From: Robert Dober <robert.dober@...>
Date: 2006-07-21T21:27:24+09:00
Subject: Re: opacity of magic enumerator (was: Re: Using .each with constructors)

------=_Part_114954_4281422.1153484840785
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

On 7/21/06, dblack@wobblini.net <dblack@wobblini.net> wrote:
>
> Hi --
>
> On Fri, 21 Jul 2006, Martin DeMello wrote:
>
> > On 7/21/06, dblack@wobblini.net <dblack@wobblini.net> wrote:
> >
> >> On Fri, 21 Jul 2006, Logan Capaldo wrote:
> >> >
> >> > irb(main):001:0> RUBY_VERSION
> >> > =3D> "1.9.0"
> >> > irb(main):002:0> a, b, c =3D 3.times.map { Object.new }
> >> > =3D> [#<Object:0x2382c8>, #<Object:0x2381d8>, #<Object:0x238070>]
> >>
> >> Interesting....  That reveals that one of the problems with this magic
> >> enumerator thing is that the method names weren't necessarily chosen
> >> with this in mind, and don't work very well.  3.times.map very
> >> strongly does *not* communicate a 0...3 mapping to me.  My first
> >
> > If you think about it, though, the underlying problem is that 3.times
> > passes a parameter into the block, which is what makes 3.times.map
> > {|i| } nonintuitive. The plain 3.times.map {} doesn't suggest a 0...3
> > mapping, but rather an enumerator consisting of three "passes" which
> > map naturally turns into a 3-object array.
>
> I'm not getting the "naturally" part :-)  I mean, of course it's all
> non-natural in a sense, but I just can't seem to get my brain to
> perceive 3.times as returning something that responds to map this way.
>
> Maybe part of the problem is that it suggests an equivalence between:
>
>    [0,1,2].map {}
>
> and
>
>    3.times.map {}


I completely agree, we could easily monkeypatch  Fixnum to deliver
     3.numbers =3D> [0, 1, 2]
or
    3.numbers( :starting =3D> 2 ) [2,  3, 4 ]
or
   3.numbers( :interval =3D> 42 ) =3D> [0, 42, 2*42 ]
I do not like the name, but maybe someone has a better idea?

Cheers
Robert

which makes it seem like 3.times is return an array.  Or something.  I
> don't even know exactly; it just reads very badly to me.
>
> > I predict that this *will* seem intuitive once magic enumerators
> > have been around a while - note that it already reads perfectly as
> > 3.times.collect
>
> I think that if something has to be around for a while to be
> comprehensible, it loses the "intuitive" badge :-)  I'm sure that
> eventually the process of mentally translating it will get faster....
> I guess I'm just used to Ruby semantics not having big gaps, and for
> me, there's a big gap between "3.times.map" and mapping across 0,1,2.
> (I'm not sure about your .collect point; to me that suffers from
> exactly the same problem.)
>
> I'm also still troubled by the rather wide net cast by magic
> enumerators.  I don't think anyone came up with an answer to my
> earlier question: When would you ever need this:
>
>    some_enumerable.map.other_method
>
> ?  If the answer is "never", then I don't think map should return an
> enumerator.
>
>
> David
>
> --
> http://www.rubypowerandlight.com =3D> Ruby/Rails training & consultancy
> http://www.manning.com/black     =3D> RUBY FOR RAILS (reviewed on
>                                      Slashdot, 7/12/2006!)
> http://dablog.rubypal.com        =3D> D[avid ]A[. ]B[lack's][ Web]log
> dblack@wobblini.net              =3D> me
>
>


--=20
Deux choses sont infinies : l'univers et la b=EAtise humaine ; en ce qui
concerne l'univers, je n'en ai pas acquis la certitude absolue.

- Albert Einstein

------=_Part_114954_4281422.1153484840785--