MSFS20 Reverse Polish Notation

[Lagaffe]

Hi,

Trying to add new functions on my addons, I read a lot of XML scripts of others developpers to learn others things.
Yesterday, I read this kind of code that an author use often in it scripts :

1 (L:VARIABLE_A) if{ "do something" } els{ "do other" }

I rather expected a code of this type with an explicit test like : == or >

1 (L:VARIABLE_B) == if{ "action to do" } els{ "other action"}

As I did not see the meaning of this code, I have read several time the "bible" without finding any answer.
The only explanation is that we simply test that the variable is well equal to 1, the 1 first on the line is only there to remember this fact

My question: Is it this syntax correct ? Something is missing ? Is it a mistake ?
If not that is the signification of the first code (in bold and blue)

 

[Socorrista22198]

Hi, it is correct, it means if the VARIABLE_B exist, I mean, If some other instruction set a value to it, 0, 1, 0.1... what else value.

I'm not an expert, but everything I've learned with RPN is, forget everything else you know about pseudocode xD

 

[Lagaffe]

I don’t think it is a test of the existence of the variable otherwise why do two treatments based on the return value : if{*} else{**}
This lines appear several times in the XML code so I don't think it is an error ... or the author was a bad programmer

 

[rhumbaflappy]

I think it does check for any value other than 0, If true than do this, if false (0) then do that.

 

[kalong]

hope that wasn't me .
I always use simplest code in XML. use C++ for logic, C++ logic easy accepted with my brain.

back to the issue:
maybe he/she still learning and use the power of "copy-paste", as long as it work as intended, move on. my

 

[Lagaffe]

Thanks for your answer. No it is not your code
I think I prefer to use proven and simple code (like my second example) rather than trying this kind of thing ... on which we have several interpretations.

I thought there was a great thing down there, actually I think he just made mistakes and didn’t notice.

 

[Socorrista22198]

@rhumbaflappy is true, means different to 0.

To test your RPN expressions, you can create a very simple testing bench using a Behaviors xml file from any plane. In this example, using the animation open door, if the variable "hola" is different to 0, the animation value is 1, door open.

 

[Lagaffe]

Muchas gracias por su tiempo dedicado ! (mis abuelos eran de las Baleares )

Thanks you very much for your complete answer: I will try tomorow. I use very little the interface of the DEV mod, passing more easily by the command line tools

 

[kalong]

that are different between:

1 (L:VARIABLE_A, enum) if{ "do something" } els{ "do other" }

with this

(L:VARIABLE_A, enum) if{ "do something" } els{ "do other" }

2nd code are correct
if not bolean, usually use:

(L:VARIABLE_A, enum) 2 == if{ "do something" } els{ "do other" }

<!-- or -->

(L:VARIABLE_A, enum) 0 &gt; if{ "do something" } els{ "do other" }

 

[Lagaffe]

Yes, Kalong, I agreed perfectly

PS: I program XML since 2006 so I a not that we can call "a beginner in RPN" but I was very surprised by this syntax that I doen't understand ... and I can’t stand not understanding something