From 5e816dfdd7f73b1bf58533c4f5aa3f78d8de2a58 Mon Sep 17 00:00:00 2001
From: Rainer Kuemmerle <rainer.kuemmerle@gmail.com>
Date: Tue, 13 Aug 2024 12:53:39 +0200
Subject: [PATCH 1/2] Implement joining iterator ranges into a string

---
 g2o/stuff/string_tools.h               | 26 ++++++++++++++++++++++++++
 unit_test/stuff/string_tools_tests.cpp |  8 ++++++++
 2 files changed, 34 insertions(+)

diff --git a/g2o/stuff/string_tools.h b/g2o/stuff/string_tools.h
index 08cecaf12..d97011469 100644
--- a/g2o/stuff/string_tools.h
+++ b/g2o/stuff/string_tools.h
@@ -27,6 +27,8 @@
 #ifndef G2O_STRING_TOOLS_H
 #define G2O_STRING_TOOLS_H
 
+#include <algorithm>
+#include <iterator>
 #include <sstream>
 #include <string>
 #include <vector>
@@ -115,6 +117,30 @@ G2O_STUFF_API std::string strExpandFilename(const std::string& filename);
 G2O_STUFF_API std::vector<std::string> strSplit(const std::string& s,
                                                 const std::string& delim);
 
+/**
+ * @brief Join into a string using a delimeter
+ *
+ * @tparam Iterator
+ * @tparam std::iterator_traits<Iterator>::value_type
+ * @param b begin of the range for output
+ * @param e end of the range for output
+ * @param delimiter will be inserted in between elements
+ * @return std::string joined string
+ */
+template <typename Iterator,
+          typename Value = typename std::iterator_traits<Iterator>::value_type>
+std::string strJoin(Iterator b, Iterator e, const std::string& delimiter = "") {
+  if (b == e) return "";
+  std::ostringstream os;
+  std::copy(b, std::prev(e),
+            std::ostream_iterator<Value>(os, delimiter.c_str()));
+  b = std::prev(e);
+  if (b != e) {
+    os << *b;
+  }
+  return os.str();
+}
+
 /**
  * read a line from is into currentLine.
  * @return the number of characters read into currentLine (excluding newline),
diff --git a/unit_test/stuff/string_tools_tests.cpp b/unit_test/stuff/string_tools_tests.cpp
index b5dbc5f42..9d2251d44 100644
--- a/unit_test/stuff/string_tools_tests.cpp
+++ b/unit_test/stuff/string_tools_tests.cpp
@@ -79,6 +79,14 @@ TEST(Stuff, StrSplit) {
     ASSERT_EQ(std::to_string(i + 1), tokens[i]);
 }
 
+TEST(Stuff, StrJoin) {
+  std::vector<int> int_data = {1, 2, 3};
+  EXPECT_EQ("123", g2o::strJoin(int_data.begin(), int_data.end()));
+  EXPECT_EQ("1", g2o::strJoin(int_data.begin(), std::next(int_data.begin())));
+  EXPECT_EQ("", g2o::strJoin(int_data.begin(), int_data.begin()));
+  EXPECT_EQ("1, 2, 3", g2o::strJoin(int_data.begin(), int_data.end(), ", "));
+}
+
 TEST(Stuff, StrStartsWith) {
   ASSERT_FALSE(g2o::strStartsWith("Hello World!", "World!"));
   ASSERT_TRUE(g2o::strStartsWith("Hello World!", "Hello"));

From b6ebf6f68754b6a91deb16a24b2a557658967dbc Mon Sep 17 00:00:00 2001
From: Rainer Kuemmerle <rainer.kuemmerle@gmail.com>
Date: Tue, 13 Aug 2024 12:54:27 +0200
Subject: [PATCH 2/2] Use strJoin instead of fmt::join

Fix #825
---
 g2o/core/optimizable_graph.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/g2o/core/optimizable_graph.cpp b/g2o/core/optimizable_graph.cpp
index 7fbbe30d1..7fc350281 100644
--- a/g2o/core/optimizable_graph.cpp
+++ b/g2o/core/optimizable_graph.cpp
@@ -473,14 +473,14 @@ bool OptimizableGraph::load(istream& is) {
       }
       if (!vertsOkay) {
         G2O_ERROR("Unable to find vertices for edge {} at line {} IDs: {}",
-                  token, lineNumber, fmt::join(ids, " "));
+                  token, lineNumber, strJoin(ids.begin(), ids.end(), " "));
         delete e;
         e = nullptr;
       } else {
         bool r = e->read(currentLine);
         if (!r || !addEdge(e)) {
           G2O_ERROR("Unable to add edge {} at line {} IDs: {}", token,
-                    lineNumber, fmt::join(ids, " "));
+                    lineNumber, strJoin(ids.begin(), ids.end(), " "));
           delete e;
           e = nullptr;
         }