Positional arguments

[wavexx]

It would be nice to improve a bit the handling of positional arguments to be
more unix-y. A practical example of what I'd have in mind:

cxxopts::Options options(argv[0], " - example command line options");
options.add_options()
  ("f,flag", "desc")
  ("input", "", cxxopts::value<string>(input), "INPUT")
  ("output", "", cxxopts::value<string>(output), "OUTPUT");
opts.parse(argc, argv, {"input", "output"});

Where:

• the empty description suppresses the help for that option
• the third argument to Options::parse is a list of positional arguments.
  Just a vector<string>, which is moved to m_positional (now a vector<string>
  as well).
• short usage also iterates though m_positional to find argument names for
  consistent short help.
• parse() finally consumes positional arguments in a simple loop.
  If a vector<> is encountered, it just eats all the remaining arguments.
• parse_positional() is now just a compatibility stub that adds an element
  to m_positional, although I find it less clear than the above behavior.

This should result in the following help:

Usage:
  ./example [OPTION...] INPUT OUTPUT - example command line options

  -f, --flag desc

With no changes to the public interface (and minimal source changes as well).

[jarro2783]

This sounds pretty reasonable. Are you suggesting that you would be able to make the changes?

Just so I understand, you want to link positional arguments to different named arguments? At the moment I think it just puts everything into one positional argument. So in the above example, parsing the first positional argument lets me get it as options.get['input'] and the second as options.get['output'].

I'm not sure what you mean by eating the remaining arguments. Do you mean that if one of the positional arguments takes a vector then it just gets all the rest of the positional arguments?

[wavexx]

On 10/09/15 06:38, jarro2783 wrote:

This sounds pretty reasonable. Are you suggesting that you would be able
to make the changes?

I would be, though not now. I was looking at the code too see if this
would be possible, and it looks like.

Just so I understand, you want to link positional arguments to different
named arguments? At the moment I think it just puts everything into one
positional argument. So in the above example, parsing the first
positional argument lets me get it as |options.get['input']| and the
second as |options.get['output']|.

Yes.

I'm not sure what you mean by eating the remaining arguments. Do you
mean that if one of the positional arguments takes a vector then it just
gets all the rest of the positional arguments?

Right. It's pretty common for me to have:

$ cmd [flags] cmd file [file ...]

With the above, if you link "file" to vector, you effectively
get all the final positional arguments.

Granted, you can do the same without, but I think it would be a nice touch.

[jarro2783]

I don't think it's hard. I'm not really in a position to do it right now either. We can leave this issue open and someone can do it eventually. Let us know if you feel like doing it before I do.

[jarro2783]

I'm working on this now.

[jarro2783]

This is done now.