Re: bug in function {metavariable}:name

[prunet@oaxaca.inria.fr (Vincent Prunet)]

In article <34574@sophia.inria.fr>, Guido.Bosch@loria.fr (Guido Bosch) writes:
|> In Centaur 1.2, the function {metavariable}:name returns/modifies  not
|> the name of a metavariable, but it's operator. This is not only
|> anoying, but also dangerous. 
|> 
|> Here is a script that shows you what I mean (I also verified with a
|> plain Centaur without VTP++ and object browser - it's the same behavior)
|>  
|> 
|> ? meta
|> = #<Glider metavariable MODULE_NAME1>
|> ? ;;; Describe object
|> #<Glider metavariable MODULE_NAME1> is a #:tree:Glider:meta
|>   name: fragment-Glider-meta
|>   operator: #<operator meta>
|>   sons: ((MODULE_NAME1 . 0) tree)
|>   father: #<Glider module_header>
|> = ()
|> ? ({metavariable}:name meta)
|> = #<operator meta>
|> ? (eq ({metavariable}:name meta) ({tree}:operator meta))
|> = t
|> 
|> ;; this is was I really wanted to get or modify 
|> ? (caar ({tree}:sons meta))
|> = MODULE_NAME1
|> ? 

I already posted some explanations about the structure of metavariables. I
repost the same message (20 august 1992, in answer to a question raised by
Guido Bosch):

------
A metavariable tree is not a metavariable.
A metavariable is not a tree.


A metavariable tree is an atomic tree, its atom_class is metavariable, its
atom value is a metavariable.


The metavariable operator of a given formalism may be obtained by the call :

({formalism}:metavarop <formalism>).


I noticed an error in the documentation of the Virtual Tree Processor, page
24.

Here is the correct definition of the {formalism}:tree function:

(de {formalism}:tree (formalism name class . tagval)
    ({tree}:make ({formalism}:metavarop formalism)
     (apply '{name}:metavariable name class tagval)))


Vincent

-------



Example of correct use:


? (setq form ({name}:formalism 'error))
= #[error 0 ((((comment_s * ((COMMENT ((meta 0 metavariable) (#[error 0 ((((
comment_s * ((COMMENT ((meta 0 metavariable) (#[error 0 ((((comment_s *...

? (setq metavarop ({formalism}:metavarop form))
= ((meta 0 metavariable) (#[error 0 ((((comment_s * ((COMMENT ((meta 0 
metavariable) (#[error 0 ((((comment_s * ((COMMENT ((meta 0 metavariable) ...

;; the meta operator is atomic.
? ({operator}:atomic metavarop)
= t

;; the class of atom values is metavariable.
? ({operator}:class metavarop)
= metavariable

;; make a metavariable tree.
? (setq tree ({formalism}:tree form "foo" {tree}))
= ((((meta 0 metavariable) (#[error 0 ((((comment_s * ((COMMENT ((meta 0 
metavariable) (#[error 0 ((((comment_s * ((COMMENT ((meta 0 metavariable) ...

;; check the operator.
? (eq ({tree}:operator tree) metavarop)
= t

;; get the value, a metavariable.
? (setq metavar ({tree}:atom_value tree))
= ((foo . 0) tree)

;; check the metavariable name and class.
? ({metavariable}:name metavar)
= foo
? ({metavariable}:class metavar)
= tree

-- 
Vincent Prunet, Sema Group Sophia Antipolis
INRIA       BP 93    06902 SOPHIA ANTIPOLIS Cedex  FRANCE
prunet@sophia.inria.fr, (33) 93 65 78 42, Fax:(33) 93 65 77 66