Re: [Boost-users] boost exception tutorial

Something that confuses me a little in the exception documentation is the struct tag used when typedef'ing error_info<>. It's unclear if these tags are coming from boost exception headers, std headers (like the in the case below) or if these must be explicitly defined by the user, or if the simple fact that of using them in the typedef is enough to declare them.

typedef boost::error_info std_range_min;

So the above is equivalent to the below?

struct tag_std_range_min; typedef boost::error_info std_range_min;

It may not be obvious to everyone ;-)  Wasn't to me at first.  Thanks, --DD

I'm certainly not an expert on boost::exception (just started integrating it into my project a few days ago), but it appears to me that the purpose is twofold: -You can easily have multiple error_info objects which hold the same type of data, but for different purposes. Say for example a file loading error, where you want to report the filename and a description of the error in two seperate error_info's; using the struct type as a template parameter gives you a way to easily distinguish between them. -It allows you to describe the information the error_info contains once, when you declare the struct in the typedef. Saves you from having to type in the info every time you use a particular error_info Hope that helps, MC