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


"Ara.T.Howard" <ahoward@fattire.ngdc.noaa.gov> schrieb im Newsbeitrag
news:Pine.LNX.4.44.0402190818210.8086-100000@fattire.ngdc.noaa.gov...
> On Thu, 19 Feb 2004, Robert Klemme wrote:
>
> > Date: Thu, 19 Feb 2004 15:43:05 +0100
> > From: Robert Klemme <bob.news@gmx.net>
> > Newsgroups: comp.lang.ruby
> > Subject: Re: proposal: let kind_of take more arguments
> >
> >
> > "Simon Strandgaard" <neoneye@adslhome.dk> schrieb im Newsbeitrag
> > news:pan.2004.02.19.14.25.27.611885@adslhome.dk...
> > > It just hit me.. why not let kind_of? take more arguments?
> > >
> > > irb(main):001:0> x = 3
> > > => 3
> > > irb(main):002:0> x.kind_of?(String)
> > > => false
> > > irb(main):003:0> x.kind_of?(String, Fixnum)
> > > ArgumentError: wrong number of arguments(2 for 1)
> > >         from (irb):3:in `kind_of?'
> > >         from (irb):3
> > > irb(main):004:0>
> > >
> > >
> > >
> > > For instance I have
> > >
> > > def push(choice)
> > >   if choice.kind_of?(Zero) == false and choice.kind_of?(One) ==
false
> >
> > Never compare boolean values to get boolean values.  This can lead to
> > hideous bugs if the method at hand does not return "true" or "false" -
> > especially with languages that have more than one value for either.
>
>
> what do you reccomend (when a case won't do) ?
>
> ...
>   unless choice.kind_of?(Zero) or choice.kind_of?(One)
> ...

Exactly.  Boolean operators are for transformation of boolean values.
Comparison with 'true', 'false', 'nil' or whatever is not appropriate for
the stated reasons.

:-)

    robert