From: Levin Alexander <levin@...>
Date: 2006-02-05T03:43:15+09:00
Subject: Re: Fixnum#to_a

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class Integer
  def encode(restbase = 2, *bases)
    mybases = bases.dup
    n = self
    result = []

    begin
      base = mybases.pop || restbase
      base = n+1 if base < 2

      n, val = n.divmod(base)
      result << val

    end until (n == 0) || (n == -1)
    
    if (missing = bases.size - result.size + 1) > 0
      result.concat [0] * missing
    end
    
    result
  end
end

class Array
  def decode(restbase=2, *bases)
    bases = bases.dup
    result = 0
    factor = 1

    self.each { |a|
      base = bases.pop || restbase
      result += a*factor
      factor *= base
    }
    result
  end
end


if __FILE__ == $0

  require 'test/unit'

  class TestEncodeDecode < Test::Unit::TestCase

    def test_encode
      assert_equal [0], 0.encode
      assert_equal [1], 1.encode
      assert_equal [123], 123.encode(0)
      
      assert_equal [0,1,0,1], 10.encode
      assert_equal [5,4,3,2,1], 12345.encode(10)
      assert_equal [6,1,1163,1], 105246.encode(0,1760,3,12)
      assert_equal [0,0,23,0], 82800.encode(0,24,60,60)
      
      assert_equal [1], -1.encode(2) # ???
      assert_equal [6,6,7,8], -1234.encode(10) # ???
      
      assert_equal [456], 456.encode(1) # invalid base
    end

    def test_decode
      assert_equal 0, [0].decode
      assert_equal 1, [1].decode

      assert_equal 12345, [5,4,3,2,1].decode(10)
      
      assert_equal 82800, [0,0,23,0].decode(0,24,60,60)
      assert_equal 105246, [6,1,1163,1].decode(0,1760,3,12)
    end
      
  end
  
end


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