From: Love U Ruby <lists@...>
Date: 2013-02-24T18:45:28+09:00
Subject: Confusion with `nil` value being produced by IRB in case of Array#size manipulation.

enum[int] = obj → obj
enum[start, length] = obj → obj
enum[range] = obj → obj

During my reading and understandding with the above I tried something in
my IRB as below:

a = []
# => []
a.size
# => 0

Humm, understood. As no element I still added.

a[0]
# => nil
a[1]
# => nil

as the array size is `0`, while trying to access the a[1] getting no
exception - why so? that means index is there or what?
what logic does help IRB to  show such `nil` values?

a[1] = 5
# => 5
a
# => [nil, 5]

The above code what should I say - new value addition or substitution of
'nil'?

a.size
# => 2

Okay! so now the size is `2`.

Now in the below as the size is `2` thus a[3] is showing `nil`.
a[3]          <~~~~ point - I
# => nil
a.size
# => 2


Now I added `nil` in the same index intentionaly. And the size got
changed to `3`.

a[3] = nil
# => nil
a.size
# => 3
a[3]        <~~~~ point - II
# => nil

What is the difference between the output of a[3] in point- I and point
-II ?
Why does both `nil` value being treated differently as mentioned above?

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