From: Tom Werner <pubsub@...>
Date: 2007-08-07T08:55:26+09:00
Subject: Re: Very weird behaviour of Ruby 1.8.6 with multi-line parenthesis expressions

Michael Hollins wrote:
>
> Are there any interesting uses of
>
>    + x
>
> as a statement on its own, or is it likely that
> it's a programmer error 99 times out 100? If the latter, perhaps it's 
> worth
> the ruby interpreter emitting a warning when it sees such constructs, 
> much
> like the warning you get when you don't use parantheses around 
> argument lists
> in certain situations.
>
> I'm happy to be told that there are valid uses of "+ x". I'm still 
> learning something
> new about ruby every day.
>
> cheers,
> mick
>
>
I've seen it used in DSLs (domain specific languages) built with ruby. 
It can be defined on your own classes like so:

class Foo
  def initialize(x)
    @x = x
  end
 
  def +@
    @x.reverse
  end
end

+Foo.new('foo')
# => "oof"

I don't think I've ever used it in any of my code, but that doesn't mean 
there aren't legitimate uses for it. Anyone else used unary plus for 
something useful?

Tom