From: Kedar Mhaswade <kedar.mhaswade@...>
Date: 2011-01-12T03:54:00+09:00
Subject: Re: Parallel Assignments and Elegance/Complexity Ratio.

Robert Klemme wrote in post #973945:
> On Tue, Jan 11, 2011 at 3:29 PM, Kedar Mhaswade
> <kedar.mhaswade@gmail.com> wrote:
>>
> 
https://docs1.google.com/document/d/1zpHvfO4be3UvjaxU7L5gEPXFMENcMmEz9qqIcecEzOg/edit?hl=en#
>>
>> Summary is, I should only spend time learning
>> - x, y, z = 1, 2, 3 (# => x=1, y=1, z=3), and
>> - x, y = y, x (# => swap x and y)
>>
>> I gather that this might be a matter of taste and style, but are other
>> variants used by community?
>
> Just today I used
>
>   def []=(*idx, val)
>     index_check(idx)
>     @data[idx] = val
>   end
>
> https://gist.github.com/772827
>
> See also thread "Nooby question : multidimensional arrays.".
>
> I find the pattern matching _very_ elegant.  This also comes in handy
> in situations like this:

Maybe I am not understanding it, but I thought that elegance is because 
of splat operator (which I am sure I like). My gripe is about various 
forms of parallel assignment and semantic/syntactic complexity because 
of that. Or are you saying that once you say you need splat operator, 
all this complexity is inevitable (of course, I can work around it by 
not using it, but then how do you all use it?)

-Kedar

>
> irb(main):001:0> a = Array.new(10) { [rand(10), rand(10)] }
> => [[2, 3], [7, 8], [4, 0], [4, 6], [5, 2], [9, 9], [4, 2], [8, 5],
> [2, 6], [5, 9]]
> irb(main):002:0> a.sort {|(a1,a2),(b1,b2)| x = a2 <=> b2; x == 0 ? a1
> <=> b1 : x}
> => [[4, 0], [4, 2], [5, 2], [2, 3], [8, 5], [2, 6], [4, 6], [7, 8],
> [5, 9], [9, 9]]
>
> Although in this particular case you could also use
>
> irb(main):004:0> a.sort_by {|arr| arr.reverse}
> => [[4, 0], [4, 2], [5, 2], [2, 3], [8, 5], [2, 6], [4, 6], [7, 8],
> [5, 9], [9, 9]]
> irb(main):005:0> a.sort_by {|x, y| [y, x]}
> => [[4, 0], [4, 2], [5, 2], [2, 3], [8, 5], [2, 6], [4, 6], [7, 8],
> [5, 9], [9, 9]]
>
> Generally I'd say I don't use it overly often but when I use it it is
> really handy.  With #inject it's also useful if you iterate through a
> collection of Arrays of known equal length:
>
> irb(main):006:0> a.inject(0) {|s,(x,y)| s + x + y}
> => 100
>
> Kind regards
>
> robert

-- 
Posted via http://www.ruby-forum.com/.