Topic: Redefine defun?

[mkweaver]

Is it possible to redefine the defun function?  I would like to redefine defun so I could add a function call at the beginning of each procedure.

[PKENEWELL]

I'm not exactly sure what you mean. If you literally mean changing the "defun" subr to some other name, then no. But you can redefine function names on the fly in AutoLisp. A great example of that is with built in "autoload" function. It writes a stub function that loads the Lisp file associated with the command, then rewrites itself when the lisp file is loaded.

This is pulled from the "acad2024doc.lsp" file showing how it is written. Warning, it's pretty advanced stuff:

Code - Auto/Visual Lisp: [Select]

1. (defun autoload (app cmdliste)
2.   (_autoqload "" app cmdliste)
3. )
4.  
5. (defun autoarxload (app cmdliste)
6.   (_autoqload "arx" app cmdliste)
7. )
8.  
9. (defun _autoqload (quoi app cmdliste / qapp symnam)
10.   (setq qapp (strcat "\"" app "\""))
11.   (setq initstring "\nInitializing...")
12.   (mapcar
13.    '(lambda (cmd / nom_cmd)
14.       (progn
15.         (setq nom_cmd (strcat "C:" cmd))
16.         (if (not (eval (read nom_cmd)))
17.             (eval
18.              (read (strcat
19.                     "(defun " nom_cmd "( / rtn)"
20.                     "(setq m:err *error* *error* *merrmsg*)"
21.                     "(if (ai_ffile " qapp ")"
22.                     "(progn (princ initstring)"
23.                     "(_auto" quoi "load " qapp ") (setq rtn (" nom_cmd ")))"
24.                     "(ai_nofile " qapp "))"
25.                     "(setq *error* m:err m:err nil)"
26.                     "rtn)"
27.                     ))))))
28.    cmdliste)
29.   nil
30. )
31.  
32. (defun _autoload (app)
33. ; (princ "Auto:(load ") (princ app) (princ ")") (terpri)
34.   (load app)
35. )
36.  
37. (defun _autoarxload (app)
38. ; (princ "Auto:(arxload ") (princ app) (princ ")") (terpri)
39.   (arxload app)
40. )
41.  
42. (defun ai_nofile (filename)
43.   (princ
44.     (strcat "\nThe file "
45.             filename
46.             "(.lsp/.exe/.arx) was not found in your search path folders."
47.     )
48.   )
49.   (princ "\nCheck the installation of the support files and try again.")
50.   (princ)
51. )
52.  
53. (defun ai_ffile (app)
54.   (or (findfile (strcat app ".lsp"))
55.       (findfile (strcat app ".exp"))
56.       (findfile (strcat app ".exe"))
57.       (findfile (strcat app ".arx"))
58.       (findfile app)
59.   )
60. )
61.  
62. (defun *merrmsg* (msg)
63.   (princ msg)
64.   (setq *error* m:err m:err nil)
65.   (princ)
66. )
67.  

[JohnK]

I'm not exactly sure what you mean. If you literally mean changing the "defun" subr to some other name, then no. But you can redefine function names on the fly in AutoLisp. A great example of that is with built in "autoload" function. It writes a stub function that loads the Lisp file associated with the command, then rewrites itself when the lisp file is loaded.
...>%

I didn't spend any time looking at the code but that sounds interesting. Is this a new feature (I am still using 2022 at the moment)? The description also sounds just like something I wrote for myself, but I called mine JIT (just in time) load.  Thanks for the tip, I'll try to find some time to look into `autoload`.

REF:
https://www.theswamp.org/index.php?topic=57707.msg610694#msg610694

[JohnK]

Is it possible to redefine the defun function?  I would like to redefine defun so I could add a function call at the beginning of each procedure.

No you can not redefine DEFUN but you can create your own "function builder". I give the basic framework/idea/concept in my Bottom-Up design writeup.
https://www.theswamp.org/index.php?topic=58123.msg613398#msg613398

And a more crazy/wacky idea in a "shortie template" concept post. Works fairly well.
https://www.theswamp.org/index.php?topic=58213.msg614022#msg614022

[PKENEWELL]

I didn't spend any time looking at the code but that sounds interesting. Is this a new feature (I am still using 2022 at the moment)? The description also sounds just like something I wrote for myself, but I called mine JIT (just in time) load.  Thanks for the tip, I'll try to find some time to look into `autoload`.

REF:
https://www.theswamp.org/index.php?topic=57707.msg610694#msg610694

Actually John, the (autoload) function has been a function with AutoCAD as far back as I can remember (At least back to R12). It was never built into the syntax, but was written into the AutoCAD default lisp files, similar to the ai_utils.lsp. It has evolved with AutoCAD to include ARX, VLX, and FAS files, but the basic function was there all along.

[PKENEWELL]

No you can not redefine DEFUN but you can create your own "function builder". I give the basic framework/idea/concept in my Bottom-Up design writeup.
https://www.theswamp.org/index.php?topic=58123.msg613398#msg613398

And a more crazy/wacky idea in a "shortie template" concept post. Works fairly well.
https://www.theswamp.org/index.php?topic=58213.msg614022#msg614022

Great Examples!