From: Martin DeMello <martindemello@...>
Date: 2003-07-22T17:10:25+09:00
Subject: Re: Case Checks

Robert Klemme <bob.news@gmx.net> wrote:
> When I couldn't sleep this morning, this came across my head:
> 
> class Check
>  def initialize(sym, args)
>    @args=args
>    instance_eval "def ===(obj); obj.#{sym}(*@args); end"
>  end
> 
>  class <<self
>    def create(sym=nil, *args, &bl)
>      if bl
>        def bl.===(obj); call(obj); end
>        bl
>      elsif sym
>        new sym, args
>      else
>        raise "Need either block or symbol with arguments"
>      end
>    end
> 
>    private :new
>  end
> end


Very nice! Here's an extension (untested):

def check(*args, &block)
  checks = args
  checks << Check.create(block) if block
  class << checks
    def ===(obj)
      all? {|i| i === obj}
    end
  end
  checks
end

allowing

case i
  when check(Positive, Div5) {|x| x > 100}
    ...

martin