Re: Module editing; debugging with gdb

[thi <ttn@netcom.com>]

Todd Larason <jtl@molehill.org> wrote:

> On 980805, Christian Lynbech wrote:
> > Also, you may do a `(define-module (my own module))' which will make
> > that module current. If you redefine a symbol here, the new definition
> > will appear in all modules that use `(my own module)' (provided the
> > symbol was exported of course). Use `(set-current-module the-root-module)' 
> > to get back to the default module.
> 
> is that `(set-current-module the-root-module)' literal?  Or do I need to
> find the-root-module somehow?

the external representation of a module is a list.  `define-module' is
a macro so its first arg, the list describing the module, need not be
quoted.  `define-module' implicitly does a `set-current-module'.
`set-current-module' accepts a module object.  the module object
itself is a kind of record.

`the-root-module' is a module object defined by ice-9/boot-9.scm.
`(my own module)' is not a module object (it's a list of symbols).
use `resolve-module' to return an actual module object given its list
representation (quote it since `resolve-module' is not a macro).

basically, you want something like:

	(set-current-module (resolve-module '(my own module)))

here is an implementation of `@', which was discussed on this list a
while ago.  it returns an accessor procedure (a wormhole through the
module system, i like to imagine) that can resolve one symbol.

(defmacro @ args		; quality is the moment of perception
  `(lambda (sym)
     (variable-ref (module-variable (resolve-module ',args) sym))))

so, for example, you can do:

guile> (define-module (my own module))
guile> (define (negative x) (- x))		; in `(my own module)'
guile> (define-module (somewhere else))
guile> (negative 3)
     => ERROR: Unbound variable: negative
guile> (define peek-into-my-own-module (@ my own module))
guile> ((peek-into-my-own-module 'negative) 3)
     => -3

i use `@' for QA purposes, where punching holes in the paper bag is
(sort of) justifiable.  getting `@' visible to the current module is
an exercise for the reader.  (hint: what does `module-uses' tell?)

thi