From: Srijayanth Sridhar <srijayanth@...>
Date: 2009-04-29T15:29:49+09:00
Subject: Re: Hash#map

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class Hash
   def new_map
       result = self.map do |k,v|
          r = yield v
          [k,r]
       end
       Hash[*result.flatten]
   end
end

a = {}
a[2] = 4
a[3] = 6

b=a.new_map do |v|
   v+2
end

puts b.class
puts b.inspect

yields:

Hash
{2=>6, 3=>8}

Does this help?

Jayanth

On Wed, Apr 29, 2009 at 11:30 AM, Fredrik <fredjoha@gmail.com> wrote:

> Is there any good reason why Hash#map does not give back a Hash (Ruby
> 1.8 but same in 1.9 as far as I know)? I often find myself writing
> these kind of things:
>
> newhash = oldhash.inject({}) { |h,(k,v)| h[k] = some_operation(v); h }
>
> but that doesn't look pretty at all in my opinion. I want to just
> write like this:
>
> newhash = oldhash.map { |k,v| some_operation(v) }
>
> I finally got around to change this behaviour for my own code, but are
> all Ruby users supposed to invent this wheel on their own? Wouldn't it
> be better if Hash#map behaved like this? Or is there something I am
> missing?
>
> class Hash
>  def hashmap
>    self.inject({}) do |newhash, (k,v)|
>      newhash[k] = yield(k, v)
>      newhash
>    end
>  end
> end
>
>
> Regards,
> Fredrik
>
>

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