From: Joel VanderWerf <vjoel@...>
Date: 2009-07-06T03:47:25+09:00
Subject: Re: to_proc and Proc/block conversion with &

David A. Black wrote:
> How odd. I wonder what the point of that is. I'd rather be warned if I
> write Proc.new without a block, than have it default to the code
> block.

Maybe it should be deprecated in practice. It's not apparent what's 
going on, and rdoc can't pick it up (I presume?). It's usually better to 
be more explicit using 'def foo(&b)' or yield.

The only use I can think of for this feature[1] is if you want to 
conditionally instantiate the Proc, as in:

   def defer time
     if time < Time.now
       yield
     else
       pr = Proc.new
       # store pr somewhere and schedule it for execution
     end
   end

[1] ri Proc.new
-------------------------------------------------------------- Proc::new
      Proc.new {|...| block } => a_proc
      Proc.new                => a_proc

      From Ruby 1.8
------------------------------------------------------------------------
      Creates a new Proc object, bound to the current context. Proc::new
      may be called without a block only within a method with an
      attached block, in which case that block is converted to the Proc
      object.

         def proc_from
           Proc.new
         end
         proc = proc_from { "hello" }
         proc.call   #=> "hello"

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407