 @@ namespace boost::parser::detail { namespace text {
         transcode_result<Iter, OutIter> transcode_to_8(
             tag_t<format::utf8>,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out)
         {
@@ -173,7 +173,7 @@ namespace boost::parser::detail { namespace text {
         transcode_result<Iter, OutIter> transcode_to_16(
             tag_t<format::utf8>,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out)
         {
@@ -189,7 +189,7 @@ namespace boost::parser::detail { namespace text {
         transcode_result<Iter, OutIter> transcode_to_32(
             tag_t<format::utf8>,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out)
         {
@@ -205,7 +205,7 @@ namespace boost::parser::detail { namespace text {
         transcode_result<Iter, OutIter> transcode_to_8(
             tag_t<format::utf16>,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out)
         {
@@ -247,7 +247,7 @@ namespace boost::parser::detail { namespace text {
         transcode_result<Iter, OutIter> transcode_to_16(
             tag_t<format::utf16>,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out)
         {
@@ -261,7 +261,7 @@ namespace boost::parser::detail { namespace text {
         transcode_result<Iter, OutIter> transcode_to_32(
             tag_t<format::utf16>,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out)
         {
@@ -304,7 +304,7 @@ namespace boost::parser::detail { namespace text {
         transcode_result<Iter, OutIter> transcode_to_8(
             tag_t<format::utf32>,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out)
         {
@@ -318,7 +318,7 @@ namespace boost::parser::detail { namespace text {
         transcode_result<Iter, OutIter> transcode_to_16(
             tag_t<format::utf32>,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out)
         {
@@ -332,7 +332,7 @@ namespace boost::parser::detail { namespace text {
         transcode_result<Iter, OutIter> transcode_to_32(
             tag_t<format::utf32>,
             Iter first,
-            Sentinel last,
+            Sentinel const & last,
             std::ptrdiff_t n,
             OutIter out)
         {

From 284a42843d8bdca2db1f7b87f67edcbbcb659df1 Mon Sep 17 00:00:00 2001
From: Andreas Buhr <andreas@andreasbuhr.de>
Date: Wed, 10 Dec 2025 17:51:04 +0100
Subject: [PATCH 7/8] pass end iterator by const-ref

---
 include/boost/parser/parser.hpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/boost/parser/parser.hpp b/include/boost/parser/parser.hpp
index 3e8e55c3..a3c1f7cf 100644
--- a/include/boost/parser/parser.hpp
+++ b/include/boost/parser/parser.hpp
@@ -455,7 +455,7 @@ namespace boost { namespace parser {
             static constexpr bool do_trace = DoTrace;
             static constexpr bool use_callbacks = UseCallbacks;
 
-            I first_;
+            I const & first_;
             S const & last_;
             bool * pass_ = nullptr;
             int * trace_indent_ = nullptr;
@@ -524,7 +524,7 @@ namespace boost { namespace parser {
             parse_context(
                 std::bool_constant<DoTrace>,
                 std::bool_constant<UseCallbacks>,
-                I & first,
+                I const & first,
                 S const & last,
                 bool & success,
                 int & indent,
@@ -547,7 +547,7 @@ namespace boost { namespace parser {
             parse_context(
                 std::bool_constant<DoTrace>,
                 std::bool_constant<UseCallbacks>,
-                I & first,
+                I const & first,
                 S const & last,
                 bool & success,
                 int & indent,
@@ -565,7 +565,7 @@ namespace boost { namespace parser {
             parse_context(
                 std::bool_constant<DoTrace>,
                 std::bool_constant<UseCallbacks>,
-                I & first,
+                I const & first,
                 S const & last,
                 bool & success,
                 int & indent,

From 870b07eca1334d924030a3417dcd73c2fb3803cc Mon Sep 17 00:00:00 2001
From: Andreas Buhr <andreas@andreasbuhr.de>
Date: Wed, 10 Dec 2025 18:22:27 +0100
Subject: [PATCH 8/8] pass end iterator by const-ref

---
 include/boost/parser/detail/text/algorithm.hpp | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/boost/parser/detail/text/algorithm.hpp b/include/boost/parser/detail/text/algorithm.hpp
index 09660a52..058aa584 100644
--- a/include/boost/parser/detail/text/algorithm.hpp
+++ b/include/boost/parser/detail/text/algorithm.hpp
@@ -21,7 +21,7 @@ namespace boost::parser::detail { namespace text {
 
     namespace detail {
         template<typename Iter>
-        std::ptrdiff_t distance(Iter first, Iter const & last, non_sentinel_tag)
+        std::ptrdiff_t distance(Iter const & first, Iter const & last, non_sentinel_tag)
         {
             return std::distance(first, last);
         }
@@ -41,7 +41,7 @@ namespace boost::parser::detail { namespace text {
     /** Range-friendly version of `std::distance()`, taking an iterator and a
         sentinel. */
     template<typename Iter, typename Sentinel>
-    std::ptrdiff_t distance(Iter first, Sentinel const & last)
+    std::ptrdiff_t distance(Iter const & first, Sentinel const & last)
     {
         return detail::distance(
             first,
@@ -107,7 +107,7 @@ namespace boost::parser::detail { namespace text {
     /** Analogue of `std::find()` that finds the last value in `[first, last)`
         equal to `x`. */
     template<typename BidiIter, typename T>
-    BidiIter find_backward(BidiIter first, BidiIter last, T const & x)
+    BidiIter find_backward(BidiIter const & first, BidiIter const & last, T const & x)
     {
         auto it = last;
         while (it != first) {
@@ -120,7 +120,7 @@ namespace boost::parser::detail { namespace text {
     /** Analogue of `std::find()` that finds the last value in `[first, last)`
         not equal to `x`. */
     template<typename BidiIter, typename T>
-    BidiIter find_not_backward(BidiIter first, BidiIter last, T const & x)
+    BidiIter find_not_backward(BidiIter const & first, BidiIter const & last, T const & x)
     {
         auto it = last;
         while (it != first) {
@@ -133,7 +133,7 @@ namespace boost::parser::detail { namespace text {
     /** Analogue of `std::find()` that finds the last value `v` in `[first,
         last)` for which `p(v)` is true. */
     template<typename BidiIter, typename Pred>
-    BidiIter find_if_backward(BidiIter first, BidiIter last, Pred p)
+    BidiIter find_if_backward(BidiIter const & first, BidiIter const & last, Pred p)
     {
         auto it = last;
         while (it != first) {
@@ -146,7 +146,7 @@ namespace boost::parser::detail { namespace text {
     /** Analogue of `std::find()` that finds the last value `v` in `[first,
         last)` for which `p(v)` is false. */
     template<typename BidiIter, typename Pred>
-    BidiIter find_if_not_backward(BidiIter first, BidiIter last, Pred p)
+    BidiIter find_if_not_backward(BidiIter const & first, BidiIter const & last, Pred p)
     {
         auto it = last;
         while (it != first) {
@@ -290,9 +290,9 @@ namespace boost::parser::detail { namespace text {
         typename Iter2,
         typename Sentinel2>
     int lexicographical_compare_three_way(
-        Iter1 first1,
+        Iter1 const & first1,
         Sentinel1 const & last1,
-        Iter2 first2,
+        Iter2 const & first2,
         Sentinel2 const & last2)
     {
         auto const iters = boost::parser::detail::text::mismatch(first1, last1, first2, last2);