From: Daniel N <has.sox@...>
Date: 2006-12-07T13:55:39+09:00
Subject: Re: [GOLF]: partitioning an array

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On 12/7/06, Max Muermann <ruby@muermann.org> wrote:
>
> Take an array of objects and partition it into subarrays, based on
> some arbitrary property of the objects. I would use this for example
> for generating a report of purchase orders and grouped by week, month,
> year, approximate value, etc.
>
> The idea is similar to Array#partition, but where partition only does
> a true/false check, the resulting array should be partitioned by the
> return value of a block so that:
>
> a = ['a','bc','def','g','hi','jkl','m']
> group(a) {|i| i.size} #=> [["a", "g", "m"], ["bc", "hi"], ["def", "jkl"]]
>
>
> My best effort so far is this:
>
> def group array, &block
>   h = {}
>   array.each do |e|
>     (h[yield(e)]||=[])<<e
>   end
>   h.to_a.map {|e| e[1] }
> end


def group a
a.inject({}){|h,v|(h[yield(v)]||=[])<<v;h}.values
end

slightly more compact, but not very original.  I copied  from you and ara.
Doesn't look too noice either.

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