Beman Dawes wrote: > At 06:03 AM 8/14/2003, Walter Landry wrote: > It would be trivial to add an additional path constructor that takes a > checking function or function object. > > But that would kill ease-of-use. It is one thing to require an > additional constructor argument in the fairly limited use "native" > case, but the portability checking is applied to each and every path > object constructed, including the many path temporaries created by > the automatic conversions > from char * and string.
You could have the checking functor as a pointer to a boost::function which is a default argument initialized to 0. That wouldn't kill ease of use or change anything for the users who are very happy with the current posix default. > > (That "kill ease-of-use" point might be hard to understand if you > haven't actually written code using the library. The automatic > conversions really > do allow "script-like" programming ease, and are reasonably safe > given the conversion result is class path.) > > Also, the portability checking policy often needs to propagate to > called functions such as third party liberties. Adding overloads of > functions to take an additional argument is also too messy, and > doesn't provide for automatic pass-through to lower level functions. I think this is an excuse for a certain amount of additional rewriting of the library. How you propagate the functor pointer is your own business but we all have been faced with problems like this when adding a new feature to an implementation. Internally, do what you need to do but for the end-user I think you need to consider what is best and most flexible for him. > In most (but not all) programs it really would be convenient if > portability checking policy was a global. But of course we all know > that "global variables are consider harmful". There are also several > valid use cases where a program needs to switch back and forth > between portability policies. Yes, not all portability policies need to theoretically be the same. There are cases when an OS accepts a file name in one instance, such as iteratoring through wildcard names, whereas another instance it does not accept the same notation, such as determining whether or not a specific file exists. So I think you need to allow portability policies on an instance by instance basis. _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
