From: Rich Kilmer <rich@...>
Date: 2001-11-30T02:55:42+09:00
Subject: [ruby-talk:26942] Re: overload possible?

Very Cool!

I actually thought about this last night before sleep as 
well...but I was thinking of adding a "types" method to 
Array:

class Array
  def types
    collect {|a| a.type}
  end
end

# Then it looks like:

if __FILE__ == $0
  class Fred
    def hello(*args)
      case args.types
      when [Fixnum, String, Float]
    i, s, f = args
    puts "(Fixnum, String, Float) -> [ #{i}, \"#{s}\", #{f} ]"
    "1"
      when [String, Fixnum]
    s, i = args
    puts "(String, Fixnum) -> [ \"#{s}\", #{i} ]"
    return "2"
      else
    raise TypeError, "Invalid Signature: #{args.types.join(', ')}"
      end
    end
  end

  f = Fred.new
  f1 = f.hello(123, "hello", 123.456)
  f2 = f.hello("hello", 123)
  f3 = (f.hello("abc", "def") rescue $!)

  puts "f1 = #{f1.inspect}  f2 = #{f2.inspect}  f3 = #{f3.inspect}"
end

I like yours because its explicit (you have a Signature class) but
you need a new class (although you also get the "invalid" method
which is nice :).  Of course, my way you are changing an existing
class which may not be great.

Unless Matz wants to add the "types" method to Array...since Array
is being used in method signature structures, this may conform to
his POLS ;-)

Either way...this is great and I am going to use it in my code!

-Rich

> -----Original Message-----
> From: nobu.nokada@softhome.net [mailto:nobu.nokada@softhome.net]
> Sent: Thursday, November 29, 2001 11:35 AM
> To: ruby-talk ML
> Subject: [ruby-talk:26930] Re: overload possible?
> 
> 
> At Thu, 29 Nov 2001 14:05:00 +0900,
> Rich Kilmer <rich@infoether.com> wrote:
> > excellent idea...how about this refactoring...
> 
> I thought up another trick.
> 
> class Signature < Array
>   def invalid
>     TypeError.new("Invalid Signature: #{collect {|a| a.type}.join(', ')}")
>   end
> 
>   def ===(args)
>     length == args.length or return false
>     each_with_index {|t, i| t === args[i] or return false}
>     true
>   end
> end
> 
> if __FILE__ == $0
>   class Fred
>     def hello(*args)
>       case args = Signature[*args]
>       when Signature[Fixnum, String, Float]
> 	i, s, f = args
> 	puts "(Fixnum, String, Float) -> [ #{i}, \"#{s}\", #{f} ]"
> 	"1"
>       when Signature[String, Fixnum]
> 	s, i = args
> 	puts "(String, Fixnum) -> [ \"#{s}\", #{i} ]"
> 	return "2"
>       else
> 	raise args.invalid
>       end
>     end
>   end
> 
>   f = Fred.new
>   f1 = f.hello(123, "hello", 123.456)
>   f2 = f.hello("hello", 123)
>   f3 = (f.hello("abc", "def") rescue $!)
> 
>   puts "f1 = #{f1.inspect}  f2 = #{f2.inspect}  f3 = #{f3.inspect}"
> end
> 
> Nobu Nakada