From: Robert Klemme <shortcutter@...>
Date: 2009-12-02T02:25:06+09:00
Subject: Re: Splat array with 1 value in Ruby 1.9 vs Ruby 1.8

On 12/01/2009 05:56 PM, Raul Parolari wrote:
> Robert Klemme wrote:
>> 2009/12/1 Raul Parolari <raulparolari@gmail.com>:
>>>>
>>>
>>> ?a = *[ 3 ] ? # => a = [ 3 ] ? ?with Ruby 1.9.1
>>>
>>> I think that this is a bug in Ruby 1.9.
>> Regardless whether it is or is not a bug (I would not be so sure of
>> that), there is a way to fix it and handle it uniformly across Ruby
>> versions:
>>
>> 17:31:18 test$ allruby -e 'a = [123];b = *[456];c, = [789]; p a,b,c'
>> CYGWIN_NT-5.1 padrklemme1 1.5.25(0.156/4/2) 2008-06-12 19:34 i686 Cygwin
>> ========================================
>> ruby 1.8.7 (2008-08-11 patchlevel 72) [i386-cygwin]
>> [123]
>> 456
>> 789
>> ========================================
>> ruby 1.9.1p129 (2009-05-12 revision 23412) [i386-cygwin]
>> [123]
>> [456]
>> 789
>> ========================================
>> jruby 1.4.0 (ruby 1.8.7 patchlevel 174) (2009-11-02 69fbfa3) (Java
>> HotSpot(TM) Client VM 1.6.0_17) [x86-java]
>> [123]
>> 456
>> 789
>>
>> Look at variable "c".
>>
>> Kind regards
>>
>> robert
> 
> Indeed, this solves with grace the problem in the automation  (without 
> the easy but disturbing question on "how many elements the array has"):
> 
> a,b, = [ 3, 4 ]    # => a = 3; b = 4
> a,    = [ 3 ]         # => a  = 3
> 
> On the other matter ( a = *[ 3 ] ), I still think that it is a bug in 
> 1.9 (else I don't understand fully what a splat operator is, and I'd 
> like to know more).

I know there have been some things changed with regard to how the splat 
operator works, including more complex patterns:

robert@fussel:~$ ruby1.9 -e 'def f(a,*b,c)p a,b,c end;f(1, 2, 3, 4)'
1
[2, 3]
4

This did not work in 1.8:

robert@fussel:~$ ruby1.8 -e 'def f(a,*b,c)p a,b,c end;f(1, 2, 3, 4)'
-e:1: syntax error, unexpected tIDENTIFIER, expecting tAMPER or '&'
def f(a,*b,c)p a,b,c end;f(1, 2, 3, 4)
             ^
robert@fussel:~$

The changes may make it necessary that 1.9 behaves the way you observed. 
  That's why I said I am not sure whether it is actually a bug.

> But thanks a lot, Robert

You're welcome!

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/