Variable Initialization with postfix

[wilkster]

; Below will flag a warning about index not being assigned a value
dummyFunction1() {
someArray := Array()
index++ := someArray.Length
}
; Below works fine
dummyFunction2() {
someArray := Array()
index := someArray.Length
}

Either is valid syntax wise

[RaptorX]

Autohotkey v2 will throw a warning with the first function.

You must assign a number before using the ++ operand.

index := 0
Index++ ; all is good
Msgbox index

On the other hand:

index++ ; this will get a warning
Msgbox index

Try it. :)

So the lexer is correctly warning you of the problem.

If it doesn't it is really unexpected for me because everything in the documentation is clear about trying to use empty variables.

[sousvideonlow]

Yes it seems for good reason that version 2 requires variables to be explicitly declared before we can perform any arithmetic function on them.

[wilkster]

Being a postfix operator isn't:
index++ := someArray.Length
the same as
index := someArray.Length + 1
or
index := someArray.Length
++index

So it is initialized, then incremented
Seems to work that way in AHK V2 anyhow (C works that way as well as I recall)

[RaptorX]

I just tried Your examples on v2 and I do not get a warning when running the code which is highly unexpected.

So you are right, assignment seems to happen before the increment which is very weird looking at how the code is read from left to right 😆

[rebornsick]

Seems like I have the same issue. Every first variable that WingetPos/MouseGetPos asked get a warning. This showcase from documentation have 5 warnings:

EWD_MoveWindow(*)
{
    CoordMode "Mouse"  ; Switch to screen/absolute coordinates.
    MouseGetPos &EWD_MouseStartX, &EWD_MouseStartY, &EWD_MouseWin
    WinGetPos &EWD_OriginalPosX, &EWD_OriginalPosY,,, EWD_MouseWin
    if !WinGetMinMax(EWD_MouseWin)  ; Only if the window isn't maximized 
        SetTimer EWD_WatchMouse, 10 ; Track the mouse as the user drags it.

    EWD_WatchMouse()
    {
        if !GetKeyState("LButton", "P")  ; Button has been released, so drag is complete.
        {
            SetTimer , 0
            return
        }
        if GetKeyState("Escape", "P")  ; Escape has been pressed, so drag is cancelled.
        {
            SetTimer , 0
            WinMove EWD_OriginalPosX, EWD_OriginalPosY,,, EWD_MouseWin
            return
        }
        ; Otherwise, reposition the window to match the change in mouse coordinates
        ; caused by the user having dragged the mouse:
        CoordMode "Mouse"
        MouseGetPos &EWD_MouseX, &EWD_MouseY
        WinGetPos &EWD_WinX, &EWD_WinY,,, EWD_MouseWin
        SetWinDelay -1   ; Makes the below move faster/smoother.
        WinMove EWD_WinX + EWD_MouseX - EWD_MouseStartX, EWD_WinY + EWD_MouseY - EWD_MouseStartY,,, EWD_MouseWin
        EWD_MouseStartX := EWD_MouseX  ; Update for the next timer-call to this subroutine.
        EWD_MouseStartY := EWD_MouseY
    }
}

Every first "X" like &EWD_MouseStartX &EWD_OriginalPosX &EWD_MouseX &EWD_WinX warned not being assigned a value.

[wilkster]

@rebornsick Yes, similar issue,
WinGetPos &EWD_WinX, &EWD_WinY, , , EWD_MouseWin
Will flag a warning, where
WinGetPos(&EWD_WinX, &EWD_WinY, , , EWD_MouseWin)
Will not

[wilkster]

Perfect, thank you!