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Re: Scope problem (?) in implementing Design Patterns in Ruby

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RichardOnRails wrote in post #998059:
>

1) Your case statement syntax doesn't work in ruby 1.9.2:

prog.rb:4: syntax error, unexpected ':', expecting keyword_then or ',' 
or ';' or '\n'

You have to use 'then' in place of a colon.

2) Next, I get this error:

prog.rb:67:in `evaluate': uninitialized constant Not::All (NameError)
  from prog.rb:74:in `<main>'

which relates to this code:

class Not < Expression
  def initialize(expression)
    @expression = expression
  end

  def evaluate(dir)
    all = All.new.evaluate(dir)
    other = @expression.evaluate(dir)
    all - other
  end
end

In ruby, constants are looked up like directories and files.  When you 
are inside the Not class (which is a module), the 'directory' you are in 
for constant lookups is the 'Not' directory.  When you write All.new, 
because the name All is not preceded by a directory name, ruby looks in 
the current 'directory' for the constant All.  The current directory is 
Not, so ruby is looking for Not::All, i.e. the 'file' All in the 
'directory' Not.  However, All is not defined inside Not, so you get an 
error.  In fact, there is not constant named All defined anywhere in 
your program.

-- 
Posted via http://www.ruby-forum.com/.

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Scope problem (?) in implementing Design Patterns in Ruby RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> - 2011-05-11 10:15 -0700
  Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-11 12:52 -0500
    Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-11 12:53 -0500
    Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-11 13:37 -0500
      Re: Scope problem (?) in implementing Design Patterns in Ruby RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> - 2011-05-11 18:07 -0700
    Re: Scope problem (?) in implementing Design Patterns in Ruby RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> - 2011-05-11 17:30 -0700
  Re: Scope problem (?) in implementing Design Patterns in Ruby 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-11 14:28 -0500
    Re: Scope problem (?) in implementing Design Patterns in Ruby 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-11 15:23 -0500
      Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-11 15:26 -0500
        Re: Scope problem (?) in implementing Design Patterns in Ruby 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-11 15:45 -0500
      Re: Scope problem (?) in implementing Design Patterns in Ruby 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-11 15:34 -0500
        Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-11 15:48 -0500
          Re: Scope problem (?) in implementing Design Patterns in Ruby RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> - 2011-05-12 08:59 -0700
            Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-12 20:56 -0500
              Re: Scope problem (?) in implementing Design Patterns in Ruby 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-12 21:11 -0500
                Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-12 21:18 -0500
              Re: Scope problem (?) in implementing Design Patterns in Ruby RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> - 2011-05-13 00:28 -0700
                Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-13 09:46 -0500
                Re: Scope problem (?) in implementing Design Patterns in Ruby RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> - 2011-05-13 10:55 -0700
                Re: Scope problem (?) in implementing Design Patterns in Ruby 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-13 12:50 -0500
                Re: Scope problem (?) in implementing Design Patterns in Ruby Steve Klabnik <steve@steveklabnik.com> - 2011-05-13 13:14 -0500
                Re: Scope problem (?) in implementing Design Patterns in Ruby RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> - 2011-05-23 19:24 -0700
              Re: Scope problem (?) in implementing Design Patterns in Ruby RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> - 2011-05-24 20:33 -0700
                Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-25 17:30 -0500
                Re: Scope problem (?) in implementing Design Patterns in Ruby RichardOnRails <RichardDummyMailbox58407@USComputerGurus.com> - 2011-05-27 22:08 -0700
  Re: Scope problem (?) in implementing Design Patterns in Ruby 7stud -- <bbxx789_05ss@yahoo.com> - 2011-05-12 21:20 -0500
    Re: Scope problem (?) in implementing Design Patterns in Ruby David Jacobs <developer@wit.io> - 2011-05-12 21:26 -0500
  Re: Scope problem (?) in implementing Design Patterns in Ruby Ryan Davis <ryand-ruby@zenspider.com> - 2011-05-13 12:29 -0500

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