From: Robert Klemme <shortcutter@...>
Date: 2011-09-05T16:12:51+09:00
Subject: Re: loops problem

On Sun, Sep 4, 2011 at 5:21 PM, Josh Cheek <josh.cheek@gmail.com> wrote:
> On Sun, Sep 4, 2011 at 9:45 AM, jack jones <shehio_22@hotmail.com> wrote:
>
>> I've read about the method which inserts some element in a certain place
>> ..
>> what I wanted to do is to shift all the elements to the back .. not
>> inserting which will require rather complicated operation like deleting
>> the element after shifting it .... I really don't understand the line
>> you wrote, thank you :)

> Insert nil. There are lots of options for docs.
> rdoc.info: http://rdoc.info/stdlib/core/1.9.2/Array#insert-instance_method
> ruby-doc.org: http://ruby-doc.org/core/classes/Array.html#M000230
>
> And you can't have an array with a "gap" in it. ie what is returned if you
> access that index after you've shifted the elements? The obvious answer is
> nil, so just insert nil:
>
> array = (0..10).to_a
> counter = 5
> array.insert counter, nil
> array # => [0, 1, 2, 3, 4, nil, 5, 6, 7, 8, 9, 10]

And if the length should stay the same an additional array.pop will
remove the last element.

Btw, for inserting multiple elements one can do:

irb(main):004:0> a=10.times.to_a
=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
irb(main):005:0> a[5,0] = Array.new 3
=> [nil, nil, nil]
irb(main):006:0> a.pop 3
=> [7, 8, 9]
irb(main):007:0> a
=> [0, 1, 2, 3, 4, nil, nil, nil, 5, 6]
irb(main):008:0> a.length
=> 10

Kind regards

robert

-- 
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