OpenEuphoria

Re: "case" or better? (2.6 suggestion mode)

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> Apr 03, 2005
• 489 views

On Sat, 02 Apr 2005 23:09:48 -0800, Al Getz <guest at RapidEuphoria.com>
wrote:

>Very interesting.  Can i ask why you want to have multiple if's
>process the same message?

I'm not sure I understand your question. I suppose I could have
written:

procedure Cancel()
	FaceIdx=InitFaceIdx
	PointIdx=InitPointIdx
	applyFont()
end procedure
function Close()
	isFaceName = faces[FaceIdx]
	if FaceIdx>=5 then
		isPointSize = sizes[FaceIdx][PointIdx]
	end if
	setVisible(PFwin,False)
	return 1
end function
...
 	if msg = WM_CHAR and wParam = VK_ESCAPE then
		Cancel()
		return Close()
 	elsif (msg = WM_CHAR and wParam = VK_RETURN)
 	   or msg = WM_COMMAND then
 		if id = PFcncl then
 			Cancel()
 		end if
 		return Close()
 	elsif msg = WM_CLOSE then
 		return Close()
 	end if
 	return 0

Is that what you meant?


>I think the argument *for* the 'case' statement is to have a single test
>determine
>where to jump in the program so you dont have to wait for 100 elsif's
>to fail before you get to the 101'th elsif.
Any gain is only possible if you restrict the proposed case statement
to dealing with a range of n positive integers 1..n, where n must be
known at compile-time. Otherwise, in terms of performance, a case
statement is doomed to be no faster than a huge if/elsif statement,
especially if you want things like unbounded ranges (eg x>2000) or
default clauses, or be able to deal with things like windows messages,
or the dynamically-generated win32lib control-ids, even if they are
declared as "constants". Theoretically, it is not difficult to
optimise away the repeated loads if consecutive elsif clauses have the
same lhs, although I doubt Rob currently does this. I suspect you are
imagining a performance gain which is not going to materialise.

Regards,
Pete