Here are the classes, structs, unions and interfaces with brief descriptions:

[detail level 12]

argagg	There are only two hard things in Computer Science: cache invalidation and naming things (Phil Karlton)
convert	The set of template instantiations that convert C-strings to other types for the option_result::as(), option_results::as(), parser_results::as(), and parser_results::all_as() methods are placed in this namespace
unexpected_argument_error	This exception is thrown when a long option is parsed and is given an argument using the "=" syntax but the option doesn't expect an argument
unexpected_option_error	This exception is thrown when an option is parsed unexpectedly such as when an argument was expected for a previous option or if an option was found that has not been defined
option_lacks_argument_error	This exception is thrown when an option requires an argument but is not provided one. This can happen if another flag was found after the option or if we simply reach the end of the command line arguments
invalid_flag	This exception is thrown when an option's flag is invalid. This can be the case if the flag is not prefixed by one or two hyphens or contains non alpha-numeric characters after the hypens. See is_valid_flag_definition() for more details
option_result	Represents a single option parse result
option_results	Represents multiple option parse results for a single option. If treated as a single parse result it defaults to the last parse result. Note that an instance of this struct is always created even if no option results are parsed for a given definition. In that case it will simply be empty
parser_results	Represents all results of the parser including options and positional arguments
definition	An option definition which essentially represents what an option is
parser_map	Contains two maps which aid in option parsing. The first map, short_map, maps from a short flag (just a character) to a pointer to the original definition that the flag represents. The second map, long_map, maps from a long flag (an std::string) to a pointer to the original definition that the flag represents
parser	A list of option definitions used to inform how to parse arguments
fmt_ostream	A convenience output stream that will accumulate what is streamed to it and then, on destruction, format the accumulated string using the fmt program (via the argagg::fmt_string() function) to the provided std::ostream
std	STL namespace