From: Simon Strandgaard <0bz63fz3m1qt3001@...>
Date: 2003-07-22T06:26:52+09:00
Subject: Re: Proposal: Array#to_h, to simplify hash generation

On Tue, 22 Jul 2003 06:59:13 +0900, Brian Candler wrote:

> On Tue, Jul 22, 2003 at 05:46:35AM +0900, Simon Strandgaard wrote:
>> Important: Hash#append should not overwrite earlier entries.
> 
> Hmm. What should it do then? Raise an exception? h1.update(h2) will
> overwrite corresponding keys in h1, so there is a precedent for collect_into
> working in that way.
> 
> I would rule out, say, automatically promoting a value into an array. It's
> too application-specific. If your application does in fact hold a hash of
> arrays, then I think you'd code your append method accordingly; in other
> cases, the structure may be different (a hash of hashes, say), in which case
> the append method is different.

I were too quick to say that is was important. Of cause you supply another
concat method to #into in order to avoid overwriting earlier entries.

untestted :-)


class Hash 
  def myappend(data)
     key, value = data
     self[key] += value
  end
end

[1, "2", 3].into(Hash.new(Array.new), myappend) {|i| [i.class, i]} 
# {"Fixnum"=>[1, 2], "String"=>["2"]}

Sorry :-)

--
Simon Strandgaard