[Armedbear-devel] export doesn't work

[Pascal J. Bourguignon]

bonasso <bonasso at traclabs.com> writes:

> Whenever I try to export a symbol to cl-user from another package,
> like (export '(memory-apropos) :cl-user) while in a package called
> memory I get
>
> "The symbol memory-apropos is not accessible in package
> COMMON-LISP-USER"
>
> But if I do:
>
> (in-package :cl-user)
> (import 'memory::memory-apropos)
>
> it works.
>
> Is this a bug?

There's no bug here.


With:

    (in-package :memory)
    (export '(memory-apropos) :cl-user)

you're asking to export from the package named "CL-USER", the symbol
MEMORY::MEMORY-APROPOS that is interned into MEMORY when the lisp reader
reads the EXPORT form.  Since this symbol MEMORY::MEMORY-APROPOS is not
present in the CL-USER package, it cannot be exported from the CL-USER
package, and therefore an error is correctly signaled.

You either import memory::memory-apropos into cl-user before exporting
it:

    (in-package :memory)
    (import '(memory-apropos) :cl-user)
    (export '(memory-apropos) :cl-user)

or you could import cl-user::memory-apropos into memory before exporting
it:

    (in-package :memory)
    (unintern 'memory-apropos) ; remove the old one
    (import '(cl-user::memory-apropos) :memory)
    (export '(memory-apropos) :cl-user)

But in both cases, it's a little strange to be exporting from cl-user a
symbol, the more so when it actually comes from the memory package.

Package named <something>-USER are intended to be leaves in the package
dependency graph, so they usually don't export any symbol, and no other
package uses them.  Exporting a symbol from a package is only useful if
you want to use that package, or if you want to use a single colon
instead of the double colon to qualify those symbols.


-- 
__Pascal Bourguignon__
http://www.informatimago.com/
"Le mercure monte ?  C'est le moment d'acheter !"


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