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.
Is this a resaonable and legal thing to do? We will need to call the map's notify() function twice, if I interpret it correctly. I suppose I could try it, but I wanted to make sure I didn't use a feature that is not part of the design, and have it disabled on me in the future.
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. 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<void, const T&> f) and reporting the *final* value twice seems weird. HTH, Volodya