Back on Wed, 25 Jun 2008 09:47:16 +0400, in gmane.comp.lib.boost.user,Vladimir Prus wrote:

Marty Fried wrote:

...

My app has a configuration file. We don't know where it will be for sure, so we are planning to make the location of the file a commandline option.

So, after reading the commandline option, we will want to parse the config file.

You don't need to call 'notify' twice -- first, parse the command line (including calling 'store' put the option into variables_map). Obtain the value of the necessary option from the variables map, and if necessary, parse the config file, again, including 'store' like:

store(parse_config_file(ifs, config_file_options), vm);

After that, call 'notify(vm)' -- once.

Thanks a lot; I didn't know the purpose of notify, and thought it might be necessary to get the data into the variables_map. This way makes sense to me, now.

I don't think that anything will break *now*, if you call notify twice, but then, the documentation say:

/** Specifies a function to be called when the final value is determined. */ typed_value* notifier(function1 f)

and reporting the *final* value twice seems weird.

That's the reason I didn't want to simply try it and assume the result is the design. Far be it for me to do something weird. :-) Thanks for your input. -- Marty Fried Senior software engineer Aldon http://www.aldon.com