Re: [boost] Filesystem I18n comments

From: Beman Dawes (bdawes_at_[hidden])
Date: 2005-12-29 13:41:25

"Martin" <adrianm_at_[hidden]> wrote in message 
news:loom.20051228T091806-138_at_post.gmane.org...

> 1. Why "directory_iterator->exists()" instead of 
> "exists(directory_iterator)"

If an "exists(directory_iterator)" overload was supplied, it would be really 
easy to write "exists(itr)" when you meant "exists(itr->path())". Functions 
with different semantics should have different syntax. At least that was the 
theory.

> 2. Any chance of having a non-throwing version of directory_iterator 
> (similar
> to status). Since such a common error like not having access to a 
> directory
> throws an exception, every directory_iterator construction needs a 
> try/catch.
> The recursive_directory_iterator is kind of useless since it will stop as 
> soon
> as you get an "access denied".
> (Maybe a portable can_be_iterated function can be added)

Hum.  Worth considering.

Aside: I'm fascinated with the idea of non-ignorable error codes. With a 
constructor, the code would have to be by argument rather than return.

> 3. The documentation doesn't say how other_flag is supposed to work. If an
> implementation adds more flags, will other_flag be set for these?

I don't know. Haven't given it any thought yet.

> 4. A suggestion is to overload exists, is_directory etc for status flags 
> and
> let the error condition be statusflags == 0. (or make status_flags a class
> with a bool conversion)
>
> In the code you could then write like
>
> if (status_flags s = status(path)) {
>  if (!exists(s) || !is_directory(s))
>    cout << "bad directory";
> }
> else
>  cout << "error";
>
> In the current implementation you need to remember if you should use == or 
> &
> when checking the status flags.
>
> status_flags s = status(path);
> if (s == error_flag) // must test with == here
>  cout << "error";
> else if ((s & directory_flag) == 0) // must test with & here
>  cout << "bad directory";

Interesting idea. POSIX does something similar with macros. I'll give it 
some thought.

Thanks for the comments,

--Beman