[Gambas-user] Referencing an array element with boolean

[Benoît Minisini]

Le 21/06/2014 09:47, Patrik Karlsson a écrit :
> Many years ago when I was programming in Delphi I used to have object
> arrays of size 2 and referencing to the element index with true and false.
> This was very very useful.
>
> It was possible since false=0 and true=+1.
> In Gambas we have false=0 and true=-1.
>
> So now I came up with:
>    Dim sMoods As String[] = ["Sad", "Happy"]
>    Dim bHappiness As Boolean
>
>    Debug CInt(True), Abs(True), Abs(CInt(True))
>    Debug CInt(False), Abs(False), Abs(CInt(False))
>
>    bHappiness = False
>    Debug "bHappiness= "; bHappiness; ": " & sMoods[Abs(CInt(bHappiness))]
>    Debug "bHappiness= "; bHappiness; ": " & sMoods[If(bHappiness, 1, 0)]
>
>    bHappiness = True
>    Debug "bHappiness= "; bHappiness; ": " & sMoods[Abs(CInt(bHappiness))]
>    Debug "bHappiness= "; bHappiness; ": " & sMoods[If(bHappiness, 1, 0)]
>
> 1. Why is Abs(True) True?
>

I think I did that so that TypeOf(Abs(x)) = TypeOf(x). But for boolean, 
it is not very useful. Maybe I should automatically convert Boolean to 
Int in that case, so that Abs(True) = 1 and Abs(False) = 0.

> 2. Which is fastest, Abs(CInt(... or If(... ? I guess that If(... is more
> future proof.

Abs(CInt(True)).

>
> 3. I have a "BoolToIndex" function in a library module but I was thinking
> if it should not be part of the language, to be able to reference in
> a _simple_ way to an array element with a boolean.

No. But you will be able to do Abs(True).

Moreover, Boolean is, by definition, not a good datatype for indexing!

Regards,

-- 
Benoît Minisini