From: Rob Biedenharn <Rob@...>
Date: 2007-06-29T07:24:46+09:00
Subject: Re: Array.join for nested arrays

On Jun 28, 2007, at 4:29 PM, Robert Dober wrote:
> On 6/28/07, fu <freeunli@yahoo.com> wrote:
>> Martin, thanks! Should the behavior of "join" be like this or the  
>> docs
>> are wrong?
>>
> Very surprised about this behavior, IMHO it is wrong, at least it is
> inconsistent :
>
> irb(main):007:0>  a=[1,[2,[3,4],5],6]
> => [1, [2, [3, 4], 5], 6]
> irb(main):008:0>  a.join(",")
> => "1,2,3,4,5,6"
> irb(main):009:0>  b=[1,{2=>42},{3=>[4,5]}]
> => [1, {2=>42}, {3=>[4, 5]}]
> irb(main):010:0>  b.join(",")
> => "1,242,345"
>
> Robert
> -- 
> I always knew that one day Smalltalk would replace Java.
> I just didn't know it would be called Ruby
> -- Kent Back

Have you look at how Array#to_s is described as returning Array#join  
(the only difference being that to_s doesn't accept an argument and  
the default value of the separator is $,)?

irb(main):001:0> a = [1,[2,[3,4],5],6]
=> [1, [2, [3, 4], 5], 6]
irb(main):002:0> a.to_s
=> "123456"
irb(main):003:0> a.join(',')
=> "1,2,3,4,5,6"
irb(main):004:0> $, = '-'
=> "-"
irb(main):005:0> a.to_s
=> "1-2-3-4-5-6"
irb(main):006:0> a.join
=> "1-2-3-4-5-6"
irb(main):007:0> a.join(',')
=> "1,2,3,4,5,6"

Hmm, what about that one with the hash for an element?  (Remember, $,  
is still redefined to '-')

irb(main):008:0> b=[1,{2=>42},{3=>[4,5]}]
=> [1, {2=>42}, {3=>[4, 5]}]
irb(main):009:0> b.to_s
=> "1-2-42-3-4-5"
irb(main):010:0> b.join(',')
=> "1,2-42,3-4-5"

Hash#to_s first converts to an array of [key,value] pairs and then  
converts that to a string using Array#join with the default separator.

It seems that the use of "default" here, means the $, from Array#join 
(separator=$,), not the argument given to b.join

OK, one more:

irb(main):011:0> b.last[4]=6
=> 6
irb(main):012:0> b
=> [1, {2=>42}, {3=>[4, 5], 4=>6}]
irb(main):013:0> b.join(',')
=> "1,2-42,3-4-5-4-6"

Possibly unexpected, but I don't see it as inconsistent.

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com