maxprs

If your only concern would be the variable names, I do have a completely rewritten version of the formula parser that allows for arbitrary (well must start with alpha character and then can contain any alphanumeric character and the underscore) and performs quite a bit better than the NI parser as it does not do all kinds of complicated string reformating on the input string. I also has a clean string to RPN parser so that as long as the string doesn't change one can simply execute the RPN evaluator only, which speeds up the actual calculation of the formula even more. The code was posted long ago here.

Not the only concern, as the application is already written with all the formula nodes.

But sure I'll keep your suggestions under consideration.

Thank you very much

Another possible solution would be to use the Eval Formula Node vi. It's functionally similar as a formula node, but would also have the formula already in string format as an input.

That's a possibility that I already knew.

I gave up because of the modifications needed to adapt the actual formula nodes, and also because of the limitations about the variables name (a, a0... z, z0...). The content of the formula node instead can use any type of strings, i.e. "Energy", "Mass", that makes the formula self explaining.

Okay so I have a working test of what I was talking about with the Pre Build action.  Attached is a project with a VI in it that gets the text of a Formula Node in the development environment.  It also has a string constant that is blank, but before building the EXE it will take the value from the expression node and put it in the string constant.

 

Build the EXE and you'll see that the value of the string constant will change to the value in the expression node.  Not ideal but it can be done with minimal engineering effort, and using all built in tools.

I think that the use of the pre build action is a way to get the info that I need very interesting.

I will do some test to see if it can fit my needs...

Thank you very much for your effort.

Not ideal but the only possible solution then:

 

Create a string constant and copy the script into it and then put the script in a case structure and the string constant in the other case of the structure. Now you can call the VI with a boolean input control to execute the string or retrieve the contents.

 

Requires some discipline to update the string constant when the developer makes changes to the script but is the most straightforward and simple solution if you do not want to go with an external script solutions.

 

Or alternatively if your required scripting formulas are not to complex you might go with the script parser that comes as example in LabVIEW. It is however limited to basic mathematical operations, doesn't support arrays, and interprets the formula each time you execute it.

Yeah, that what I've thought to do as well; the problem is that there will be many formulas in the application, so discipline required is a lot.

On the other hand the limitation of the script parser is not accettable.

I just wonder why NI didn't put a read only property for the formula node where you can get what is written inside as a string.

I don't think any of these methods will work in a build executable. 1) because it is not supported in the runtime engine, 2) because it makes use of the node in 1) and 3) only maybe if you set the VI explicitedly to not remove the diagram when building the executable. The text of the script is part of the diagram like anything else. LabVIEW compiles this in fact into code and then the script text is not really necessary anymore in a build application and therefore gets removed with the diagram. But even if you leave the diagram there it may still not work as a lot of VI scripting operations do not work in the runtime engine since they don't make to much sense anyways when there is usually anyhow no diagram to work on.

Infact, I forgot to tell you that the project is set so the block diagram of the VI where the formula node is contained is not removed.

But it doesn't work anyway.