From: SonOfLilit <sonoflilit@...>
Date: 2007-05-30T22:10:37+09:00
Subject: Re: Introducing the "it" keyword

On 5/30/07, SonOfLilit <sonoflilit@gmail.com> wrote:
> Hi all,
>
> That is a very interesting and educating discussion :)
>
> Lately, I came up with #dump!. What is #dump, you ask? It is a
> solution to my problem with #p :
>
> Let's say that I have the line of code:
>   v = matrix*Vector[1, 1, function(a)] + vector.invert
> Now, let's say that I think I have a bug in there.
>
> Normally, if I'm not into using a debugger (perhaps because that's in
> an inner loop and I want to filter the one buggy run from among 1000),
> I am forced to do this:
>   f_a = function(a)
>   v_i = vector.invert
>   m_v = matrix * Vector[1, 1, f_a]
>   v = m_v + v_i
>   p "debug:", f_a, v_i, m_v, v
> and of course, after I'm done, re-structure the code because it's an
> ugly way of doing things in a language that doesn't use polish
> notation.
>
> Here's my solution:
>
> module Kernel
>   def dump!(message = nil)
>     print " ::: #{caller[1]} ::: "
>     print "#message} ::: " if message
>     puts self.inspect # well, actually I use #to_yaml
>     return self
>   end
>
> and lo!:
>   v = matrix*Vector[1, 1, function(a).dump!("debugging that v
> bug")].dump! + vector.invert.dump!
>   v.dump! # I could put it in the prev line with parens, but that's ugly
> no restructuring needed. This can go anywhere. And in the less messy
> cases, I don't even need to remove those dump! calls, I can just
> redefine dump! to return self silently.
>
> That, IMHO, is "the Ruby Way".
>
> In the same code that made me implement that, I've had many cases that
> call for "it", and used the simpler techniques in this thread to
> overcome it (placing "(a == stuff) and rest_of_expression" within an
> if, using a temp var, etc').
>
> Here's what I'm gonna do now:
>
> module Kernel
>   def it!
>     $sonoflilit_it = self
>   end
>   def it
>     $sonoflilit_it
>   end
> end
>
> return it if (heavy_calc(param, param2, param3.moreheavylifting(param4)).it!
>
> or
>
> it.print if matrix.inverse.it!.is_what_i_want
> nil.it!
>
> There still is the problem of garbage collection. nil.it! solves it
> manually in those critical cases, like it being a large matrix.
>
> An alternative version would be:
>
> module Kernel
>   def it!(key = :it_secret_default_key)
>     $sonoflilit_its[key] = self
>   end
>   def it(key = :it_secret_default_key)
>     $sonoflilit_its[key]
>   end
>   def pop_it(key = :it_secret_default_key)
>     $sonoflilit_its.delete(key) # notice that it returns it. might be useful
>   end
>   def clean_its
>     $sonoflilit_its.clean
>   end
> end
>
> for cases like:
>
> if a.calculation.it!(:a).abs > b.calculation2.it!(:b).real_part
>   puts it(:a).det
> else
>   puts func(it(:b))
> end
> clean_its
>
> While previous examples work without change (though the idiom of
> nil.it! isn't recommended for the nil.it(:sym) case, since the hash
> will still keep a member there and with time it could become memory
> consuming).
>
>
> This is not a general solution, and might look bad to some, but it
> serves me well. Feel free to paste it into your own project.
>
>
> Aur Saraf
>
> On 5/30/07, Charles Oliver Nutter <charles.nutter@sun.com> wrote:
> > dblack@wobblini.net wrote:
> > > The argument from precedent is tricky, though.  I'd say the presence
> > > of $_ and $~ and friends suggests, not that more local globals are
> > > desireable, but that Ruby has reached, and perhaps exceeded, its quota
> > > of them :-)
> >
> > No argument from me :)
> >
> > I still think "it" is a terrible keyword to introduce though.
> >
> > - Charlie
> >
> >
>
>

I take this back, unless someone can come up with a solution ot the
following problem:

def a(x)
  return it if x.abs.it! != 1
  0
end

z = Complex[1, 1]
p it if a(z.conj.it!) # prints 1.414..., not Complex[1, -1]


Aur Saraf