Nil question

ruby-talk
1

Lähettäjä: E S <eero.saynatkari@kolumbus.fi>
Aihe: Re: nil question

> Lähettäjä: E S <eero.saynatkari@kolumbus.fi>
> Aihe: Re: nil question
>
> > Lähettäjä: "David A. Black" <dblack@wobblini.net>
> > Aihe: Re: nil question
> >
> > Hi --
> >
> >
> > > "David A. Black" <dblack@wobblini.net> writes:
> > >
> > >> Hi --
> > >>
> > >>
> > >>> "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. :slight_smile:
> >
> > 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.

[Snip my inanities]

Wow. I'm so dense today no wonder I've had stuff hurling towards me. Wonder if I could patent a caffeine capsule that starts dissolving
after 6-7 hours?

Anyway. Looks like Fixnum and Float define < and >, whereas Bignum
and Complex only define <=>

module MultiComparable
  def <(val)
    val if self.<=>(val) == -1
    false
  end
  def >(val)
    val if self.<=>(val) == 1
    false
  end
end

# Modify the existing units
class FalseClass
  def <(val)
    false
  end
end

class Fixnum; include MultiComparable; end
class Bignum; include MultiComparable; end
class Float; include MultiComparable; end
class Complex; include MultiComparable; end

Would that do it (this is real XP, I don't even have a compiler:)?

E

···

> > On Mon, 31 Jan 2005, Christian Neukirchen wrote:
> > >> On Sun, 30 Jan 2005, Christian Neukirchen wrote: