Re: [Boost-users] [boost::program_options] optional arguments

I am at a loss of how to do that. Hopefully someone else can give you a hand. Chris On 6/12/07, Bryan Green wrote:

"Chris Weed" writes:

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On 6/12/07, Bryan Green wrote:

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Hello,

Is there a mechanism in boost::program_options for supporting optional arguments? If not, is there a suggested program_options-based alternative?

What exactly do you mean by optional arguments? Do you mean like this? http://www.boost.org/doc/html/program_options/howto.html#id1593176

Chris

The quotation in my email goes into exact detail - basically, I'm looking for functionality equivalent to GNU getopt_long, which has an "optional_argument" specifier. It is a method for optionally associating a value with a particular option. For example, if I specify a getopt_long parameter to enable listening on a socket:

{"listen",optional_argument,NULL,'l'}

Then, on the command line, '--listen' means to enable listening, using a default port number. '--listen=5000' means enable listening, using port number 5000.

The only way I see to accomplish this with program_options is to make a second option called "listen_port".

I've been playing with 'po::value()->zero_tokens()', but it does not work as I had hoped. I don't really understand how 'zero_tokens' is supposed to work, frankly. It seems to be useful when the value type is 'bool', but I don't understand its use for non-boolean types.

-Bryan

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