Re: continuing continue - was Re: [patch] continue statement

[Philippe Lhoste <PhiLho@...>]

Glenn Maynard wrote:
> On Sat, Sep 24, 2005 at 01:59:52PM +0100, David Given wrote:
> > I would *love* a continue statement in Lua --- I find myself wanting it 
> > frequently.

Funny, I often use break statements, rarely continue.
Well, both have their uses.

> For that matter, I'd rather like goto, as well, but I probably 
> > shouldn't admit that in public.
>
> There's nothing inherently wrong with goto, used judiciously.  The
> "goto considered harmful" folks are guilty of claiming that a language
> feature is always bad, which is almost always false.
>
> The most obvious way of doing the above with goto is to have five labels,
> interleaved through the cleanup code, which is very messy.

Why is it messy?

>  A nice and
> clean way of doing it, though (in C) is:
>
> 	void *a = NULL, *b = NULL, *c = NULL, *d = NULL;
> 	a = foo();
> 	if(!a) goto error;
>
> 	b = foo();
> 	if(!c) goto error;

Typo... Not important to the discussion.

> 	c = foo();
> 	...
>
> 	if(!e) goto error;
> 	do work;
> 	return;
>
> 	error:
> 	if(a != NULL) destroy(a);
> 	if(b != NULL) destroy(b);
> 	if(c != NULL) destroy(c);
> 	...

Which suppose foo() is returning NULL in case of error...

I kind of like:
void *a = NULL, *b = NULL, *c = NULL, *d = NULL;
a = foo();
if (a == NULL) goto errorA;

b = foo();
if (b == NULL) goto errorB;

c = foo();
...

if (e == NULL) goto errorE;
do work;
return;	// We may want to do through...
...

destroy(c);
errorC:

destroy(b);
errorB:

destroy(a);
errorA:

When possible, I avoid mixing true boolean with NULL/0 values, which you 
do in your cleanup code.

My code avoids tests, which is interesting only in time critical 
applications, I suppose.

IMHO, both codes are OK, your may be better suited to complex destroy cases.

--
Philippe Lhoste
--  (near) Paris -- France
--  http://Phi.Lho.free.fr
--  --  --  --  --  --  --  --  --  --  --  --  --  --