From 1f0969f86e9d4debeb2f73a7f4d82eb6c190f0df Mon Sep 17 00:00:00 2001
From: Andreas Buhr <andreas@andreasbuhr.de>
Date: Tue, 31 Mar 2026 10:07:35 +0200
Subject: [PATCH] Performance optimization for or_parser

Only apply skip once, not for every option
---
 include/boost/parser/parser.hpp | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/boost/parser/parser.hpp b/include/boost/parser/parser.hpp
index 1c5585f3..fd45462c 100644
--- a/include/boost/parser/parser.hpp
+++ b/include/boost/parser/parser.hpp
@@ -3396,7 +3396,6 @@ namespace boost { namespace parser {
             template<typename Parser>
             auto operator()(Parser const & parser) const
             {
-                detail::skip(first_, last_, skip_, flags_);
                 success_ = true; // In case someone earlier already failed...
                 return parser.call(
                     first_,
@@ -3410,7 +3409,6 @@ namespace boost { namespace parser {
             template<typename Parser, typename Attribute>
             void operator()(Parser const & parser, Attribute & retval) const
             {
-                detail::skip(first_, last_, skip_, flags_);
                 success_ = true; // In case someone earlier already failed...
 
                 detail::apply_parser(
@@ -3518,6 +3516,7 @@ namespace boost { namespace parser {
                 *this, first, last, context, flags, retval);
 #endif
 
+            auto unmodified_first = first;
             use_parser_t<Iter, Sentinel, Context, SkipParser> const use_parser{
                 first, last, context, skip, flags, success};
 
@@ -3539,12 +3538,16 @@ namespace boost { namespace parser {
                 else
                     use_parser.first_ = prev_first;
             };
+            detail::skip(first, last, skip, flags);
+
             std::apply([&try_parser](auto&&... args) {
                 ((try_parser(args)), ...);
             }, parsers_);
 
-            if (!done)
+            if (!done) {
                 success = false;
+                first = unmodified_first;
+            }
         }
 
 #ifndef BOOST_PARSER_DOXYGEN