add join_words() utility function

doc/src/Developer_utils.rst

@@ -154,6 +154,9 @@ and parsing files or arguments.
 .. doxygenfunction:: trim_and_count_words
    :project: progguide
 
+.. doxygenfunction:: join_words
+   :project: progguide
+
 .. doxygenfunction:: split_words
    :project: progguide
 

src/utils.cpp

@@ -984,6 +984,19 @@ size_t utils::trim_and_count_words(const std::string &text, const std::string &s
   return utils::count_words(trim_comment(text), separators);
 }
 
+/* ----------------------------------------------------------------------
+   combine words in vector to single string with separator added between words
+------------------------------------------------------------------------- */
+std::string utils::join_words(const std::vector<std::string> &words, const std::string &sep)
+{
+  std::string result;
+
+  if (words.size() > 0) result = words[0];
+  for (std::size_t i = 1; i < words.size(); ++i) result += sep + words[i];
+
+  return result;
+}
+
 /* ----------------------------------------------------------------------
    Convert string into words on whitespace while handling single and
    double quotes.

src/utils.h

@@ -486,6 +486,17 @@ namespace utils {
 
   size_t trim_and_count_words(const std::string &text, const std::string &separators = " \t\r\n\f");
 
+  /*! Take list of words and join them with a given separator text.
+   *
+   * This is the inverse operation of what the split_words() function
+   * Tokenizer classes do.
+   *
+   * \param words  STL vector with strings
+   * \param sep    separator string (may be empty)
+   * \return  string with the concatenated words and separators */
+
+  std::string join_words(const std::vector<std::string> &words, const std::string &sep);
+
   /*! Take text and split into non-whitespace words.
    *
    * This can handle strings with single and double quotes, escaped quotes,