Re: logical stuff

[Jon Stevens <jo...@latchkey.com>]

on 12/28/2000 10:31 AM, "Geir Magnusson Jr." <ge...@optonline.net> wrote:

> There are a few issues pending that we should talk about.  Some came
> from watching turbine list, some from discussion (thanks, Fedor).
> 
> 1) What do we do about determining if a reference is null in VTL?
> 
> Currently, we can use #if(), but that's misleading - if the reference is
> in the context, is a boolean, and is false, than we get the same result
> as if the thing wasn't in there.  So thats no good.  So we need
> something that is clear about what it does, and what the result means.
> 
> Some suggestions :
> 
> - use something like : #if( $foo == null )
> I like this one, but Fedor noted we might want to keep
> the concept of null out of things, although I think it
> is a keyword in javascript, so it isn't that foreign.

+0. This is my preference, however (and hence the 0 score), what is wrong
with:

#if ( $objectUtils.isNull ($foo) )

I'm afraid that we *might* be venturing into adding a bit to much
programming ability into VTL by adding the ability to check for null.

Also, I would prefer it be all uppercase NULL as it is a constant and stands
out more that way.

> - or #ifdefined( $foo )  or #ifdef( $foo )
> This is trivially easy to do.

-1. It adds confusion with #if. People will wonder why they want to use
either one.

> - or another operator :   #if( ?$foo )

Hell no. No PERL!

> 2)  Should we allow the following aliases for the logicals :
> 
> logical AND : '&&' (current), '&', 'AND', 'and'
> 
> logical OR : '||' (current), '|', 'OR', 'or'
> 
> equality : '==' (current), '=', 'eq' ?
> 
> Since there is little or no chance of offering bitwise operations in
> VTL, this might remove some confusion with designers (if there is any).
> I am indifferent tending to negative on this, as I am so used to them
> being different in Java, C++, C, etc, but for designers, that might not
> be a problem.

-1. I think designers understand && and || and ==. I find that using AND/OR
is annoying and somewhat confusing sometimes. I am also against adding a lot
of "alternative" ways of doing things (in other words, overloading is bad).
Again, this also falls under my dislike of adding NULL.

thanks,

-jon

Re: logical stuff

["Geir Magnusson Jr." <ge...@optonline.net>]

Jon Stevens wrote:
> 
> on 12/28/2000 10:31 AM, "Geir Magnusson Jr." <ge...@optonline.net> wrote:
> 
> > There are a few issues pending that we should talk about.  Some came
> > from watching turbine list, some from discussion (thanks, Fedor).
> >
> > 1) What do we do about determining if a reference is null in VTL?
> >
> > Currently, we can use #if(), but that's misleading - if the reference is
> > in the context, is a boolean, and is false, than we get the same result
> > as if the thing wasn't in there.  So thats no good.  So we need
> > something that is clear about what it does, and what the result means.
> >
> > Some suggestions :
> >
> > - use something like : #if( $foo == null )
> > I like this one, but Fedor noted we might want to keep
> > the concept of null out of things, although I think it
> > is a keyword in javascript, so it isn't that foreign.
> 
> +0. This is my preference, however (and hence the 0 score), what is wrong
> with:
> 
> #if ( $objectUtils.isNull ($foo) )

Nothing really, but then we have to have these utils floating about
where it's a simple thing for VTL to do for us.  VTL already handles
null refs already, in #if(), in rendering, in logicals, in the simple
mathematical ops.

I don't want to change how #if() works.  I just want to clear the fog on
the problem of how to tell if a reference is null.
 
> I'm afraid that we *might* be venturing into adding a bit to much
> programming ability into VTL by adding the ability to check for null.

Except we already do that for other reasons : the 'quiet reference' idea
is one example, although implicitly.

Seems like people need a clear, explicit way to working with references
not in the context.
 
> > - or another operator :   #if( ?$foo )
> 
> Hell no. No PERL!

:)


-- 
Geir Magnusson Jr.                               geirm@optonline.com
Velocity : it's not just a good idea. It should be the law.
http://jakarta.apache.org/velocity