Re: Nil and false in Lua design

[Thomas Jericke <tjericke@...>]

On 10/14/2013 11:25 AM, Carsten Fuchs wrote:
> Am 14.10.2013 10:32, schrieb steve donovan:
> > On Mon, Oct 14, 2013 at 10:23 AM, Thomas Jericke <tjericke@indel.ch> 
> > wrote:
> > > I think it could be a to high performance hit to have a metamethod 
> > > lookup on
> > > each and every condition or logical expression of a program.
> >
> > True, plus making programs even more confusing...
>
> Well, a __tobool metamethod would just be a typecast, like __tostring.
>
> I'm certainly not feverish about this, but for consistency's sake, I 
> think it would be nice to have either -- or none.   ;-)
I think the main difference is that string converstions themselves are 
often not a simple function, so you can easily accept the overhead of a 
metamethod call. Also in all the programs that are not heavy on text 
manipulation the __toboolean would be called many more times, just think 
of all the while and if statements all over the code.

It wouldn't be a perfomance hit if you only use booleans for conditions 
and logic operations in your code though: if a ~= nil then ... would 
actuall not trigger the metamethod.

--
Thomas