If function won't recognize nil value string variable

[Gorra]

Hello,

I have a lisp that extracts values from a csv, writes them to variables and updates existing blocks, which it is thankfully doing. The problem is that it is supposed to skip sub-functions when it encounters blank entries in the csv, but it won't recognize the nil-value variables. I've had it pause and princ the value and type of the variable, which is set to a nil string.

I've tried

(if (eq RES_1_ADDRv nil)

(if (not (eq RES_1_ADDRv nil))

(if (/= RES_1_ADDRv nil)

(if (null RES_1_ADDRv)

(if (not (null RES_1_ADDRv)),

flipping the order of the subsequent then/else as appropriate. Is there an = or /= equivalent function specific to strings that I should be using?

(RES_1_ADDRv is global variable)

Thanks,

Gorra

[ronjonp · Accepted solution]

@Gorra Are you sure that the "nil" values aren't actually empty strings "" ?

(= RES_1_ADDRv "")

FWIW:

;; This
(if (eq res_1_addrv nil))
;; is the same as this
(if (null res_1_addrv))
;; as the same as this
(if (not res_1_addrv))
;; can be simplified to this
(if res_1_addrv)

[Gorra]

@ronjonp 

I think I started out using "", but I'll try the assorted permutations with "" to make sure.

...

Not recognizing as "" either. 

Thanks,

Gorra

[ronjonp]

If you're using the VLIDE, debug using a watch and break point on the variable to see what value it holds.

[Gorra]

I will try it simplified and see if that works

[Gorra]

@ronjonp 

If it can give me that information, I will get VLIDE directly and check. Or is that the one embedded in AutoCad?

Gorra

[ronjonp]

---

@Gorra wrote:

@ronjonp 

If it can give me that information, I will get VLIDE directly and check. Or is that the one embedded in AutoCad?

Gorra

---

The VLIDE/VSCODE is included with the full version of AutoCAD. What are you using to debug now?

[Gorra]

@ronjonp 

If I'm making significant changes the the code I use notepad++, with alerts and princs embedded in relevant places. I open the LISP editor in CAD about a quarter of the time. I didn't realize it could track your variable values, I'll have to start using it more.

It's looking like the simplified if statements are going to work. Having "if [variable]" and nothing after it returning nil isn't what I thought it would do, but I guess it makes sense.

Gorra

[Sea-Haven]

If you use say getstring and press Enter you will get "" a string with nothing in it, a getreal press enter will return nil. 

Not sure if that helps.