From: ptkwt@... (Phil Tomson)
Date: 2004-04-08T02:24:18+09:00
Subject: Re: New variable types and assorted lunacy

In article <opr53haaupxses1n@news.elisa.net>, T.Oakley <root@127.0.0.1> wrote:
>On Wed, 07 Apr 2004 15:34:38 GMT, gabriele renzi
><surrender_it@remove.yahoo.it> wrote:
>
>> il Wed, 07 Apr 2004 12:40:34 +0300, "T.Oakley" <root@127.0.0.1> ha
>> scritto::
>>
>>> Hello!
>>>
>>> I'm more or less a newcomer to Ruby ("found" it 4 days ago).
>>> Having mostly dealt with functional/procedural
>>> languages in the past, I'm having a little trouble adjusting to
>>> the OO-paradigm, but nevertheless, Ruby's got me hooked.
>>
>>
>> welcome!
>
>Thank You, I've been enjoying my stay so far :)
>
>>> Anyhow, here's the problem:
>>>
>>> Can create a class that extends the existing variable types?
>>
>> sure and you can even override the default behaviour for existing
>> ones.
>>
>> <snipeed code>
>>
>> You can't ovverride = sorry. It's not a message so we are stuck with
>> stupid accessors :)
>
>Ahh, well, I guess that's something I'll have to live with. Or hack my
>way around it.
>
>> it seem to me you just want a circular array or range, with a cursor.
>> Am I wrong?
>
>Not an array, no, just an Integer. So that if I type, say
>
>aNumber = Wrapped.new(1..3)
>
>the variable aNumber would only get values that === 1..3
>So, for example if aNumber was 1 and I added 3 to it, it would == 1, and
>if I added 4, it would == 2 and so on. It just wraps around. _Why_ do I
>want this? Why not? :) I'm just trying to see what I can and can't do.

You want some sort of n-ary (ternary in this case) type.

Why not do something like:


class OutOfRangeException < Exception
end

class Nary
  attr_accessor :value
  def initialize(range,value=range.first)
    @range = range #should be a range
    check_value(value)
    @value = value
  end

  def assign(value)
    check_value(value)
    @value = value
  end

  def to_i
    @value.to_i
  end

  def to_s
    @value.to_s
  end

  private
  def check_value(value)
    if value < @range.first || value > @range.last
      raise OutOfRangeException, "value must be between #{@range.first}\
                                  and #{@range.last}"
    end
  end
end

ternary = Nary.new(0..2)
puts "value is: #{ternary}" #=> 0
ternary.assign(2)  
puts "value is: #{ternary}" #=> 2
ternary.assign(22) #=> Raises OutOfRangeException "value must be between
                                                   0 and 2" 
binary = Nary.new(0..1)


I'm developing some Ternary Logic classes for a Quantum Computing class 
(as in course - the word 'class' has two meanings in this sentance :)  
I'm taking that basically do what I've shown here (in addition they have 
+,- modulo N operators defined for the class).

Phil