From: Robert Klemme <bob.news@...>
Date: 2004-02-20T20:21:10+09:00
Subject: Re: proposal: let kind_of take more arguments


"Simon Strandgaard" <neoneye@adslhome.dk> schrieb im Newsbeitrag
news:pan.2004.02.19.15.25.31.227855@adslhome.dk...
> On Thu, 19 Feb 2004 16:14:13 +0100, Robert Klemme wrote:
> > "Simon Strandgaard" <neoneye@adslhome.dk> schrieb im Newsbeitrag
> >> On Thu, 19 Feb 2004 15:43:05 +0100, Robert Klemme wrote:
> >> >
> >> > Why don't you just do
> >> >
> >> > def push(choice)
> >> >   case choice
> >> >     when Zero, One
> >> >       @choices << choice
> >> >     else
> >> >       raise ArgumentError, "got #{choice.class}"
> >> >   end
> >> > end
> >>
> >> a switch statement.. easier to read.
> >> However I like to do bailout as soon as possible,
> >> raising ArgumentError this late may make confusion.
> >
> > What do you mean by "late"?  Do you mean that the line with "raise"
stands
> > below the actual operation.  Didn't think of that, but yes, it might
be
> > confusing.  OTOH, if you can read "case" then it's not so difficult,
is
> > it?
>
> It isn't clear at first sight when the method bailouts, and if
> the switch statement spans over many lines, then its not visible at all
> that its capable of raising exceptions.
>
> Kind_of? similar to bouncer pattern, see
> http://www.rubygarden.org/ruby?BouncerPattern

I see, you want to save the extra method check_arg_xyz().  :-)

>
> >>
> >> Confusion :-)
> >
> >
http://lyricsheaven.topcities.com/survey_d_k_bestanden/ELO.htm#confusion
>
> :-)
>
>
> >> > def Object#kind_of_any?( *classes )
> >>
> >> Yes thought of this.. which maked me propose this idea.
> >
> > I'm wondering though whether it's worth the effort.  When using duck
> > typing, you don't need kind_of? anyway.
> >
> > Btw, I had another idea:
> >
> > PUSH_ALLOWED = {Zero, One}
> >
> > def push(choice)
> >   raise ArgumentError, "got #{choice.class}" unless
> > PUSH_ALLOWED[choice.class]
> >   @choices << choice
> > end
>
> Good idea, but gives a complex impression at first sight.

Really?  PUSH_ALLOWED[choice.class] looks pretty much like a method call
to me...  And it's blindingly fast even for large amounts of classes.
Well, I guess it's a matter of taste then...

You could also use a Set for this like in

require 'Set'
PUSH_ALLOWED = Set.new([Zero, One])

def push(choice)
  raise ArgumentError, "got #{choice.class}" unless
    PUSH_ALLOWED.include? choice.class

  @choices << choice
end

Did I say there are tons of ways in Ruby?  :-))

> > Of course there is a subtle difference since this does not take sub
> > classes into consideration.  But other than that, it should be
faster -
> > especially if you have more classes that shoule be checked.
>
> Im in the make it work phase.
>
> There is 3 phases:
> 1)  make it work
> 2)  make it right
> 3)  make it fast   ;-)

:-)))

Have fun!

    robert