DME Distance string.format question

[Delta14Sierra]

I am using a  Goflight GF-166 as a DME which includes the following Lua script...

function Distance1(offset,value)
	if (value <= "100") then
		miles1 = string.format("%3.1f",value)
	else
		miles1 = string.format("%s",value)
	end
	prevswitch = -1 -- updates Distance
end

event.offset(0x0C29,"STR",4,"Distance1") -- DME1 Distance

When less than 100 miles, miles1 displays both miles and tenths/mile (e.g.,   0.5   7.5   10.5   99.9 ), as it should.

However, when more than 100 miles, miles1 displays just the miles as a whole number, but the decimal point remains (e.g., 100.  105.   115. ).

Is there a way to rid of the decimal point altogether when more than 100 miles?

[Delta14Sierra]

I thought had a solution, but after testing, it did not work.

[John Dowson]

On 3/8/2024 at 8:49 PM, Delta14Sierra said:

function Distance1(offset,value)
	if (value <= "100") then

This doesn't make much sense as value is a string, and you cannot use the numeric comparison of '<=' on string values - this will NOT be doing what you think.

What you can do is check if the 4th character is a period or not, e.g.

function Distance1(offset,value)
    if (string.byte(value, 4) == 46) then -- is 4th character a period (46)?
        miles1 = string.sub(value, 1, 3)
    else
        miles1 = value
    end
    prevswitch = -1 -- updates Distance
end

event.offset(0x0C29,"STR",4,"Distance1") -- DME1 Distance

John

[Delta14Sierra]

John,

Thank you so much for that instructional insight which now removes the period when it is the fourth character.

But then I found that my GF-166 display was showing 00.0 - 09.9 when the cockpit DME shows 0.0 - 9.9.

So I applied your insight and included an elseif statement which now also strips the leading zero.

function Distance1(offset,value) -- NM1
	if (string.byte(value, 4) == 46) then -- is 4th character a period (46)?
		miles1 = string.sub(value, 1, 3)
	elseif (string.byte(value, 1) == 48) then -- is leading character a zero (48)?
		miles1 = string.format("%1.1f",value)
	else
		miles1 = value
	end
	prevswitch = -1 -- updates Distance
end

There probably is another way to strip the leading zero, but this replicates the cockpit DME on my GF-166 which is what I was hoping to accomplish.

Thank you for sharing your expertise.

Dan

[John Dowson]

16 minutes ago, Delta14Sierra said:

So I applied your insight and included an elseif statement which now also strips the leading zero.

Ok, but I am surprised this works because here:

16 minutes ago, Delta14Sierra said:

miles1 = string.format("%1.1f",value)

value is a string and you are treating it as a number. Maybe it is implicitly converted, but would be better to just use strings, i.e.
     miles1 = string.sub(value, 2, 4)

24 minutes ago, Delta14Sierra said:

Thank you for sharing your expertise.

No problem,

John