Re: if-then-no-else Programming

[Dennis Lee Bieber <wlfraed@ix.netcom.com>]

On Mon, 18 Apr 2016 19:24:51 -0700, csampson@inetworld.net (Charles H.
Sampson) declaimed the following:

>
>He says that there's a move to ban the use of the else-statement. The
>preferred approach is to execute the else-part first, then change the
>effect if the if-condition is satisfied. For example:
>
	A "move" where?

>   Variable := 3;
>   if <condtion> then
>      Variable := 1;
>   end if;
>

	Sure wouldn't work anywhere where the alternatives have side-effects

	if New_Record then
		Insert_Record(data);
	else
		Replace_Record(data);
	end if;

vs

	Replace_Record(data):	-- what if there isn't a record?
	if New_Record then
		Insert_Record(data);
	end if;


	And probably is not recommended if (for simple assignment) the target
is a volatile object -- like GPIO pins accessed via a mapped register. One
wouldn't want to trigger some state that isn't really valid.

	if not Walk then
		Walk_Signal = value_of_dont_walk_lights;
	else
		Walk_Signal = value_of_walk_lights;
	end if;

vs

	Walk_Signal = value_of_walk_lights;
	if not Walk then
		Walk_Signal = value_of_dont_walk_lights;
	end if;

	Would you really want the cross-walk lights to flicker "walk" when
determining they should be "don't walk"? {Yes, it's an artifical example,
but still...}
	

-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/