From: Robert Klemme <bob.news@...>
Date: 2004-02-20T20:20:17+09:00
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.

>     raise "got #{choice.class}"
>   end
>   @choices << choice
> end
>
>
> It could turn into
>
> def push(choice)
>   unless choice.kind_of?(Zero, One)
>     raise "got #{choice.class}"

ArgumentError is a good choice here. :-)

>   end
>   @choices << choice
> end

Why don't you just do

def push(choice)
  case choice
    when Zero, One
      @choices << choice
    else
      raise ArgumentError, "got #{choice.class}"
  end
end

or

def push(choice)
  raise ArgumentError, "got #{choice.class}" unless [Zero,
One].map{|cl|choice.kind_of? cl}.any?
  @choices << choice
end

or

class Object
  def kind_of_any?( *classes )
    classes.each{|cl| return true if kind_of? cl}
    false
  end
end

Then:

def push(choice)
  raise ArgumentError, "got #{choice.class}" unless
choice.kind_of_any?(Zero, One)
  @choices << choice
end

Regards

    robert