[Openmcl-devel] symbols equality

[Taoufik Dachraoui]

Hi

Thank you for the reply

I cannot use T or NIL in the following case:

I have a file match.lisp as the following:

;;; file match.lisp
@::use (common-lisp)

(defun match-destruc (...)
   ....
     ((eq pat '_)  ...)
  ....)

@::public
(defmacro match (...)
   ... (match-destruc ...)
   ...)
;;; end match.lisp

Any other file using match
;; start file example.lisp
@::use (common-lisp match)
....
(defun foo (expr)
   (match expr
      ((1 _) 'ok)
      ((2 _) 'ok)
       ....))

usage:
? (mb:use 'example)
? (foo '(1 hello))

The symbol '_ matches anything

The issue is that the 'EXAMPLE::_ is not equal to 'MATCH::_

In match-destruc I can use (string= (symbol-name pat) "_") instead of (eq
pat '_)

In this case I am forced to put match-destruc in the public section (this
will export all the symbols
created by the definition of function)


Kind regards
Taoufik



On Sat, Jan 5, 2013 at 1:43 PM, Pascal J. Bourguignon <pjb at informatimago.com
> wrote:

> Taoufik Dachraoui <dachraoui.taoufik at gmail.com> writes:
>
> > Now, the issue (or annoyance) I encountered is the following:
> >
> > (make-package :test1 :use :common-lisp)
> > (make-package :test2 :use :common-lisp)
>
> This is not Common Lisp.
>
> clhs make-package:
>
>     make-package package-name &key nicknames use => package
>
>     Arguments and Values:
>
>     package-name---a string designator.
>
>     nicknames---a list of string designators. The default is the empty
> list.
>
>     use---a list of package designators. The default is
> implementation-defined.
>
> Notice the difference
> between "a list of package designators"
>     and "a designator of a list of package".
>
>
>
>
> > (in-package :test2)
> > (defun foo (e) (if (eq e 'azerty) 'ok))
> > (export 'foo)
> > (in-package :test1)
> > (use-package :test2)
> > ? (foo 'test2::azerty)
> > TEST2::OK
> > ? (foo 'azerty)
> > NIL
> > ?
> >
> > I understand that this is how it should be.
> >
> > But this poses an issue for me, because I have to use
> > (string= (symbol-name e) "AZERTY") in foo:
> >
> > (defun foo (e) (if (string= (symbol-name e) "AZERTY") 'ok))
> >
> > But then the 'ok will be returned as TEST2::OK, this means that TEST1
> > package has to use symbol-name and intern it
> >
> > This is annoying, how do you solve this issue
>
> You have at least two ways:
>
> - use keywords.
> - export the symbols.
>
>
> Also, in the case of OK, don't use OK.  Use CL:T or CL:NIL !  They're
> made for that (or if you really must, then use :OK).
>
>
>     (in-package :test2)
>     (defun foo (e) (if (eq e :azerty) :ok))
>     (export 'foo)
>     (in-package :test1)
>     (use-package :test2)
>     (foo :azerty)
>     --> :OK
>
> or:
>
>     (in-package :test2)
>     (defun foo (e) (if (eq e 'azerty) T NIL))
>     (export '(foo azerty))
>     (in-package :test1)
>     (use-package :test2)
>     (foo 'azerty)
>     --> T
>
>
> --
> __Pascal Bourguignon__                     http://www.informatimago.com/
> A bad day in () is better than a good day in {}.
>
> _______________________________________________
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>
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