Topic: (vl-prin1-to-string (quote lst)) = str ; or Strings to evaluate

[Grrr1337]

Hi guys,
This task might be like a string manipulation challenge:

I've been reading recently here about vla-SendCommand function and decided to give it a try:

Code - Auto/Visual Lisp: [Select]

1. (vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object)) "CHANGE\n(ssget \"_X\")\n\nP\nC\n1\n\n") ; works

The above sample (to change all objects to color 1) works perfectly, however not in these ways:

Code - Auto/Visual Lisp: [Select]

1. (vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object))
2.   "CHANGE
3.  \n(ssget \"_X\")
4.  \n
5.  \nP
6.  \nC
7.  \n1
8.  \n
9.  \n"
10. ) ; not working
11. (vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object)) "CHANGE \n (ssget \"_X\") \n \n P \n C \n 1 \n \n") ; not working

Soo after that conclusion I decided to try to input the arguments for the vla-SendCommand, by using vl-prin1-to-string with quote/apostrophe combo:

Code - Auto/Visual Lisp: [Select]

1. (vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object))
2.   (vl-string-right-trim ")"
3.     (vl-string-left-trim "("
4.       (vl-prin1-to-string
5.         (quote (CHANGE\n(ssget "_X")\n\nP\nC\n1\n\n))
6.       )
7.     )
8.   )
9. )

BUT the problem is that the above argument string is:

Code: [Select]

"CHANGE\\\\N (SSGET \"_X\") \\\\N\\\\NP\\\\NC\\\\N1\\\\N\\\\N"While I need it to become like:

Code: [Select]

"change\n(ssget \"_x\")\n\np\nc\n1\n\n"Which means:
1. Somehow substituting the "\\\\" with "\"
2. Remove spaces " "around the syntaxes "()"
3. (strcase ... t) the whole string

Similiarly to a technique for action_tile I learned from Lee Mac, while dealing with DCL - where his genious mind created this fragment from his code:

Code - Auto/Visual Lisp: [Select]

1. (action_tile "accept"
2.   (vl-prin1-to-string
3.     '(cond
4.       (   (not (and (distof len) (< 0.0 (distof len))))
5.         (set_tile "error" "Please enter a positive numerical length.")
6.       )
7.       (   (not (and (distof wid) (< 0.0 (distof wid))))
8.         (set_tile "error" "Please enter a positive numerical width.")
9.       )
10.       (   (done_dialog 1))
11.     )
12.   )
13. )

So my end question would be: Is it possible to reproduce the same string result with vl-prin1-to-string + quote/apostrophe combo like Lee did, without getting lost in string characters?
Say if further I'd want incorporate fragments from a code as a string to become argument for the vla-SendCommand.
Also would be nice to hear your oppinions (2+ heads are better than 1).

BTW The best way I figured out ot deal with this particular problem is to create a string list, and apply strcat to it:

Code - Auto/Visual Lisp: [Select]

1. (vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object))
2.   (apply 'strcat
3.     '(
4.       "CHANGE"
5.       "\n"
6.       "(ssget \"_X\")"
7.       "\n"
8.       "\nP"
9.       "\nC"
10.       "\n1"
11.       "\n"
12.       "\n"
13.     )
14.   )
15. )

[roy_043]

Two hints:
1.
Try substituting "\n" with " " in your first experiment. This will explain why your second experiment fails.
2.
Instead of:

Code - Auto/Visual Lisp: [Select]

1. (apply 'strcat '("a" "b" "c"))

You can of course use:

Code - Auto/Visual Lisp: [Select]

1. (strcat "a" "b" "c")

[Grrr1337]

Code: [Select]

(vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object)) "CHANGE (ssget \"_X\")  P C 1  "); works
@Roy:
Ooh, I see now! The double-spaces are substituted with single, and if there are any in the end/start of the list are being removed:

Code: [Select]

_$ (quote (CHANGE (ssget "_X")  P C 1  ))
(CHANGE (SSGET "_X") P C 1)
_$ Therefore some partial string manipulation must be performed (to suit this particular string argument) :

Code: [Select]

(vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object)) ; works
  (vl-string-subst " P" "P"
    (strcat
      (vl-string-right-trim ")"
        (vl-string-left-trim "("
          (vl-prin1-to-string
            (quote (CHANGE (ssget "_X")  P C 1  ))
          )
        )
      )
      "  "
    )
  )
)
Thanks alot!
P.S. I often overthink the stuff I write, so I often forget that a single strcat function could be used instead of apply 'strcat
...this defect of mine is usually caused of too many list manipulations 

[roy_043]

In my first hint I was referring to this as the 2nd experiment:

... however not in these ways:

Code - Auto/Visual Lisp: [Select]

1. (vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object))
2.   "CHANGE
3.  \n(ssget \"_X\")
4.  \n
5.  \nP
6.  \nC
7.  \n1
8.  \n
9.  \n"
10. ) ; not working
11. (vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object)) "CHANGE \n (ssget \"_X\") \n \n P \n C \n 1 \n \n") ; not working

It fails because the characters used to format the code are part of the string that is sent:

Code: [Select]

"CHANGE\n  \n(ssget ...) ..."

[Grrr1337]

Thanks Roy,
I was analysing some codes from marko_ribar and assumed that the "\n" represents ENTER key:

Code - Auto/Visual Lisp: [Select]

1. ; "CHANGE" -> "CHANGE\n" -> "CHANGE\n(ssget \"_X\")" -> "CHANGE\n(ssget \"_X\")\n" -> "CHANGE\n(ssget \"_X\")\n\nP"
2. ; -> "CHANGE\n(ssget \"_X\")\n\nP\n" -> "CHANGE\n(ssget \"_X\")\n\nP\nC" -> "CHANGE\n(ssget \"_X\")\n\nP\nC\n"
3. ; -> "CHANGE\n(ssget \"_X\")\n\nP\nC\n1" -> "CHANGE\n(ssget \"_X\")\n\nP\nC\n1\n" -> "CHANGE\n(ssget \"_X\")\n\nP\nC\n1\n\n"
4. (vla-SendCommand (vla-get-ActiveDocument (vlax-get-acad-object)) "CHANGE\n(ssget \"_X\")\n\nP\nC\n1\n\n") ; works

This was the tracing of the string argument filling I did.