Array index confusion

Ruby
1

I cannot find an answer to this, and perhaps the answer is that “it is
what it is…” But perhaps someone can explain this for me.

If I have an array, thus:
a = [1, 2, 3, 4]
there are four elements in the array. The indexes are 0…3.

a[4,0] returns []

a[5,0], however, returns nil

Both of these are outside the scope of the array, aren’t they? I would
think they would return the same thing, either nil or the empty array.

Any help? Thanks!

John

2

Am 20.06.2012 23:27, schrieb John R.:

Both of these are outside the scope of the array, aren’t they? I would
think they would return the same thing, either nil or the empty array.

Maybe this helps:

http://stackoverflow.com/questions/3568222/array-slicing-in-ruby-looking-for-explanation-for-illogical-behaviour-taken-fr

Regards,
Marcus

3

See this post for an explanation:
http://www.ruby-forum.com/topic/1393096#990065

– Matma R.

4

Am 20.06.2012 23:38, schrieb Bartosz Dziewoński:

See this post for an explanation: String/array slices - Ruby - Ruby-Forum

This behavior definitely should be documented in the Array class.

5

On 06/20/2012 11:07 PM, [email protected] wrote:

Am 20.06.2012 23:38, schrieb Bartosz Dziewoński:

See this post for an explanation:
String/array slices - Ruby - Ruby-Forum

This behavior definitely should be documented in the Array class.

Good idea. Here’s how:

-Justin

6

On 06/21/2012 11:13 PM, [email protected] wrote:

Is this obsolete:
http://www.ruby-doc.org/documentation-guidelines.html ?

Regards,
Marcus

That site looks more specific to ruby-doc.org (e.g., using “stdlib-doc”
to generate docs, instead of rdoc). I don’t know if following those
instructions will work or not. The instructions in the link I sent will.

-Justin

7

Am 22.06.2012 00:56, schrieb Justin C.:

On 06/20/2012 11:07 PM, [email protected] wrote:

…

This behavior definitely should be documented in the Array class.

Good idea. Here’s how:

Ruby Documentation Project

Is this obsolete:
http://www.ruby-doc.org/documentation-guidelines.html ?

Regards,
Marcus

8

It’s always humbling when you realize other people have thought through
complicated stuff before you.

Dave

9

A late update: I submitted a patch for the documentation,
see https://bugs.ruby-lang.org/issues/6680