From: "Matthias Wächter" <matthias@...>
Date: 2011-11-28T23:49:40+09:00
Subject: Re: Is high-speed sorting impossible with Ruby?

On 28.11.2011 15:17, Gaurav C. wrote:
> What's the difference between Array.new(1e6+1) {|n| ""} and
> Array.new(1e6+1, "")?

The first one creates one array with 1e6+1 _different_ empty strings. 
The second one results in an array that holds 1e6+1 references to the 
_same_ empty string.

Note that the following code variants both work as expected:

> a = Array.new(1e6+1) {""}
>
> …
>   a[l.to_i] << l
> …

> a = Array.new(1e6+1, "")
>
> …
>   a[l.to_i] += l
> …

but not this one:

> a = Array.new(1e6+1, "")
>
> …
>   a[l.to_i] << l
> …

String#+ creates a new string object while String#<< modifies the 
current string object.

– Matthias