From: Tony Arcieri <tony@...>
Date: 2009-06-15T04:35:28+09:00
Subject: Re: each by arity

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On Sun, Jun 14, 2009 at 1:29 PM, Trans <transfire@gmail.com> wrote:

> I don't see how the former is ever of any use, but the later certainly
> is. am i missing something obvious?
>

The main use I've seen is for iterating hashes, e.g.:

>> {:a => 1, :b => 2, :c => 3}.map { |k, v| "#{k}=#{v}" }.join(",")
=> "b=2,c=3,a=1"

Of course you could always massign against an incoming array, so this case
is also covered by:

>> {:a => 1, :b => 2, :c => 3}.map { |(k, v)| "#{k}=#{v}" }.join(",")
=> "b=2,c=3,a=1"

The massign approach is nice with methods where you want to explode an array
as arguments alongside other arguments:

>> {:a => 1, :b => 2, :c => 3}.inject(0) { |n, (k, v)| n + v }
=> 6

Personally I'm not a fan of this mode of arity handling and think massign
and splats cover all the cases where it's useful.

-- 
Tony Arcieri
medioh.com

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