Re: The Logical Pathname (Song)

Okay, we need to infer that this is about the pathname argument. Which kind of makes sense.


a) the namestring "ASD.F" will be parsed as a logical pathname inside MERGE-PATHNAMES

CL-USER 18 > (merge-pathnames "ASD.F" "LP:FOO;QWE;")
#P"LP:ASD.F.NEWEST"



b) the namestring "ASD.F" will be parsed as a PATHNAME (unless *default-pathname-defaults* is a LOGICAL-PATHNAME).

CL-USER 19 > (merge-pathnames (parse-namestring "ASD.F") "LP:FOO;QWE;")
#P"LP:FOO;QWE;ASD.F.NEWEST"


Also: 


CL-USER 28 > (let ((*default-pathname-defaults* #p""))
               (pathname "ASD.F"))
#P"ASD.F"

CL-USER 29 > (let ((*default-pathname-defaults* "LP:FOO;QWE;"))
               (pathname "ASD.F"))
#P"LP:ASD.F"



Given that, I'd think SBCL and LispWorks have the correct result.

Regards,

Rainer


> Am 13.03.2026 um 22:15 schrieb Martin Simmons <[email protected]>:
> 
> Because the spec for merge-pathnames says it is in this case:
> 
> "merge-pathnames recognizes a logical pathname namestring when
> default-pathname is a logical pathname, or when the namestring begins with the
> name of a defined logical host followed by a colon. In the first of these two
> cases, the host portion of the logical pathname namestring and its following
> colon are optional."
> 
> -- 
> Martin Simmons
> LispWorks Ltd
> http://www.lispworks.com/
> 
> 
> 
>>>>>> On Fri, 13 Mar 2026 21:52:15 +0100, Rainer Joswig (as joswig at lisp dot de) said:
>> 
>> why would "ASD.F" be parsed as a logical pathname?
>> 
>>> Am 13.03.2026 um 21:49 schrieb Martin Simmons <[email protected]>:
>>> 
>>> Because merge-pathnames merges the directory components rather than just
>>> copying them.
>>> 
>>> The directory of "ASD.F" is (:absolute) so this overrides any directory in
>>> default-pathname.
>>> 
>>> The reason that the directory of "ASD.F" has to be (:absolute) is because that
>>> is the only way to represent a logical pathname namestring at the top level of
>>> the hierarchy.
>>> 
>>> -- 
>>> Martin Simmons
>>> LispWorks Ltd
>>> http://www.lispworks.com/
>>> 
>>> 
>>> 
>>>>>>>> On Fri, 13 Mar 2026 21:35:09 +0100, Rainer Joswig (as joswig at lisp dot de) said:
>>>> 
>>>> If it constructs a logical pathname using the host from the default-pathname, why would the directory from the default-pathname not be copied, too?
>>>> 
>>>>> Am 13.03.2026 um 19:35 schrieb Martin Simmons <[email protected]>:
>>>>> 
>>>>> It looks correct to me.  What are other CL's doing differently?
>>>>> 
>>>>> -- 
>>>>> Martin Simmons
>>>>> LispWorks Ltd
>>>>> http://www.lispworks.com/
>>>>> 
>>>>> 
>>>>> 
>>>>>>>>>> On Wed, 11 Mar 2026 19:54:07 +0100, Marco Antoniotti (as marco dot antoniotti at unimib dot it) said:
>>>>>> 
>>>>>> Hi
>>>>>> 
>>>>>> I have the following
>>>>>> 
>>>>>> CL-USER 225 >
>>>>>> (setf (logical-pathname-translations "LP")
>>>>>> '(("**;*.*.*" "~/Projects/Foo/Bar/**/")))
>>>>>> (("**;*.*.*" "~/Projects/Foo/Bar/**/"))
>>>>>> 
>>>>>> Then
>>>>>> 
>>>>>> CL-USER 256 > (merge-pathnames "ASD.F" "LP:FOO;QWE;")
>>>>>> #P"LP:ASD.F.NEWEST"
>>>>>> 
>>>>>> Which is ... different from what other CL's do.
>>>>>> 
>>>>>> Any hermeneutics about this in LW?
>>>>>> 
>>>>>> Cheers
>>>>>> MA
>>>>>> 
>>>>>> 
>>>>>> -- 
>>>>>> Marco Antoniotti, Professor, Director         tel. +39 - 02 64 48 79 01
>>>>>> DISCo, University of Milan-Bicocca U14 2043   http://dcb.disco.unimib.it
>>>>>> Viale Sarca 336
>>>>>> I-20126 Milan (MI) ITALY
>>>>>> 
>>>>>> REGAINS: https://regains.disco.unimib.it/
>>>>>> 
>>>>> 
>>>>> _______________________________________________
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>>>> 
>>>> 
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