From: Brian Candler <b.candler@...>
Date: 2009-07-14T23:48:56+09:00
Subject: Re: Elegant solution for inverting zip?

Gregory Brown wrote:
> On Tue, Jul 14, 2009 at 9:27 AM, Gregory 
> Brown<gregory.t.brown@gmail.com> wrote:
> 
> 
>> require "matrix"
>> b = Matrix[*a].column_vectors.map(&:to_a)
> 
> *facepalm*  Array#transpose is what I needed, I can't believe I forgot
> that.  Thanks goes to David Black via IM.

That's funny - I was just trying to do more or less the same thing the 
other day. Given an array of [k,v] pairs, I needed to turn it into an 
array of k's and an array of v's.

I searched for a built-in method to do this, couldn't find it, so went 
for the obvious solution:

    ks = src.collect { |k,v| k }
    vs = src.collect { |k,v| v }

But now I know a better way:

    ks, vs = src.transpose

Thanks for sharing!
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