Understanding Choice dialogue, + and ++

[Mauro]

I'm trying to understand how choice selection, + and ++ works; from the documentation:

To number +
An unary prefix operator that returns the operand converted to a number; +"2" returns 2, +"0xFF" returns 255.

To text ++
An unary prefix operator that returns the operand converted to text; ++2 returns "2".

I made a Choice dialog with the index saved in a variable test, then tried logging:

test + 1 = NaN, so test content isn't a number
+test + 1 = NaN; if test isn't a number, why +test added to a number gives NaN?
++test + 1 = 2; if ++test is text, why it can be added to a number to give a number?

[Henrik "The Developer" Lindqvist]

As the documentation say, "Note! The selected indices/keys output variable is assigned an array even when only a single choice is possible. To get the first or single choice index/key use the subscript operator, e.g.: selected[0] or choices[selected[0]]."

So you should probably do: test[0] + 1

[Mauro]

Thanks, I missed that, it works. Why though + and ++ work like that in this case? Given test + 1 gives NaN, I'd have guessed +test + 1 to be a number, and not ++test + 1, since ++test being a text I thought that it would give NaN in a sum.

[Henrik "The Developer" Lindqvist]

+A is for converting A to a number, but an array can't be converted to a number thus resulting in NaN.

A + B is only for addition, adding array + 1 is invalid since see above.

++A is for converting A to text.

A ++ B is only for string concatenation.

[Mauro]

Then why if test[0] = 1 (only element) then ++test + 1 = 2? Seems like "Convert to text an array containing only 1 and add 1, the result is 2".

[Henrik "The Developer" Lindqvist]

1. ++test will convert the array to text, e.g. [ "1", "2" ] to "12" or [ "1" ] to "1"
   
2. A + B will convert each operator to a number, A to 1 and B to 1, then
   
3. 1+1 = 2
   

[8li...@gmail.com]

sometimes it is easier to look at an example flo  in the  community 

ב-יום חמישי, 29 בספטמבר 2022 בשעה 00:05:26 UTC+3, Mauro כתב/ה: