[alexandria-devel] concatenate-symbol

[Attila Lendvai]

> Here's my take:
>
> (defun concatenate-symbol (package &rest arguments)
>   "Returns a symbol whose name is a concatenation of printed representations
> of ARGUMENTS, printed as if by PRINC. If PACKAGE is NIL, the symbol is a fresh
> uninterned symbol. If PACKAGE is T, the symbol is interned in the current
> package. Otherwise the symbol is interned in the package designated by
> PACKAGE."
>   (let ((name (with-output-to-string (s)
>                 (dolist (part arguments)
>                   (princ part s)))))
>     (if package
>         (intern name (if (eq t package) *package* package))
>         (make-symbol name))))
>
> I'm a still bit non-plussed of when
>
>   (concatenate-symbol pkg "FOO-" (incf *my-counter* i) "-DING-" i "-" tail)
>
> would be preferable to
>
>   (format-symbol pkg "FOO-~D-DING-~D-~A" (incf *my-counter* i) i tail)
>
> ...so I assume I am misunderstanding the typical use-cases.

well, the point in my original proposal was to cover most of the (my?)
common usecases with a dwim function that is intuitive and easy to
read:

(concatenate-symbol "FOO" some-symbol "BAR")

therefore adding the package argument makes it kinda pointless, we
should just use format-symbol then. also another requirement that
often comes up for me is to be able to control what should happen if
the symbol already exists and it was not interned by us. i usually
(setf (get symbol 'some-marker-that-it-was-created-by-us) t) and later
check that when the interning is requested again.

all in all, the more i'm thinking about it, the less suitable i find
it in alexandria. i guess people should just roll their own macros for
specific use-cases or use format-symbol.

-- 
- attila

"- The truth is that I've been too considerate, and so became
unintentionally cruel...
 - I understand.
 - No, you don't understand! We don't speak the same language!"
(Ingmar Bergman - Smultronstället)