anchor.diff:  # => 4376500
   ----
   
  -Strings are mutable
  -
  +Strings are mutable:
   [source, ruby]
   ----
   hi = "Hello "
   hi << "world"
   ----
  +The above example is similar to a Java `StringBuilder`.
  +
  +Multiline strings is something I miss in Java, but Ruby's syntax is strange.
  +They are delimited with `%{ ... }` or `%! ... !` or ...:
  +[source, ruby]
  +----
  +multiline = %{
  +First line
  +Second line
  +}
  +----
  +
  +I had hard time understanding the concept of *Symbol*.
  +A symbol is a kind of immutable and unique string which can be used as a constant or as a label.
  +[source, ruby]
  +----
  +color = :red
  +color = :blue
  +----
  
positive.code: 
  ## The good
  
  [source,ruby]
  ----
  a=["one","two","three","four"]
  puts a[1..-2]
  # => two three
  first, *tail = a
  ----
  
  ## The bad
  
  
  ## The odd
  
  Objects have a numeric Id which can be used for reference comparison
  
  [source,ruby]
  ----
  o=Object.new
  
negative.code: 
  One of my 2017 resolutions is to try different languages and see how they compare to Java.
  This is inspired by the https://pragprog.com/book/btlang/seven-languages-in-seven-weeks[7 languages in 7 weeks] book by Bruce A. Tate.
  I don't expect to learn a new language each week though, since it took me several weeks for Ruby.
  
  The first language I've tried is Ruby.
  Ruby was created by Yukihiro Matsumoto in the nineties (like Java).
  