OpenEuphoria

Re: 3.0.3

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> May 12, 2007
• 720 views

Derek Parnell wrote:
> 
> Jeremy Peterson wrote:
> > 
> > Juergen Luethje wrote:
> > > 
> > > global constant
> > >    FALSE = 0,
> > >    TRUE  = not FALSE
> > Why not just
> > 
> > TRUE = 1 
> 
> Because it removes implementation dependancies.
> It is generally accepted <snip> 'FALSE' is implemented as zero; some
> implementations of 'TRUE', use 1, some -1, and some every non-zero value. 
> By defining 'TRUE' as 'not FALSE' it will work with any implementation.

FWIW I prefer this, which I got from someone on this forum:

constant TRUE=(1=1),  -- for Eu, 1 (aka <>0)
         FALSE=(1=0)  -- for Eu, 0

It is succinct and programming-language-independent.

> Also due to a quirk in the way that short-circuit IF evaluations work, it 
> can be made to execute faster when the conditions are separated out ...
> 
> }}}
<eucode>
> global constant
>    FALSE = 0,
>    TRUE  = not FALSE
> 
> global type boolean (object x)
>    if not integer(x) then return FALSE end if
>    if x = FALSE return TRUE end if
>    if x = TRUE  return TRUE end if
>    return FALSE
> end type
> </eucode>
{{{

Crikey! I really (really!) thought that

if integer(x) and (x=FALSE or x=TRUE) then return TRUE end if
    return FALSE

would be faster, but you are right and in my first test some 35% faster.
I thought I understood this, what is this "quirk" am I missing?

Regards,
Pete