From: hadley wickham <h.wickham@...>
Date: 2007-10-16T10:07:14+09:00
Subject: Re: nil.to_i returning zero

On 10/15/07, Rick DeNatale <rick.denatale@gmail.com> wrote:
> On 10/15/07, mortee <mortee.lists@kavemalna.hu> wrote:
> > Gerardo Santana Gómez Garrido wrote:
> > > Chand Perrin wrote:
> > >> What would you expect it to return, and why would you think that should
> > >> be the expected behavior?
> > >
> > > I'd expect the same behavior as FalseClass and TrueClass: undefined method.
> > >
> > > Because if I want 0 would expect or send 0, not nil.to_i.
> > > Because it doesn't make sense to me that nil, which means false also,
> > > can be represented as zero, when zero doesn't mean false, but true.
> >
> > Hmmm. Why would you convert a variable/parameter to int if you want to
> > use it in a boolean context, in the first place?...
> >
> > Do you think that to_i is expected to keep the boolean meaning of
> > anything it's sent to, or throw an exception? I don't see why this would
> > ever be related to each other (to_i and boolean operations).
> >
> > > mortee wrote:
> > >> Well, if you'd like it so much, why not just redefine it in your own
> > >> programs? Everyone else seems to expect it to return 0 instead of being
> > >> hostile by throwing an exception...
>
> In fact, I'm almost ready to go out on the limb and suggest that it
> might be nice if:
>
> class NilClass
>
>    def +(aNumber)
>        aNumber
>    end
>
>    def -(aNumber)
>       0 - aNumber
>    end
>
>    alias_method :*, :to_i
>    alias_method: :/, :to_i
> end
>
> which would allow sequences like:
>
>   a ||= 0
>   a += 1
>
> To be just
>   a += 1

Why is addition so special?  What about multiplication and division?

Really, you probably want nil to be the idempotent element for any
operation (ie. f(a, nil) = a).  But can you implement that?  Probably
not.

Hadley

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