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Re: NSUser.m: NSTemporaryDirectory()

From: Pascal J. Bourguignon
Subject: Re: NSUser.m: NSTemporaryDirectory()
Date: Wed, 4 Apr 2001 19:58:04 +0200 (CEST)

> GNUstep's NSTemporaryDirectory() returns the temporary directory plus
> the user's name appended to it. In Apple's Foundation reference its
> behaviour is defined as follows:
> -----------
> NSTemporaryDirectory
> This function returns the temporary directory on the user's system. 
> NSString *NSTemporaryDirectory(void)
> Returns a string containing the path of the current temporary directory.
> If no such directory is currently available, this function returns nil.
> See also NSStandardApplicationPaths, NSStandardLibraryPaths,
> NSHomeDirectory
> ----------
> GNUstep's NSTemporaryDirectory() never returns nil.
> Are we trying to implement NeXT's behaviour or should we change
> (improve?) these things?
> Michael

If you translate the specification of MacOSX, you'll get:

      PRE: TRUE
   /* POST: ( tmpdir!=nil and tmpdir is a path-name, 
                          and for some time after, tmpdir is 
                               the path-name of a directory)
            ) or tmpdir==nil.

Note that since at any time the temporary directory may be deleted and
then a  file created with the same  name by any other  process, to all
effects, the post-condition is:

    (tmpdir!=nil and tmpdir is a path-name) or tmpdir==nil.

That is, NSTemporaryDirectory can return nil or a path name, and if it
return a  path-name, no much can be  said of it (the  joys of parallel

Since there is no other mean to determine if "there exists a temporary
directory on the user's  system", and implementation that would return
always a path-name would match the post-condition. (You can always add
false disjonctions to the post condition...).

Alternatively, an implementation that would always return nil would be
as well valid.

__Pascal_Bourguignon__              (o_ Software patents are endangering
()  ASCII ribbon against html email //\ the computer industry all around
/\  and Microsoft attachments.      V_/ the world http://lpf.ai.mit.edu/
1962:DO20I=1.100  2001:my($f)=`fortune`;  http://petition.eurolinux.org/

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