From: Jason Mayer <slamboy@...>
Date: 2007-01-17T21:42:32+09:00
Subject: Re: How does Array.map work for 2D arrays?

------=_Part_135381_31841364.1169037749858
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

On 1/14/07, Robert Klemme <shortcutter@googlemail.com> wrote:
>
> On 14.01.2007 12:49, karthik wrote:
> I guess the latter.  What you see is basically the effect of a
> combination of features: You're actually not dealing with a 2D Array but
> with an Array that contains Arrays, or more generally, an Enumerable
> that contains Enumerables.  A true 2D Array would make sure that every
> row has the same number of elements and similarly for columns, that's
> why it's not a 2D Array.  The other aspect is how yield and assignments
> work.  There is some automatic, err, how would you call that, unrolling?
>
> So, an Array is automatically assigned element wise you do not need to
> explicitly provide the splat operator:
>
> irb(main):007:0> a,b=*[1,2]
> => [1, 2]
> irb(main):008:0> a
> => 1
> irb(main):009:0> b
> => 2
>
> You can do a lot more fancy stuff with this as Ruby actually does
> pattern matching:
>
> irb(main):001:0> a,b,c=1,[2,3]
> => [1, [2, 3]]
> irb(main):002:0> a
> => 1
> irb(main):003:0> b
> => [2, 3]
> irb(main):004:0> c
> => nil
> irb(main):005:0> a,(b,c)=1,[2,3]
> => [1, [2, 3]]
> irb(main):006:0> a
> => 1
> irb(main):007:0> b
> => 2
> irb(main):008:0> c
> => 3
>
> This is often useful when using #inject on a Hash:
>
> $ irb
> irb(main):001:0> h={}
> => {}
> irb(main):002:0> 10.times { i=rand(10); h[i]=10-i}
> => 10
> irb(main):003:0> h
> => {0=>10, 6=>4, 7=>3, 2=>8, 8=>2, 3=>7, 9=>1, 4=>6}
> irb(main):004:0> h.size
> => 8
> irb(main):005:0> h.inject(0) {|sum,(key,val)| sum + key + val}
> => 80
>
> This is of course a silly example.  I chose these values in order to
> make checking what's going on easier (i.e. summing all keys and values
> equals h.size * 10).
>
> Kind regards
>
>        robert


Just wanted to throw in another set of thanks(late, I know); that response
very clearly answered a question I had regarding map.

------=_Part_135381_31841364.1169037749858--