Relative vs. Absolute paths (was Re: [Axiom-developer] HyperDoc)

[C Y]

--- Waldek Hebisch <address@hidden> wrote:

> Relative $AXIOM have to change when you change directory.

Um.  I'm not quite following you here Waldek - isn't that the whole
point of relative linking?  We set $AXIOM once to define where the
toplevel Axiom directory is located, and then everything else changes
automatically?

> This means that some variable settings have to be repeated.  Passing
> of filenames to programs working in different directory become
> harder.

Can you give an example?  I'm missing something, I think - what is the
difference between having $AXIOM/lib/lib1.spad vs.
/usr/local/axiom/mnt/linux/lib/lib1.spad?  If I am in $AXIOM/lib and I
tell the program to output to $AXIOM/bin, or I want a file in ../input/
or $AXIOM/input, (or for that matter $AXIOM/$INPUT if you want to
generalize) those should Just Work.  Perhaps lisp has some limitations
here?

> Also relative paths are likely to hardwire relative
> positions of directories, making change harder.

Now I'm really confused.  How do absolute pathnames not hardwire things
as much as relative pathnames?

> Recently I noticed that in Lisp relative paths behave in funny way
> (it looks that Axiom is frequently calling truename to make
> paths absolute and avoid problem).

I confess I have not fully understood Lisp's handling of paths as yet,
so perhaps there are some issues I am not aware of.

> So there are costs (IMHO substantial) to relative paths.
> 
> Later:
> > Oh, yeah, one more thing: mingw uses windows native tools, in
> > particular options  start with forward slash.  I don't remember the
> > exact details, but at some point some of the absolute paths (using
> > Unix-style notation) started being interpreted as options; it isn't
> funny.
> 
> Explicit drive letter should cure this problem.

Shouldn't Axiom not care at all what drive or directory it is in?  I
would think the only thing most of the system should need to know is
where other parts of the system are relative to the toplevel Axiom
directory - where that toplevel directory is located shouldn't make
much difference.  

I am sure I'm missing something important - is there an example where
the relative merits of the two approaches can be clearly seen?

Cheers,
CY


 
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