From: "David A. Black" <dblack@...>
Date: 2003-12-05T23:22:27+09:00
Subject: Batch key/value setting in a hash (was Re: Dumb question to which I ought to know the answer by now)

Hi --

[Changed the subject to something more informative :-) ]

On Fri, 5 Dec 2003, Austin Ziegler wrote:

> On Fri, 5 Dec 2003 13:57:04 +0900, Mark J. Reed wrote:
> > On Fri, Dec 05, 2003 at 01:45:36PM +0900, Austin Ziegler wrote:
> >> hash = { :a => 3, :b => 2, :c => 1, :d => 0}
> >> hash.update({ :a => 1, :b => 2, :c => 3 })
> > I know that, but in this case I have the keys and values in two arrays
> > and want to match them up by position.  In other words, I want to do this:
> 
> > keys.each_with_index do
> > |k, i|
> > hash[k] = values[i]
> > end
> 
> > The equivalent of Perl @hash{@keys} = @values.
> 
> Unfortunately, that won't work in Ruby because arrays can be keys, whereas
> in Perl, hash keys can only be scalars.
> 
> What you can do is:
> 
> hash = nil; keys.zip(value) { |k, v| (hash ||= {})[k] = v }

Or, using the handy flattenx extension from RAA:

  irb(main):001:0> require 'flattenx'
  => true
  irb(main):002:0> a = [ [1],2,3 ]; b = [ 4, [5,6], 7]
  => [4, [5, 6], 7]
  irb(main):003:0> Hash[*a.zip(b).flatten_by(1)]
  => {[1]=>4, 2=>[5, 6], 3=>7}

(to avoid over-flattening)


David

-- 
David A. Black
dblack@wobblini.net