Vertical Speed

Thanks! Would have been nice being able to declare byte variable. I can see some memory improvement... Maybe on on upcoming CIQ release... Garmin shoud give us more control on this as memory is very limited...

By the way, that's the code I came up with:

class MyClass extends WatchUi.DataField
{
  protected var arrayAltPointer = 0;
  protected var arrayAltPrecision = 60;
  protected var altitudeArray = new [arrayAltPrecision];
  protected var verticalSpeed = 0;

  function initialize()
  {
    var info = Activity.getActivityInfo();
    var currentAltitude = info.altitude == null ? 0 : info.altitude;
      
    for (var i = 0; i < arrayAltPrecision; i++)
    {
	    altitudeArray[i] = currentAltitude;
    }
  }

  function compute(info)
  {
    if (info.altitude  != null)
    {
      var index = arrayAltPointer % arrayAltPrecision;
      var calculatedAltitude = info.altitude - altitudeArray[index];
      altitudeArray[index] = info.altitude;
      
      arrayAltPointer++;
      var indexLastArrayElement = arrayAltPointer < arrayAltPrecision ? arrayAltPointer : arrayAltPrecision;
      verticalSpeed = calculatedAltitude / indexLastArrayElement * 60;
    }
  }
}

yes, because byte arrays the ("b") are arrays. an array of bytes (8 bit values).  That's why you get the error with var1 - it's not an array

Actually not.  With a byte array, each item in the array is 8 bits.  If you want to put a 32 bit value in a byte array, you need to use encodeNumber, where it takes 4 bytes of the array and you can specify the endian and starting offset in the byte array.   So if you put a 32 bit value in a byte array, it would be in ba[0], ba[1], ba[2], ba[3] for example.

with encodeNumber you can also insert 16 bit values (which use 2 bytes).  With decodeNumber you can get the values back, using the offset and endian.

consider this:

var ba=new [4]b;
        System.println("ba1="+ba);
        ba[0]=-1;
        ba[1]=255;
        ba[2]=1000;
        ba[3]=123;
        System.println("ba2="+ba);

an exception is thrown on the lines with ba[2]:

Error: Unhandled Exception
Exception: Number is too large to fit within a byte

if ba[3]=null is used, you get an exception that it's not a number at all;  With ba[2]=0x10, here's the output:

ba1=[0, 0, 0, 0]
ba2=[255, 255, 16, 123]

(you'll see that the sign on ba[0] isn't preserved.)

Here's an example of butting a 32 value in a byte array (big and little endian)

        var num=1000;
        ba.encodeNumber(num, Lang.NUMBER_FORMAT_SINT32, {:endianness => Lang.ENDIAN_BIG});
        System.println("ba3="+ba);
        ba.encodeNumber(num, Lang.NUMBER_FORMAT_SINT32, {:endianness => Lang.ENDIAN_LITTLE});
    	System.println("ba4="+ba);

ba3=[0, 0, 3, 232]
ba4=[232, 3, 0, 0]

Great, but it would be even better if Garmin could allow native byte variable. I'm trying to avoid array as they consume too much memory.

It really is an array of bytes, but referenced with a ByteArray object.  The places I use them is with ble to send/receive a series of bytes.

Per the memory viewer, 15 bytes for the object, and then a byte for each element, so "ba" above in 19 bytes long

if I create a byte array that's [80]b, it''s a total of 95 bytes, and so on. So you can save a bunch of memory if you need an array of values that fit in 8 bits

I don't come up with the same memory usage.

To calculate memory usage, I have started my application and look how much memory was used for each element (<Global>, <Code>, <Data>, etc.).

Then I have added to the code a byte array of 1 element and look at memory usage again.

Finally I have added to the code a byte array of 10 elements and look at memory usage again.

I found that 49 bytes were used for the Array itself + 14 bytes for each element in the Array.

I'm using the memory view in the sim.  Could you post that bit of your code?

Memory Usage intially :

Then, I add this single line of code :

protected var BIG_ARRAY = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]b;

The result is as follow :

1314 bytes more on <Code>
8 bytes more on <Data>
127 bytes more on <Entry Point>

Total of 1449 bytes added (49 bytes for the Array + 14 bytes/element)