[Gambas-user] Doesn't IF NOT exist? Bug or feature? Or my bad logic?

[Lee McPherson]

Rolf-Werner Eilert wrote:
> Just stumbled over this when trying to implement a small copying function:
>
>    FOR EACH datei IN Dir(opfad, odatei & ".*")
>      IF NOT file.Ext(opfad &/ datei) = "lock" THEN
>        COPY opfad &/ datei TO ziel &/ datei
>        SELECT CASE file.Ext(ziel &/ datei)
>        CASE "fehl", "feldbak", "felder", "notizen"
>          SHELL "chgrp kartei " & ziel &/ datei WAIT
>          SHELL "chmod 660 " & ziel &/ datei WAIT
>        CASE "konto", "kontobak", "ktx", "ktxbak"
>          SHELL "chgrp konto " & ziel &/ datei WAIT
>          SHELL "chmod 660 " & ziel &/ datei WAIT
>        END SELECT
>      END IF
>    NEXT
>
> IF NOT ... = ... THEN
>
> wouldn't copy anything, although only one file has the given extension. 
> When I change this line into
>
> IF file.Ext(opfad &/ datei) <> "lock" THEN
>
> everything runs as expected. Doesn't make sense to me as both ways 
> should mean the same in my understanding of logical NOT (which doesn't 
> mean too much... :-) )
>
> Regards
>
> Rolf
>   
 From the docs, NOT is an operator that makes a boolean it's opposite 
(TRUE turns to FALSE and vice versa) and will also invert each bit in an 
integer.  NOT(11) = -12 because that's what you get when you change 
every bit from on to off and vice versa. 

 From other examples in the docs, if you NOT a string with something in 
it, you will get FALSE.  However, if you NOT an empty string, you will 
get TRUE.