From: "nikolai.weibull@..." <nikolai.weibull@...>
Date: 2007-08-14T23:29:57+09:00
Subject: Re: Does an Array#apply make any sense at all?

On Aug 14, 2:07 pm, dbl...@rubypal.com wrote:
> Hi --
>
>
>
> On Tue, 14 Aug 2007, Robert Klemme wrote:
> > 2007/8/14, nikolai.weib...@gmail.com <nikolai.weib...@gmail.com>:
> >> Hi!
>
> >> I wanted to write a simple method for comparing two paths on a Windows
> >> system.  My initial algorithm felt very contrived:
>
> >> def same_path?(a, b)
> >>   a, b = [a, b].map{ |p| File.expand_path(p).downcase }
> >>   a == b
> >> end
>
> >> It felt like saving the result from #map and then doing the comparison
> >> shouldn't be necessary.  So I came up with the following solution:
>
> >> class Array
> >>   def apply(method)
> >>     shift.send(method, *self)
> >>   end
> >> end
>
> >> This allowed me to define #same_path? thusly:
>
> >> def same_path?(a, b)
> >>   [a, b].map{ |p| File.expand_path(p).downcase }.apply(:==)
> >> end
>
> >> which, to me, looks a lot nicer.  Array#apply takes a method (in a
> >> symbolic manner) and applies it to its first element, passing the rest
> >> of the elements as arguments to the given method.
>
> >> Any thoughts?  Is Array#apply a method that could potentially have
> >> other uses than my specific example above?
>
> > Your method should be called "apply!" because it's destructive.
>
> I could be wrong, but I think the convention (at least in core Ruby)
> is that ! methods always come in a pair with the non-! version.  I
> don't think there are any cases where there's just a method called m!
> where the ! indicates destructiveness (or other "danger"). All the
> unpaired destructive methods have non-! names.

Ugh.  This was so NOT about whether to call the method Array#apply or
Array#apply!.  I just wrote the absolute shortest solution I could
think of.  I didn't suggest that it was the final version.  Yes,
seeing as how my definition mutates its target, Array#apply! is the
appropriate name.  I simply didn't want to clutter the definition
thusly:

class Array
  def apply(method)
    first.send(method, *self[1..-1])
  end
end

(which sort of begs the question why we don't have Array#rest ;-)

  nikolai