=> "Hello"

1.9.3p125 :028 > -a

NoMethodError: undefined method `-@' for "Hello":String

from (irb):28

from ~/.rvm/rubies/ruby-1.9.3-p125/bin/irb:16:in `'

1.9.3p125 :029 >

1.9.3p125 :029 > def a.-@;downcase;end;

1.9.3p125 :036 > a
=> “Hello”
1.9.3p125 :037 > -a
=> “hello”
1.9.3p125 :038 >

 #!/usr/local/ruby/bin/ruby

 class String

 def -@

 downcase

 end

 def +@

 upcase

 end

 def ~

 # Do a ROT13 transformation - http://en.wikipedia.org/wiki/ROT13

 tr 'A-Za-z', 'N-ZA-Mn-za-m'

 end

 def to_proc

 Proc.new { self }

 end

 def to_a

 [ self.reverse ]

 end

 end

 str = "Teketa's Blog is GREAT"

 puts "-#{str} = #{-str}"

 puts "+#{str} = #{+str}"

 puts "~#{str} = #{~str}"

 puts "#{str}.to_a = #{str.to_a}"

 puts %w{a, b}.map &str

 puts *str

+Teketa's Blog is GREAT = TEKETA'S BLOG IS GREAT

~Teketa's Blog is GREAT = Grxrgn'f Oybt vf TERNG

Teketa's Blog is GREAT.to_a = ["TAERG si golB s'atekeT"]

Teketa's Blog is GREAT

Teketa's Blog is GREAT

TAERG si golB s'atekeT