From: ara.t.howard@...
Date: 2007-03-25T00:44:20+09:00
Subject: Re: Hash#map_pairs

On Sun, 25 Mar 2007 jeff_alexander_44@yahoo.com wrote:

> class Hash
>   def map_pairs
>      result = Array.new
>      self.each_pair { |k, v|
>         result << yield(k, v)
>      }
>      result
>   end
> end
>
> h = {
>   "a" => "x",
>   "b" => "y",
> }
> puts h.map_pairs { |k, v| "#{k} => #{v}" }.join(", ")
>
> I was surprised to discover there was no Hash#map_pairs.  I have found
> that chaining transformations is usually better than the
> iterative/imperative style implied by Hash#each_pair.
>
> On second thought, it looks like this does the same thing:
>
> puts h.to_a.map { |k, v| "#{k} => #{v}" }.join(", ")
>
> But this fails to convey the programmer's idea in the same way that
> map_pairs does.  It is also needlessly inefficient, using a whole
> extra temp array.

harp:~ > cat a.rb
class Hash
   def map_pairs
      result = Array.new
      self.each_pair { |k, v|
         result << yield(k, v)
      }
      result
   end
end

h = {
   "a" => "x",
   "b" => "y",
}

puts h.map_pairs { |k, v| "#{k} => #{v}" }.join(", ")
puts h.map{ |k, v| "#{k} => #{v}" }.join(", ")         ###  ;-)


harp:~ > ruby a.rb
a => x, b => y
a => x, b => y


-a
-- 
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- the dalai lama