From: Noah Easterly <noah.easterly@...>
Date: 2008-01-08T23:05:00+09:00
Subject: Re: proc to block

On Jan 8, 8:24 am, Rick DeNatale <rick.denat...@gmail.com> wrote:
> On Jan 7, 2008 11:35 PM, Gary Wright <gwtm...@mac.com> wrote:
>
>
>
> > On Jan 7, 2008, at 11:06 PM, L A wrote:
>
> > > Hello all,
>
> > > Is there a way to turn a Proc into a block for the purposes of
> > > methods that yield to blocks?  It's not a necessity as I can always
> > > wrap the Proc in a block, I'm just curious.
>
> > Just prefix the object you want to be passed as a block with '&' in
> > the argument list.
>
> > p = proc { |x| x > 10 }
>
> > [1,5,10,20, 30].select &p
>
> Except that this isn't part of the standard ruby library for 1.8. It
> relies on having a Symbol#to_proc method
>
Wait... what?

No it doesn't.

 [ 1, 5, 10, 20, 30 ].map &:to_a

uses Symbol#to_proc

 p = proc { |x| x > 10 }
 [1,5,10,20, 30].select &p

is standard ruby syntax, even from 1.6:

"If the last argument to a method is preceded by an ampersand, Ruby
assumes that it is a Proc object. It removes it from the parameter
list, converts the Proc object into a block, and associates it with
the method."
(see http://www.ruby-doc.org/docs/ProgrammingRuby/html/tut_methods.html#UD)