From: Jason Foreman <threeve.org@...>
Date: 2005-07-29T01:15:46+09:00
Subject: Re: Joining an Array of Arrays

On 7/28/05, Jesse Merriman <jessemerriman@warpmail.net> wrote:
> Hi,
> 
> I tried joining an Array of Arrays, and it seems the Array
> is being flattened first or something.
> 
> ri Array#join tells me:
>   Returns a string created by converting each element of the array to
>   a string, separated by _sep_.
> 
> Its the part about each element getting converted to a string that
> seems wrong:
> 
> > x = [[1, 2], [3, 4]]
> > print x[0].to_s, ' ', x[1].to_s #=> "12 34"
> > x.join(' ')                     #=> "1 2 3 4"
> 
> I expected join to produce "12 34"; why doesn't it?
> 

This boggled me for a while, had to actually look at the source for Array#join.

It does not simply call to_s when the sub-element is an array. 
Essentially, it does a recursive call to join for elements that are
themselves arrays, passing in the original separator (' ' in this
case).


Jason