> Lähettäjä: E S <eero.saynatkari@kolumbus.fi>
> Aihe: Re: nil question
>
> > Lähettäjä: "David A. Black" <dblack@wobblini.net>
> > Aihe: Re: nil question
> >
> > Hi --
> >
> > On Mon, 31 Jan 2005, Christian Neukirchen wrote:
> >
> > > "David A. Black" <dblack@wobblini.net> writes:
> > >
> > >> Hi --
> > >>
> > >> On Sun, 30 Jan 2005, Christian Neukirchen wrote:
> > >>
> > >>> "William James" <w_a_x_man@yahoo.com> writes:
> > >>>
> > >>>> Sam Roberts wrote
> > >>>>> In ruby, zero and empty strings are true
> > >>>>
> > >>>> Since 0 is true, you should be able to do this in Ruby:
> > >>>>
> > >>>> puts "yes" if -5 < x < 9
> > >>>>
> > >>>> The phrase '-5 < x' should yield the value of x instead of true.
> > >>>> That's the way it actually works in the Icon programming language.
> > >>>> But we have to use the klunky
> > >>>>
> > >>>> puts "yes" if -5 < x and x < 9
> > >>>>
> > >>>
> > >>> Erm, say, x is -16:
> > >>>
> > >>> (-5 < x) < 9
> > >>> (-5 < -16) < 9
> > >>> -5 < 9
> > >>> -5
> > >>>
> > >>> -5 is true, probably not what you want.
> > >>
> > >> But -5 < -16 is not true, so it wouldn't get that far. (I assume
> > >> William means it should return x if the expression is true, false
> > >> otherwise.)
> > >
> > > So false is bigger than 9? Math books will need to be rewritten. :-)
> >
> > I assume the expression would short-circuit once one of the
> > sub-expressions returned false, since
> >
> > x < y < z
> >
> > cannot be true unless x < y. So there would never be a false < z
> > comparison.
>
> So...
>
> class Numeric
> alias :old_lt :<
> alias :old_gt :<
>
> def <(val)
> val if self.old_lt val
> false
> end
>
> def >(val)
> val if self.old_gt val
> false
> end
> end
>
> >> x = 5
> >> puts 4 < x < 6
> => 5
> >> puts 6 < x < 7
> => false
>
> ?
Stupid webmail. Fixnums and Numerics probably just use <=> and
<, > from Comparable instead, so this'd require changes to the
core there. Also:
class FalseClass
def <(val)
false
end
end
# And this...
>> x = 5
>> puts 4 < x < 6
# ...should of course return:
=> 6 # or 'true' in a conditional.
> > David
E