parse groups

src/cxxopts.cpp

@@ -363,7 +363,7 @@ Options::add_option
 
   //add the help details
   auto& options = m_help[group];
-  options.push_back(HelpDetails{s, l, desc, value->has_arg()});
+  options.options.push_back(HelpOptionDetails{s, l, desc, value->has_arg()});
 }
 
 void
@@ -382,11 +382,11 @@ Options::add_one_option
 }
 
 std::string
-Options::help() const
+Options::help_one_group(const std::string& g) const
 {
   typedef std::vector<std::pair<std::string, std::string>> OptionHelp;
 
-  auto group = m_help.find("");
+  auto group = m_help.find(g);
   if (group == m_help.end())
   {
     return "";
@@ -396,10 +396,14 @@ Options::help() const
 
   size_t longest = 0;
 
-  std::string result = "Usage:\n  " + m_program + " [OPTION...] " 
-    + m_help_string + "\n\n";
+  std::string result;
+  
+  if (!g.empty())
+  {
+    result += " " + g + " options:\n\n";
+  }
 
-  for (const auto& o : group->second)
+  for (const auto& o : group->second.options)
   {
     auto s = format_option(o.s, o.l, o.has_arg);
     longest = std::max(longest, s.size());
@@ -412,7 +416,7 @@ Options::help() const
   int allowed = 76 - longest - OPTION_DESC_GAP;
 
   auto fiter = format.begin();
-  for (const auto& o : group->second)
+  for (const auto& o : group->second.options)
   {
     auto d = format_description(o.desc, longest + OPTION_DESC_GAP, allowed);
 
@@ -436,4 +440,18 @@ Options::help() const
   return result;
 }
 
+std::string
+Options::help(const std::vector<std::string>& groups) const
+{
+  std::string result = "Usage:\n  " + m_program + " [OPTION...] " 
+    + m_help_string + "\n\n";
+
+  for (const auto& g : groups)
+  {
+    result += help_one_group(g);
+  }
+
+  return result;
+}
+
 }

src/cxxopts.hpp

@@ -326,7 +326,7 @@ namespace cxxopts
     int m_count;
   };
 
-  struct HelpDetails
+  struct HelpOptionDetails
   {
     std::string s;
     std::string l;
@@ -334,6 +334,13 @@ namespace cxxopts
     bool has_arg;
   };
 
+  struct HelpGroupDetails
+  {
+    std::string name;
+    std::string description;
+    std::vector<HelpOptionDetails> options;
+  };
+
   class Options
   {
     public:
@@ -390,7 +397,7 @@ namespace cxxopts
     parse_positional(std::string option);
 
     std::string
-    help() const;
+    help(const std::vector<std::string>& groups = {""}) const;
 
     private:
     
@@ -425,6 +432,9 @@ namespace cxxopts
       const std::string& name
     );
 
+    std::string
+    help_one_group(const std::string& group) const;
+
     std::string m_program;
     std::string m_help_string;
 
@@ -432,7 +442,7 @@ namespace cxxopts
     std::string m_positional;
 
     //mapping from groups to help options
-    std::map<std::string, std::vector<HelpDetails>> m_help;
+    std::map<std::string, HelpGroupDetails> m_help;
   };
 
   class OptionAdder

src/example.cpp

@@ -48,10 +48,20 @@ int main(int argc, char* argv[])
       ("option_that_is_too_long_for_the_help", "A very long option")
     ;
 
+    options.add_options("Group")
+      ("c,compile", "compile")
+      ("d,drop", "drop", cxxopts::value<std::vector<std::string>>());
+
     options.parse_positional("positional");
 
     options.parse(argc, argv);
 
+    if (options.count("help"))
+    {
+      std::cout << options.help({"", "Group"}) << std::endl;
+      exit(0);
+    }
+
     if (apple)
     {
       std::cout << "Saw option ‘a’" << std::endl;
@@ -72,11 +82,6 @@ int main(int argc, char* argv[])
       }
     }
 
-    if (options.count("help"))
-    {
-      std::cout << options.help() << std::endl;
-    }
-
     if (options.count("positional"))
     {
       std::cout << "Positional = " << options["positional"].as<std::string>()