[Gambas-user] Question about writing If-clauses

[Jorge Carrión]

"If ... And If ..." is more quick than if ... And...
When a condition is false with if ... And .... If then the following
conditions are not evaluated.
With if ... and ... both conditions must be evaluated before discard

Regards

2018-02-01 8:43 GMT+01:00 Tobias Boege <taboege at gmail.com>:

> On Thu, 01 Feb 2018, Rolf-Werner Eilert wrote:
> > This is from the code snippet Benoit posted yesterday:
> >
> > If InStr(Me.STRING_DELIM, Key.Text) And If hEditor.Column <
> > hEditor.Current.Length Then
> >
> > Do you always repeat "If" after "And", "Or" etc.? And why?
> >
> > I know it (and write it) like If ... And ... Then
> >
> > There is another line where it might make more sense:
> >
> > If Not InsideStringEscape And If String.Mid$(hEditor.Current.Text,
> > hEditor.Column + 1, 1) = Key.Text Then
> >
> > I have to admit, it looks clearer like this, because it says "If Not ...
> And
> > If [Yes] ... Then". But still I am surprised, would it be wrong to write
> it
> > like
> >
> > If Not ... And ... Then
> >
> > Thanks for your insight!
> >
>
> "If ... And ..." and "If ... And If ..." are different. You have to know
> that "And If" is a distinct operator which does short-circuit evaluation
> and the same holds for "Or If" [1].
>
> In the above two specific instances, there is almost no difference between
> And and And-If (except that And-If might be faster since it skips
> evaluating
> the second condition if the first one is already false -- it's a smart AND
> operator, so to speak), but consider code like this:
>
>   If $hProcess And $hProcess.State = Process.Running Then $hProcess.Kill
>   ' vs.
>   If $hProcess And If $hProcess.State = Process.Running Then $hProcess.Kill
>
> The first If will fail with a Null object error in the second condition
> if $hProcess is Null, but the second will work.
>
> Regards,
> Tobi
>
> [1] http://gambaswiki.org/wiki/lang/andif
>
> --
> "There's an old saying: Don't change anything... ever!" -- Mr. Monk
>
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