XML code problem

[Dave_W]

I've added two reference markers to an altimeter.

They will indicate an altitude value based on what the altimeter barometric setting is.

I want them to move only when I change the KOHLSMAN setting.

I made the below test code to see what happens when I change the KOHLSMAN setting. The code doesn't work correctly.

  <Element>
    <Select>
      <Value>
        (A:KOHLSMAN SETTING HG, inHg) 29.91 >= (A:KOHLSMAN SETTING HG, inHg) 29.92 &lt; AND  if{ 50 (>L:100s_ref_marker, enum) }       
        (A:KOHLSMAN SETTING HG, inHg) 29.92 == if{ 0 (>L:100s_ref_marker, enum) }
      </Value>
    </Select>
  </Element>

I load a default flight. The setting is the default 29.92. Instead of 0, the L:Var is set to 50. What have I messed up??

I have found that incrementing and decrementing the Kohlsman setting returns a value with a third decimal
place, e.g. 29.911, so that I won't use (A:KOHLSMAN SETTING HG, inHg) value == after I get past this.

Pressing the B key will set a two-place decimal. In this test case 29.92. The L:Var setting stays set at
50. But, shouldn't 29.92 == work to set the L:Var to 0 in this specific case? Or, is it not changing because
of whatever is wrong with the first line of code?

TIA

 

[vololiberista]

When the sim loads it defaults to 29.92 Also it might be an idea to declare your variable
(L:100s_ref_marker, enum) as zero initially and then only when you move the Kohlsmann knob the value will change.

 

[taguilo]

Pressing the B key will set a two-place decimal. In this test case 29.92.

Actually not. That is a floating point value so we cannot know for certain its internal value; what we see is a representation rounded to the number of decimals used for displaying.
Therefore it is not secure to compare any fp value using == operator. Instead, use an integer version, for example 29.92 100 * int

Tom

 

[Dave_W]

Thanks guys.

Volo: I tried your suggestion. The FSX SDK says that "When a local parameter is first referenced, it is created and its value is set to zero." It didn't make any difference.

Tom: unfortunately for me, what you pointed out is why the first line of my code above works when I thought that it wasn't, in addition to why the == operator should not be used.

I found this thread today http://www.fsdeveloper.com/forum/threads/variable-comparison-and-number-formats.437253/

An idea I got somewhat from what Anthony31 said in post #5, I put this in a tooltip:

%((A:KOHLSMAN SETTING HG, inHg))%!f!

the default 29.92 returns 29.919870.

Edit: I ended up using (A:KOHLSMAN SETTING HG, inHg) 100 * near (>L:FormatKollsman, enum) from an idea I got that Tom mentioned in post #4 of the above referenced thread.

 

[vololiberista]

Thanks guys.

Volo: I tried your suggestion. The FSX SDK says that "When a local parameter is first referenced, it is created and its value is set to zero." It didn't make any difference.

From your code snippet it appeared that you had set the value immediately the variable was called. So try setting to zero or create an if{} based on the assumption that it is zero. It won't do any damage.