Bug in Context Help for Formula Express VI?

[RavensFan]

While looking at a recent post on the forums in LabVIEW 2011, I saw a user had a Formula Express VI.  I hovered over it and got this for the context help.

It says the formula is just X1.  But go into it, the dialog box says it is

sqrt(((X1*X1)+(Pos2*Pos2))) - (sqrt((X1*X1)+(Pos1*Pos1))) + X2-Pos1

If the context help is intended to show the formula, shouldn't it show the actual formula?

[johnsold]

I do not think this behavior is new.  While I cannot say for sure, I think I have seen the same thing in earlier versions.

I agree that this behavior is worse than useless - it is misleading.  Either provide the actual formula or instruct to open the dialog.

Lynn

[RavensFan]

I think you're right Lynn as I had just installed LV 2011 in the last couple days, and think I've seen it before then.  I haven't had a chance yet to go through older versions of LV to see how far back it goes.

[Benjamin38]

Ravens - 

I'm not really sure why your program is behaving this way.  I was able to have the Help display ideally and have not been able to find any issue or bug reports on this from the past.  The screen shot I attached is from LabVIEW 2011, I also tried it out on 8.6 and it worked fine there as well.    

[lis@jiang]

Good morning guys,

I checked out this Express VI on LabVIEW 2011, and I took some screenshots of what I see.  Please let me know if what you guys are reporting is something different.  A screencap of what you're doing may be helpful, since we're dealing with express VIs.

1.  When the VI first opens, the formula is X1.  Nothing has been changed, and context help shows this:

2.  When you change the formula to something else, you get something like this (after clicking OK, and re-opening up the SubVI).

3.  However, if you open the calculator and change the equation without clicking OK, the SubVi shows something incorrect, like so:

I'm assuming this 3rd situation is what you're seeing, where the Calculator shows a different equation than the context help.  However, this is because the new equation has not been commited to memory yet, and the context help shows the last known equation.

Again, please let me know if you guys are seeing something different.

Regards,

Lisa

[RavensFan]

Well, it's not my VI.  But the one listed in the first message of this thread.  http://forums.ni.com/t5/LabVIEW/How-do-I-make-a-WhileLoop-inside-a-case-structure-execute-CAn-t/m-p/...

I was trying to help in that thread.  One of the things I tried to investigate is what was the output of the formula VI to explain what the boolean results would be.  I hovered over it and got X1,  I double clicked to go in and see it (since I thought it would be ridiculous to have a VI basically do nothing) and saw it was much more complicated.  I probably then cancelled out from there since I wouldn't want to change it.  (Although now that I've gone back to it after seeing your posts, hitting OK did clean up context help.)

So the question is, how did this user create an Express VI where the context help is wrong?

[Benjamin38]

It's possible that something didn't get saved over properly when the vi was exported.  There isn't a character limitation to the formula description, so the fact that it's a bit long has nothing to do with it.  I'd imagine if the program were saved again and resent this behavior wouldn't be seen. As a plan B, dropping in a new Formula vi node could fix the issue.  

[Darin.K]

This Express VI is almost certainly an XNode under the hood (Icon Style menu instead of View as Icon), so there can be some unusual behavior but I haven't reproduced this one.  The last lingering threat of me using this VI was removed when I saw the terminal locations chosen when viewed as a SubVI.

[GregFreeman]

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@Darin.K wrote:

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Result = X1 = X2?   =Undefined?

[johnsold]

I just saw another example of this. I noted the steps I followed showing both the worng formula and, eventually, the correct one.

A VI posted in this post by Marco Montorsi has an Express Formula VI.  The main VI was developed in LV 8.5.

- I downloaded it from the forum and opened it in LV 2011.  Context help said the formula is X1. The dialog says the formula is 10**((X1-X2)/1.0013).

- I saved the VI in the newer version with a different name. Still X1.

- I used Diagram Disable to get rid of the DAQ Assistant so I could run it on my Mac.  Still X1.

- I opened the formula dialog and clicked OK. Now it shows the correct formula.

Somehow, clicking OK in the dialog box seems to be relevant.  I presume that the orignal develper had to have clicked OK to get the formula in there to start with.

Lynn