Re: openDir is confusing

readDir returns what is in the directory, while you might prefer an  
absolute
path, others might want something different.  There are two easy  
solutions to
your problem.  One is that you can change the working directory as  
you walk the
tree, or you could implement your own version of directory streams:

   structure MyDirstream =
     struct
       datatype dirstream = DS of {path : string, ds :  
OS.FileSys.dirstream}
       fun openDir s = DS{path = s, ds = OS.FileSys.openDir s}
       fun readDir (DS{path, ds}) = (case OS.FileSys.readDir ds
	     of SOME f => SOME(OS.Path.concat(path, f))
	      | NONE => NONE
	    (* end case *))
       fun closeDir (DS{ds, ...}) = OS.FileSys.closeDir ds
       fun rewindDir (DS{ds, ...}) = OS.FileSys.rewindDir ds
     end

On Nov 16, 2006, at 1:12 AM, brian wrote:

> I'm tyring to write a file tree "visitor" function and I find the
> operation of openDir/readDir to be somewhat hard to work with.
>
> An example is always good to start with:
>
>
> d = openDir("somelongpathname")
> readDir(d) => "foo" -- a file
> readDir(d) => "bar" -- a directory
>
> d2 = opendir("bar")
>
> error - no such file or directory
>
> Of course, this is correct, because I did not pass in the full
> pathname.  Therein lies the problem, I think.  It seems as I'm
> traversing the directory, I would have to maintain the path which
> readDir is operating from.  So why doesn't readDir simply return the
> FULL path in the first place instead of just the pathname ?
>
> Am I missing something, or should I be using some different
> functionality ?
>
> Thanks
>
> Brian
>
>
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