Re: enough-namestring doesn't work?

On 5/29/23 08:56, Camm Maguire wrote:
> Greetings, and thanks for your feedback!
>
> (enough-namestring #P"/a/b/c/d.txt" #P"/a/b/c/") -> "d.txt"

This is right, but I think getting the directory components is important 
too.  For the example I gave, the answer from gcl is not the shortest 
reasonable string that satisfies the criterion.  The shortest is "c/d.txt".

For the particular case I was looking at (from maxima), I don't have to 
use enough-namestring because the pathnames I have are from directory so 
it's easy to strip of the leading parts (assuming directory didn't 
follow symlinks to get a totally different directory).  But 
enough-namestring seems to be the natural way to strip off the leading 
parts of the path.

>
> gcl's version does not unpack the directory component into segments but
> just compares the pathanme components with the default as whole units:
>
> (DEFUN ENOUGH-NAMESTRING
>         (X &OPTIONAL (DEF *DEFAULT-PATHNAME-DEFAULTS*) &AUX
>            (PX (PATHNAME X)) (PDEF (PATHNAME DEF)))
>    (DECLARE (OPTIMIZE (SAFETY 1)))
>    (CHECK-TYPE X PATHNAME-DESIGNATOR)
>    (CHECK-TYPE DEF PATHNAME-DESIGNATOR)
>    (NAMESTRING
>        (MAKE-PATHNAME :HOST
>            (LET ((K (PATHNAME-HOST PX)))
>              (UNLESS (EQUAL K (PATHNAME-HOST PDEF)) K))
>            :DEVICE
>            (LET ((K (PATHNAME-DEVICE PX)))
>              (UNLESS (EQUAL K (PATHNAME-DEVICE PDEF)) K))
>            :DIRECTORY
>            (LET ((K (PATHNAME-DIRECTORY PX)))
>              (UNLESS (EQUAL K (PATHNAME-DIRECTORY PDEF)) K))
>            :NAME
>            (LET ((K (PATHNAME-NAME PX)))
>              (UNLESS (EQUAL K (PATHNAME-NAME PDEF)) K))
>            :TYPE
>            (LET ((K (PATHNAME-TYPE PX)))
>              (UNLESS (EQUAL K (PATHNAME-TYPE PDEF)) K))
>            :VERSION
>            (LET ((K (PATHNAME-VERSION PX)))
>              (UNLESS (EQUAL K (PATHNAME-VERSION PDEF)) K)))))
>
> It seems this is compliant given the spec:
>
> =============================================================================
> enough-namestring returns an abbreviated namestring that is just sufficient to identify the file named by pathname when considered relative to the defaults. It is required that
>
>   (merge-pathnames (enough-namestring pathname defaults) defaults)
> ==  (merge-pathnames (parse-namestring pathname nil defaults) defaults)
>
> in all cases, and the result of enough-namestring is the shortest reasonable string that will satisfy this criterion.
>
> It is not necessarily possible to construct a valid namestring by concatenating some of the three shorter namestrings in some order.
> =============================================================================
>
> Perhaps this could be improved.
>
> Take care,
>
> Raymond Toy <[email protected]> writes:
>
>> I tried the followin: (enough-namestring #P"/a/b/c/d.txt" #P"/a/b/"). I was expecting "c/d.txt". But gcl 2.6.13 release returns “/a/b/c/d.txt”. I actually can’t find any example where enough-namestring produces anything other than the namestring for the
>> first arg.
>>
>> How do I invoke enough-namestring to produce what I want, like other lisps do?
>>
>> ​
>>