topic Re: If function won't recognize nil value string variable in Visual LISP, AutoLISP and General Customization Forum

If function won't recognize nil value string variable

Gorra — Mon, 25 Mar 2024 22:31:49 GMT

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

Re: If function won't recognize nil value string variable

ronjonp — Mon, 25 Mar 2024 22:48:12 GMT

@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)

Re: If function won't recognize nil value string variable

Gorra — Mon, 25 Mar 2024 22:50:05 GMT

@ronjonp

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

...

Not recognizing as "" either.

Thanks,

Gorra

Re: If function won't recognize nil value string variable

ronjonp — Mon, 25 Mar 2024 22:55:44 GMT

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

Re: If function won't recognize nil value string variable

Gorra — Mon, 25 Mar 2024 22:59:27 GMT

I will try it simplified and see if that works

Re: If function won't recognize nil value string variable

Gorra — Mon, 25 Mar 2024 23:01:47 GMT

@ronjonp

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

Gorra

Re: If function won't recognize nil value string variable

ronjonp — Mon, 25 Mar 2024 23:14:40 GMT

@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?

Re: If function won't recognize nil value string variable

Gorra — Mon, 25 Mar 2024 23:29:46 GMT

@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

Re: If function won't recognize nil value string variable

Sea-Haven — Thu, 28 Mar 2024 04:34:36 GMT

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.