Cond Statement Problems

OK, so I was experimenting with the LOGAND command, just as a learning exercise.

I have tried to build this LISP:

(defun c:BXLister (/ BX_Ans BX_Ent BX_List)
   (initget "Blocks Xrefs")
   (setq BX_Ans (getkword "\nList Blocks or XRefs? [blocks/XRefs] <Both> : "))
   (cond
   ((= BX_Ans "Blocks")
    (setq BX_Ent  (tblnext "BLOCK" T)
          BX_List "Blocks: \n"
    ) ;_  end setq
    (while    BX_Ent
        (if (eq 0 (logand 0 (cdr (assoc 70 BX_Ent))))
        (setq BX_List (strcat BX_List (cdr (assoc 2 BX_Ent)) "\n"))
        ) ;_  end if
        (setq BX_Ent (tblnext "BLOCK"))
    ) ;_  end while
   )
   ((= BX_Ans "XRefs")
    (setq BX_Ent  (tblnext "BLOCK" T)
          BX_List "XRefs: \n"
    ) ;_  end setq
    (while    BX_Ent
        (if (eq 4 (logand 4 (cdr (assoc 70 BX_Ent))))
        (setq BX_List (strcat BX_List (cdr (assoc 2 BX_Ent)) "\n"))
        ) ;_  end if
        (setq BX_Ent (tblnext "BLOCK"))
    ) ;_  end while
   )
   ((/= BX_Ans "XRefs" "Blocks")
    (setq BX_Ent  (tblnext "BLOCK" T)
          BX_List "Blocks & XRefs: \n"
    ) ;_  end setq
    (while    BX_Ent
        (setq BX_List (strcat BX_List (cdr (assoc 2 BX_Ent)) "\n"))
        (setq BX_Ent (tblnext "BLOCK"))
    ) ;_  end while
   )
   ) ;_  end cond
   (alert BX_List)
   (princ)
) ;_  end defun

I intend it to list either Xref or Block depending on the input of the user.

However, its not in fact the logand function I am having problems with - the problem occurs when the user enters to list Xrefs - the program will list blocks AND xrefs.

I think there is an error with the cond statement, but I can't see what

Thanks in advance guys.

Ok,

I have performed the same task in a different manner - posted for everyone's benefit:

(defun c:BXLister (/ BX_Ent BX_BList BX_XList)
   (setq BX_Ent   (tblnext "BLOCK" T)
     BX_BList "Blocks: \n"
     BX_XList "Xrefs: \n"
   ) ;_  end setq
   (while BX_Ent
   (if (eq 0 (logand 0 (cdr (assoc 70 BX_Ent))))
       (setq BX_BList (strcat BX_BList (cdr (assoc 2 BX_Ent)) "\n"))
   ) ;_  end if
   (if (eq 4 (logand 4 (cdr (assoc 70 BX_Ent))))
       (setq BX_XList (strcat BX_XList (cdr (assoc 2 BX_Ent)) "\n"))
   ) ;_  end if
   (setq BX_Ent (tblnext "BLOCK"))
   ) ;_  end while
   (alert (strcat BX_BList "\n" BX_XList))
   (princ)
) ;_  end defun

Lee,

The easiest way to step thru a nongraphical table is with a ( while ) call:

[b][color=BLACK]([/color][/b]defun c:blist [b][color=FUCHSIA]([/color][/b]/ tdef bn al xl bl[b][color=FUCHSIA])[/color][/b]
 [b][color=FUCHSIA]([/color][/b]while [b][color=NAVY]([/color][/b]setq tdef [b][color=MAROON]([/color][/b]tblnext [color=#2f4f4f]"BLOCK"[/color] [b][color=GREEN]([/color][/b]not tdef[b][color=GREEN])[/color][/b][b][color=MAROON])[/color][/b][b][color=NAVY])[/color][/b]
        [b][color=NAVY]([/color][/b]setq bn [b][color=MAROON]([/color][/b]cdr [b][color=GREEN]([/color][/b]assoc 2 tdef[b][color=GREEN])[/color][/b][b][color=MAROON])[/color][/b][b][color=NAVY])[/color][/b]
        [b][color=NAVY]([/color][/b]cond [b][color=MAROON]([/color][/b][b][color=GREEN]([/color][/b]= [b][color=BLUE]([/color][/b]logand [b][color=RED]([/color][/b]cdr [b][color=PURPLE]([/color][/b]assoc 70 tdef[b][color=PURPLE])[/color][/b][b][color=RED])[/color][/b] 4[b][color=BLUE])[/color][/b] 4[b][color=GREEN])[/color][/b]
               [b][color=GREEN]([/color][/b]setq xl [b][color=BLUE]([/color][/b]cons bn xl[b][color=BLUE])[/color][/b][b][color=GREEN])[/color][/b][b][color=MAROON])[/color][/b]
              [b][color=MAROON]([/color][/b][b][color=GREEN]([/color][/b]= [b][color=BLUE]([/color][/b]logand [b][color=RED]([/color][/b]cdr [b][color=PURPLE]([/color][/b]assoc 70 tdef[b][color=PURPLE])[/color][/b][b][color=RED])[/color][/b] 1[b][color=BLUE])[/color][/b] 1[b][color=GREEN])[/color][/b]
               [b][color=GREEN]([/color][/b]setq al [b][color=BLUE]([/color][/b]cons bn al[b][color=BLUE])[/color][/b][b][color=GREEN])[/color][/b][b][color=MAROON])[/color][/b]
              [b][color=MAROON]([/color][/b]T
               [b][color=GREEN]([/color][/b]setq bl [b][color=BLUE]([/color][/b]cons bn bl[b][color=BLUE])[/color][/b][b][color=GREEN])[/color][/b][b][color=MAROON])[/color][/b][b][color=NAVY])[/color][/b][b][color=FUCHSIA])[/color][/b]

  [b][color=FUCHSIA]([/color][/b]princ [color=#2f4f4f]"\nXREF List = "[/color][b][color=FUCHSIA])[/color][/b]
  [b][color=FUCHSIA]([/color][/b]prin1 xl[b][color=FUCHSIA])[/color][/b]
  [b][color=FUCHSIA]([/color][/b]princ [color=#2f4f4f]"\nANONYMOUS BLOCK List = "[/color][b][color=FUCHSIA])[/color][/b]
  [b][color=FUCHSIA]([/color][/b]prin1 al[b][color=FUCHSIA])[/color][/b]
  [b][color=FUCHSIA]([/color][/b]princ [color=#2f4f4f]"\nSTANDARD BLOCK List = "[/color][b][color=FUCHSIA])[/color][/b]
  [b][color=FUCHSIA]([/color][/b]prin1 bl[b][color=FUCHSIA])[/color][/b]
  [b][color=FUCHSIA]([/color][/b]prin1[b][color=FUCHSIA])[/color][/b][b][color=BLACK])[/color][/b]

-David

Fantastic David,

I made things awkward for myself by using the cond before using the while to step through.

I like your LISP - Thanks.

Hi Lee,

Regarding your first code example with the COND, I haven't studied it enough to completely understand what you're doing, but I did notice the line

(/= BX_Ans "XRefs" "Blocks") . My reference says that the NOT EQUAL function is not defined with more than two arguments. This might be a problem. The weird thing is, in the reference manual, the function is written (/= atom atom ...) , suggesting more than two arguments! Typo, I guess.

I was under the impression that the functions:

=, /=, , = could take any number of args.

If you type:

(/= 4 5 6)

in your command line, it returns T.

Thanks for your time though CALCAD.

David,

Just out of curiosity, do you manually assign a different colour to each bracket when you post, or do you have a program do it for you?

I like David's.

Modified output to this:

   (princ "\n   XREF List = ")
  (mapcar 'print xl)
  (princ "\n   ANONYMOUS BLOCK List = ")
  (mapcar 'print al)
  (princ "\n   STANDARD BLOCK List = ")
  (mapcar 'print bl)
  (prin1))

Lee,

My little investigation of the NOT EQUAL function resulted in discovering mistakes or omissions in two of my references and

a surprising (to me) non-standard behavior of this function in Autolisp. You may wish to test your Autocad 2004 to see if it

conforms to the following :

Extract from the Autocad 2008 on-line help file :

.... Returns T if no two successive arguments are the same in value; otherwise nil. If only one argument is supplied, /= returns T.

Note that the behavior of /= does not quite conform to other LISP dialects. The standard behavior is to return T if no two arguments in the list have the same value. In AutoLISP, /= returns T if no successive arguments have the same value; see the examples that follow.

Examples

(/= 10 20) returns T

(/= "you" "you") returns nil

(/= 5.43 5.44) returns T

(/= 10 20 10 20 20) returns nil

(/= 10 20 10 20) returns T

Note : In the last example, although there are two arguments in the list with the same value, they do not follow one another; thus /= evaluates to T.

the (/=) function has always been flakey and the documentation poorly written. I avoid it with multiple arguments it at all costs as that it has very little real world value.

Lee,

I wrote a program that reads .LSP files and formats it into HTML a long time ago. I redid it to output in BBC when CADTutor changed its format some time ago and just did some tweaking on it. I've always thought color coded paraenthisis was a good proof reading tool. Also a good learning tool.

I'm not a big fan of ending comments i.e ); end if

I use them from time to time when developing a very lagre rotuine but omit them in the final editions. -David

Nice one David.

I must say, you are really good at programming.