From: dblack@...
Date: 2006-11-21T13:46:15+09:00
Subject: Re: array question

Hi --

On Tue, 21 Nov 2006, Li Chen wrote:

> Hi all,
>
> I want to build a new array from an old one with every element being
> duplicated except the first and last element. And here are my codes. I
> wonder if this is a real Ruby way to do it.

Here's one way, along with some tests:

require 'test/unit'

class ChangeArrayTest < Test::Unit::TestCase

   def change_array(a)
     [*1...a.size-1].reverse.each {|i| a.insert(i,a[i]) }
     a
   end

   def test_empty_array
     assert_equal([], change_array([]))
   end

   def test_one_element_array
     assert_equal([1], change_array([1]))
   end

   def test_two_element_array
     assert_equal([1,2], change_array([1,2]))
   end

   def test_three_element_array
     assert_equal([1,2,2,3], change_array([1,2,3]))
   end

   def test_ten_element_array
     assert_equal([1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10],
     change_array([1,2,3,4,5,6,7,8,9,10]))
   end
end


David

-- 
                   David A. Black | dblack@rubypal.com
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org