11 replies to this topic

[GeekDude]

x := ""
 
MsgBox, % IsFunc("f" (x+1))
MsgBox, % IsFunc("f" (""+1))
 
f1(){
}

 

Code to reproduce the issue

[just me]

x := ""
MsgBox, % "|" . (x+1) . "|"  ; calculated   (results in "" because x is empty)
MsgBox, % "|" . (""+1) . "|" ; concatenated (because the first value is a literal string)

[GeekDude]

O_o I could've sworn that x+1 returned 1. I suppose that the IsFunc() isn't the problem, then. So, why doesn't x+1 == 1?

[VxE]

I believe some time ago, Lexikos tweaked the way AHK interprets operators following a quoted literal string. In the case of ( "#" &var ), the assumption is that the user wants to concatenate 'var's address to a literal string. Since + and - are also unary operators, I guess the same tweak applies.

I.e.(""+1) is treated as ("".(+1)).

[GeekDude]

But why does blankvar+1 == blank, instead of concat or addition treating blankvar as 0?

[just me]

What would you expect as the result of adding 1 to nothing?

 

BTW: It wasn't Lexikos.

[Lexikos]

Best Answer

BTW: It wasn't Lexikos.

 

The behaviour when using blank values with math operators (blankvar+1) is separate to what VxE described (""+1).  VxE is correct.

 

"" &var was the main concern for that change, and "" +1 mostly for consistency.  Before "" +1 was treated as concatenation, it produced an empty string; i.e. because it is an invalid operation, as was "" & n (bitwise-and).

[GeekDude]

a++
b+=1
c:=c+1
MsgBox, % a ", " b ", " c ; 1, 1, Blank

Just me, I thought adding 1 to nothing was 1

[just me]

Lexikos, you're right, I remember now. I 'wasn't amused' about that change.
 
GeekDude, sorry, my question wasn't detailed enough. This behaviour is related only to expressions:
 

Except where noted below, any blank value (empty string) involved in a math operation is not assumed to be zero. Instead, it is treated as an error, which causes that part of the expression to evaluate to an empty string. For example, if the variable X is blank, the expression X+1 yields a blank value rather than 1.

[iPhilip]

a++
b+=1
c:=c+1
MsgBox, % a ", " b ", " c ; 1, 1, Blank

Just me, I thought adding 1 to nothing was 1

 

 

I get the same result. If I initialize all the variables ahead of time, e.g.

a := b := c := 0

I get the expected result.

[GeekDude]

If I initialize all the variables ahead of time

 

That's the point. If I don't have to initialize in most cases, why initialize in some cases?

[iPhilip]

I agree. It doesn't make sense.