Compare two entities if same

[paullimapa]

Is there a lisp function that would allow me to compare to see if two Entity Names in both cases retrieved using (car(Entsel)) are refer'g to the exact same object in  a given AutoCAD drawing?

[hak_vz · Accepted solution]

Just compare entity handle (code 5).  Handles are unique to each entity

[paullimapa]

Excellent...thanks for the quick reply and solution.

[devitg]

@hak_vz ,  Handle is unique , and exclusive . 

2 equal entities  have different Handle , but ir are equal 

So there shall be a way to test for equality. 

[Sea-Haven]

Are they 2

Lines

Same layer

Same angle

Same length

Then yes they are the same but located in different parts of the dwg.

[hak_vz]

@Sea-HavenI think @paullimapa  asked for exact same object (entity) and not to compare two objects geometric and other properties. Handle is unique object property that stays  saved in dwg as long as it exist in file, while entity name or 1005 xdata change.

[kpblc2000 · Accepted solution]

(setq a (car (ensel)) b (car (entsel)))

(equal (entget a '("*")) (entget b '("*")))

:?:

[paullimapa]

This is another excellent solution...thanks.

[devitg · Accepted solution]

Hi, kpblc2000 , i do not understand  how, 2 "LIKE THE SAME" can give the same entity name .

Only if you pick at the REALLY same ent it will give T for equal. 

Neither need to compare the ENTGET. just compare a b 

(setq a (car (entsel)))
(setq b (car (entsel)))

(equal a b)

 Will be T if user pick twice at the SAME ent  

Maybe the OP , need to know if the user pick twice at the same ENT.

[paullimapa]

yep, that worked too.

I think my mistake was using the wrong function

I used "=" but that only works for #s

I should be using "equal" which is what works.

Thanks for your input...

[Kent1Cooper]

[never mind]

[Kent1Cooper]

---

@paullimapa wrote:

....

I used "=" but that only works for #s

I should be using "equal" which is what works.

....

---

[Just for future reference, (=) also works with text strings.  And (eq) works as well as (equal) in this case.]

[paullimapa]

you are correct...that's why I've used = so much because it also works with strings.

[paullimapa]

found this thread of another using = instead of equal

https://forums.autodesk.com/t5/visual-lisp-autolisp-and-general/compare-entity-names/td-p/2422897 

[devitg]

My not-twice way 

(SETQ A (CAR (ENTSEL)))


(SETQ OTHER (NOT-TWICE A))


(DEFUN NOT-TWICE  (A / B)

  (SETQ B (CAR (ENTSEL)))

  (IF (EQUAL A B)
    (PROGN
      (ALERT "you pick the same entity")
      (NOT-TWICE A)
      )
    )
  B
  )