From: Robert Klemme <shortcutter@...>
Date: 2010-01-29T01:16:06+09:00
Subject: Re: Class with Multi Constrcutor ( initialize )

2010/1/28 Albert Schlef <albertschlef@gmail.com>:
> Gary Wright wrote:
>> On Jan 27, 2010, at 4:14 PM, Albert Schlef wrote:
>>
>>> Cool. Where is "Array#===" documented? I couldn't find it.
>> Unfortunately Array#=== is just the same as Array#==,
>
> So it isn't cool. "when [Integer, Integer]" won't match any integer
> numbers :-(
>
>> There was a somewhat recent thread about changing Array#=== to
>> be an element-wise application of ===, which makes a lot of
>> sense to me.
>
> to me too.

Even if that would not happen you could do this and benefit from a
more efficient approach because tests are constants:

def MultiCheck(*a)
  def a.===(b)
    zip(b) {|x,y| return false unless x === y}
    true
  end
  a.freeze
end

irb(main):023:0> T1 = MultiCheck String
=> [String]
irb(main):024:0> T2 = MultiCheck Fixnum, String
=> [Fixnum, String]
irb(main):025:0> def overload(*a)
irb(main):026:1> case a
irb(main):027:2> when T1
irb(main):028:2> puts "a single string"
irb(main):029:2> when T2
irb(main):030:2> puts a[1] * a[0]
irb(main):031:2> else
irb(main):032:2* raise ArgumentError, "can't %p" % a
irb(main):033:2> end
irb(main):034:1> end
=> nil
irb(main):035:0> overload "foo"
a single string
=> nil
irb(main):036:0> overload 2, "foo"
foofoo
=> nil
irb(main):037:0> overload 2
ArgumentError: can't 2
        from (irb):32:in `overload'
        from (irb):37
        from /opt/bin/irb19:12:in `<main>'
irb(main):038:0>

:-)

Note, the same approach also works with regular expressions as
elements in the MultiCheck Array.

Cheers

robert

-- 
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