From: Robert Klemme <shortcutter@...>
Date: 2011-03-31T17:11:49+09:00
Subject: Re: How can I generate new variables?

On Thu, Mar 31, 2011 at 5:08 AM, Kyle X. <haebooty@yahoo.com> wrote:
> First off thank you for the reply, and as you can probably tell I am
> very novice at ruby ><. However I am running into a few issues with
> this.
>
>> Using arrays.  An array can contain anything--including other arrays:
>>
>>
>> require 'enumerator'  #not necessary in ruby 1.9
>>
>> master_arr = []
>> data = [1, 2, 3,  4, 5, 6,  7, 8]
>>
>> data.each_slice(3) do |triplet|
>>   master_arr << triplet
>> end
>>
>> p master_arr
>>
>> --output:--
>> [[1, 2, 3], [4, 5, 6], [7, 8]]
>
> I am writing this for SketchUP so I am using Ruby 1.8.6 and am having an
> issue with require 'enumerator', as it does not exist in their library
> as far as I can tell --- in turn the "each_slice" command does not
> function.

You can easily cook it yourself

module Enumerable
  def each_slice(n)
    a = []

    each do |x|
      a << x

      if a.size == n
        yield a
        a.clear
      end
    end

    yield a unless a.empty?
    self
  end
end

> I was wondering if you could help me understand this command better as
> well.  "data.each_slice(3) do |triplet|"  The "(3)" here means slice
> after 3 entries in data correct?

Correct.

>  The word triplet used, is this word
> required or could it be any word as long as it is consistent below i.e.
> :  do |x| master_arr << x?  Sorry for the basic question, but I just
> want to clarify.

Yes, it's the name of the block argument.  You can name it anyway you
like.  You should only avoid reusing a name used outside the block in
order to avoid confusion and incompatibility should the program be
executed on 1.9 at one day.

You can even use three names!

irb(main):041:0> Array.new(10) {|idx| idx}
=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
irb(main):042:0> Array.new(10) {|idx| idx}.each_slice(3)
{|first,second,third| p first}
0
3
6
9
=> nil

> The rest I think I have figured out, but still not 100% on the map
> function.

Enumerable#map sends all values through a conversion function and
collects them in a new Array:

irb(main):043:0> Array.new(10) {|idx| idx}.map {|x| x + 100}
=> [100, 101, 102, 103, 104, 105, 106, 107, 108, 109]

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/