From: Simen Edvardsen <toalett@...>
Date: 2006-09-28T23:52:34+09:00
Subject: Re: New magical version of Symbol.to_proc

On 9/28/06, dblack@wobblini.net <dblack@wobblini.net> wrote:
> Hi --
>
> On Thu, 28 Sep 2006, Robert Dober wrote:
>
> > <snip>
> >>
> >>
> >> >>> (1..10).to_a.to_ss
> >> > => ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10"]
> >> >>> (1..10).to_a.days
> >> > => [86400, 172800, 259200, 345600, 432000, 518400, 604800, 691200,
> >> > 777600, 864000]
> >> >>> [2,'two', :two].classes
> >> > => [Fixnum, String, Symbol]
> >> >>> [2,'two', :two].classes.names
> >> > => ["Fixnum", "String", "Symbol"]
> >> >>> [2,'two', :two].classes.names.lengths
> >> > => [6, 6, 6]
> >> >
> >> > So much happy syntax in one place!
> >>
> >> Actually the reason this is kind of cool is not the syntax but the
> >> semantics.  It's much more expressive than any number of &:->()...
> >> things that have been proposed -- and looks better.  (There may be
> >> some connection there too.)
> >>
> >> I wonder, though, whether it would be too easy for it to trample on
> >> other method names.  I guess that's true of anything -- you'd just
> >> have to make sure you didn't have two conceptions of some plural
> >> thing.
> >
> >
> > I agree, *cool* and *somehow dangerous*, I would very conservatively propose
> > a proxy method, similiar in spirit to BDD's rspec#is
> >
> > %w{the meaning of 42}.map.length => [3, too_long_to_count, 2, 2]
> >
> > or maybe not overload #map without params for that purpose?
>
> I personally dislike "magic dot" stuff like that.  True, it's not
> really magic, since map can return some kind of enumerator that knows
> about the array and is ready to do something to it.  But it still has
> the look and feel of a kind of secret system for communicating what's
> wanted, rather than something that really makes sense when read left
> to right.
>
> That's why I prefer Dr. Nic's plurals thing, though it definitely has
> the disadvantage of entering into murky territority in terms of method
> naming.
>

I like the idea of being able to treat messages like some kind of
object and manipulating stuff with them somewhat like this, so just
yesterday I made a mutated version of Symbol#to_proc, the "first
class" message:

class Message
  def initialize(message, *args)
    @message, @args = message, args
  end

  def call(x, *args)
    x.send @message, *(@args + args)
  end

  def to_proc
    lambda { |*args| call(*args) }
  end
end

if $0 == __FILE__
  # Example
  puts [*0..100].select(&Message.new(:>, 50)).inspect
  puts [*0..100].inject(&Message.new(:+))
  puts %w(Once upon a time).map(&Message.new(:upcase)).inspect
  puts Message.new(:index, /[aeiou]/, -3).call("hello")
  puts %w(1 2 3 4 5).map(&Message.new(:to_i)).map(&Message.new(:class)).inspect
end

$ ruby message.rb
[51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67,
68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84,
85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100]
5050
["ONCE", "UPON", "A", "TIME"]
4
[Fixnum, Fixnum, Fixnum, Fixnum, Fixnum]

The syntax isn't as terse, but it does have the advantage of not
interfering with existing methods (and you could just write a kernel
method as a shortcut if you like).

>
> David
>
> --
>                    David A. Black | dblack@wobblini.net
> Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
> DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
> [1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
> [2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org
>
>


-- 
- Simen