From: furtive.clown@...
Date: 2007-11-13T07:20:00+09:00
Subject: Re: alias_method :tap, :affect

On Nov 12, 4:37 pm, James Edward Gray II <ja...@grayproductions.net>
wrote:
> On Nov 12, 2007, at 3:25 PM, furtive.cl...@gmail.com wrote:
>
>
>
> > On Nov 12, 3:55 pm, James Edward Gray II <ja...@grayproductions.net>
> > wrote:
> >> On Nov 12, 2007, at 2:40 PM, furtive.cl...@gmail.com wrote:
>
> >> I guess I want to see some more examples, because I'm seriously
> >> doubting the usefulness.  The example you showed so far was using it
> >> to create this:
>
> >>     platform_audio_files = audio_stems.map { |f|
> >>        f + "." + audio_ext[platform]
> >>     }.as { |t|
> >>        t + audio_basenames
> >>     }.map { |f|
> >>        File.join(audio_dir, f)
> >>     }
>
> >> instead of:
>
> >>     platform_audio_files = (audio_stems.map { |f|
> >>        f + "." + audio_ext[platform]
> >>     } + audio_basenames).map { |f|
> >>        File.join(audio_dir, f)
> >>     }
>
> >> I don't really understand what the problem is with the second version
> >> that's shorter and easier for me to understand.  If it's the need to
> >> introduce some parentheses into the call chain, we can fix that:
>
> >>     platform_audio_files = audio_stems.map { |f|
> >>        f + "." + audio_ext[platform]
> >>     }.concat(audio_basenames).map { |f|
> >>        File.join(audio_dir, f)
> >>     }
>
> >> So yes, please send more examples as I remain unconvinced.
>
> > It was only a coincidence that you found an Array method which
> > corresponded to the operation in the block, namely Array#concat.  Your
> > example breaks down once the operation is nontrivial --- something
> > more complex than '+'.
>
> > We can also introduce temporaries inside the block without causing
> > distraction in the outer scope.  The purpose of the block chain is to
> > produce a value for platform_audio_files; a flood temporary variables
> > on the same scope obscures this purpose.
>
> My counter argument would be that, if it becomes non-trivial, you're
> trying to be too fancy doing it all in one call chain.  Split it up
> into the few lines of code it needs to be.  Then, if the variables
> and such become significant enough to affect the outer scope, it's
> time to tuck the operation away in some method where it belongs.

If you had only one temporary variable in the block, would you move it
to a method?  I would prefer to keep that temporary inside the #as
block -- it truly improves understandably and readability.  There is
no confusion about what the intent is: we are interested in the
result, not the temporaries.

#as is also used to make function calls prettier:

filename = File.basename(input.map { |t|
   t.gsub(re, "_")
}.join)

filename = input.map { |t|
   t.gsub(re, "_")
}.join.as { |t|
   File.basename(t)
}

I greatly prefer the latter.  I want to chain, chain, chain, and I
don't want pesky prefix-y function calls like File.basename() to cramp
my style.