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From: Beman Dawes (bdawes_at_[hidden])
Date: 2004-02-20 16:24:06

At 10:48 PM 1/25/2004, Gustavo Guerra wrote:

>Why does branch_path return path("") with simple paths like "file.ext"?
>Would'nt it make more sense to return path(".")? At least that was I was
>expecting. I had to go carefully see at documentation to discover it
>like that, because in other place in the docs its writen "A non-empty
>is specified as a precondition because an empty path is almost certainly
>This way, for example, if I have some code that gets the parent directory
>of a path and then uses that in other path operations, I'm forced to make

>special cases checking for has_branch_path, when if it returned "." it
>would work better for most cases...

In thinking more about this need, it seems to me that changing
path::branch_path() may not be the best approach. Class path member
functions work only on the lexical representation of a path, regardless of
the actual state of the external filesystem. The use cases I can think of
usually need to look at the external filesystem. Also, The decomposition
functions return elements of the path. It seems a bit surprising for a
decomposition function to return "." when it is not an element of the path.

Perhaps the use cases you are running into would be better dealt with by
new operational functions which do look at filesystem state. Two possible
functions come to mind (subject to better naming):

   path directory_path_of_file( const path & ph );

      Throws: !exists(ph) || is_directory(ph)

      Returns: branch_path(ph).empty() ? path(".") : branch_path(ph)

   path directory_path( const path & ph );

      Throws: !exists(ph)

      Returns: is_directory(ph) ? ph : directory_path_of_file(ph)



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