From: Kevin Ballard <kballard@...>
Date: 2005-10-19T22:41:58+09:00
Subject: Re: Unit testing an each function

ES wrote:
> Whoops, sent too soon! I was going to continue >to say that while this is
> nice, for clarity of expression you might want to >state it this way:
>
>    %w{a long list of words}.collect :length

But then that interferes with the ability to do

  [(1..5), (10..15)].each.each { |i| puts i }

(which was the original point of this exercise) or any other nested
enumerations such as

  [(1..5), (10..15)].collect.collect {|i| i + 1}

Brian Schr�der wrote:
> I'd understand this
> >   %w{a long list of words}.collect.length
> as giving me the length of the return value of collect. Collect
> returns an array so I'd expect the above to return five. Maybe it
> would be better to write
>
> %w{a long list of words}.collect_with :length
>
> where in method missing something like this would happen
>
> [...]

Again, same problem, plus the fact that I don't want to be using
method_missing as it would interfere with any existing method_missing
on the class.

Pit Capitain wrote:
> With the famous
>
>    class Symbol
>      def to_proc
>        lambda { |obj| obj.send self }
>      end
>    end
>
> you can get the same result via
>
>    %w{a long list of words}.map(&:length).map(&:to_s)
>
> I'd bet the Symbol#to_proc is somewhere in Nano.

I find that much harder to read, and it also precludes the possibility
of something like

  (1..100).reject.even?

This, of course, relies on a definition of Integer#even? and having the
reject method wrapped, but that's pretty easy:

  class Integer
    def even?
      (self % 2).zero?
    end
  end
  Enumerable::wrap_meth Enumerable, :reject

Granted, for a single use, you'd probably just want to do

  (1..100).reject { |i| (i % 2).zero? }

rather than defining a new method, but this example is just for
illustration.

Of course, it's really intended for dealing with nested enumerables,
like the [(1..5), (10..15)] example above, but it does simplify very
simple single-enumerable handling.