Re: defvaralias

[Nick Roberts <nickrob@snap.net.nz>]

Luc Teirlinck writes:
 > Nick Roberts wrote:
 >     
 >     > (defvar var1 "DOC1")
 >     > (defvar var2 "DOC2")
 >     > (defvaralias 'var1 'var2)
 > 
 >    I think if an alias is made only then only one of the variables needs to be
 >    declared.
 > 
 > So the idea of the present behavior would be to do a
 > (defvaralias 'var1 'var2) with a defvar for var1 instead of for var2?
 > I do not believe that would be appropriate.

I mean:

(defvar var2 "DOC2")
(defvaralias 'var1 'var2)

is doesn't give compiler warnings. Presumably defvaralias is a declaration
for var1.

 >    As Stefan has pointed out defvaralias has a symmetry in its
 >    arguments (unlike define-obsolete-variable-alias neither)
 > 
 > I do not understand.  The variable alias structure is a directed
 > graph, not an undirected graph.  The arguments to defvaralias are
 > asymmetric in their meaning.  The first argument is the alias, the
 > second the base variable.
 > 
 > (defvaralias 'var1 'var2)
 > 
 > is different (in non-trivial ways) from 
 > 
 > (defvaralias 'var2 'var1)
 > 

Yes, you're right and I'm misquoting Stefan. There must be some symmetry,
however as:

(defvar var2 "DOC2")
(defvaralias 'var1 'var2)
(defvar var1a "DOC1")
(defvaralias 'var1a 'var2a)

doesn't give compiler warnings either.


Nick


 > in as far as `indirect-variable', cyclic variable indirection errors
 > and such are concerned.
 > 
 > Sincerely,
 > 
 > Luc.