From d762f869f2bc72a3d67e9daca49e7e807d773651 Mon Sep 17 00:00:00 2001
From: Rosen Penev <rosenp@gmail.com>
Date: Sun, 1 Nov 2020 20:41:25 -0800
Subject: [PATCH] replace for loop with std::transform

Seems to be a small performance boost with make test.

Total Test time (real) =   5.17 sec

vs

Total Test time (real) =   5.11 sec

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 include/cxxopts.hpp | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/cxxopts.hpp b/include/cxxopts.hpp
index dd4f31e..929d822 100644
--- a/include/cxxopts.hpp
+++ b/include/cxxopts.hpp
@@ -2225,12 +2225,16 @@ void
 Options::generate_all_groups_help(String& result) const
 {
   std::vector<std::string> all_groups;
-  all_groups.reserve(m_help.size());
 
-  for (const auto& group : m_help)
-  {
-    all_groups.push_back(group.first);
-  }
+  std::transform(
+    m_help.begin(),
+    m_help.end(),
+    std::back_inserter(all_groups),
+    [] (const std::map<std::string, HelpGroupDetails>::value_type& group)
+    {
+      return group.first;
+    }
+  );
 
   generate_group_help(result, all_groups);
 }