Re: symbol-function vs defun question

Ah, you mention at the end:
" The reason for doing this is to be
able to define functions within macros whose names are composed from
its arguments."

To do what you're asking above, you can do:

(defun symb (&rest args)
  "Return an interned symbol of concatenated args, from Paul Graham"
  (values (intern (apply #'mkstr args))))

;; call example-1 for macro below:
(define-my-func first-table second-table)

(defmacro define-my-func (t1 t2)
  `(progn
      ;; maybe some let to be inserted in place at macroexpansion: (let
((table1 (make-hash-table)) (table2 (make-hash-table)))
         (defun ,(symb "DESCRIBE-" t1 "-" t2)
            ;; let's say you want the function for above call to use
keywords too: (print (list :first-table table1 :second-table table2))
            (print (list (intern (string-upcase ,t1) :keyword) table1
(intern (string-upcase ,t2) :keyword) table2)))))


On Sun, Mar 24, 2024 at 9:21 PM Jeff Cunningham <[email protected]>
wrote:

> Greetings.
>
> I have been puzzling over a difference between using SYMBOL-FUNCTION
> and DEFUN within a let binding.  Here's a contrived example that
> illustrates:
>
> (let ((table1 (make-hash-table)) (table2 '(1 2 3)))
>   (setf (symbol-function (intern "DESCRIBE-SOME-TABLES"))
>         (lambda () (print (list :table1 table1 :table2 table2))))
>   (defun a-function () (describe-some-tables)))
>
> When this is compiled the first time, the compiler issues the warning:
>
> ;   Undefined function:
> ;     DESCRIBE-SOME-TABLES
> ;   caught 1 STYLE-WARNING condition
>
> Yet the function works:
>
> (a-function)
> ;; => (:TABLE1 #<HASH-TABLE :TEST EQL :COUNT 0 {1003B80DA3}> :TABLE2 (1 2
> 3))
>
> Compiled subsequent times the warning is gone - presumably as the package
> namespace now knows about the function. But unbind it:
>
> (fmakunbound 'describe-some-tables)
>
> and recompile and the warning is back the first time.
>
> Yet if I use DEFUN there is no such warning:
>
> (let ((table1 (make-hash-table)) (table2 '(1 2 3)))
>   (defun describe-some-tables ()
>     (print (list :table1 table1 :table2 table2)))
>   (defun a-function () (describe-some-tables)))
>
> Why is this? And is there a way to get around it so I can define the
> function using symbol-function? The reason for doing this is to be
> able to define functions within macros whose names are composed from
> its arguments.
>
> Thanks.
>
> -- Jeff
>
>
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