From: Robert Klemme <shortcutter@...>
Date: 2009-12-02T01:32:23+09:00
Subject: Re: Splat array with 1 value in Ruby 1.9 vs Ruby 1.8

2009/12/1 Raul Parolari <raulparolari@gmail.com>:
> Rick Denatale wrote:
>> On Tue, Dec 1, 2009 at 12:53 AM, Raul Parolari <raulparolari@gmail.com>
>> wrote:
>>>
>>> Of course, this can be handled by generating code that checks the array
>>> size. But I am curious on this behavior of splat when the array contains
>>> one element (I read about the features of splat in 1.9, but they seem to
>>> have nothing to do with this). Does anyone know if it is a bug or
>>> intentional?
>>
>>
>> Not sure exactly what you mean by generating the code, but could you use
>>
>> var1 = val1
>> and
>> var1, var2, varn = val1, val2, valn
>>
>>
>>
>> --
>> Rick DeNatale
>>
>> Blog: http://talklikeaduck.denhaven2.com/
>> Twitter: http://twitter.com/RickDeNatale
>
> As I said at the beginning of the post, the code is unpacking binary
> strings, which generates an array (else of course I would have not added
> the array, just for the fun of having to remove it). For example:
>
>   x, y = "\x23\x00\x61".unpack('Cn')  # => [35, 97]; so: x = 35; y = 97
>
> Now, when there is just one variable to extract, we get (as expected):
>
>   z="\x00\x61".unpack('n')   # z = [97]
>
> To get the scalar values in both cases, in 1.8.7 a splat operator in
> front of the right value expression (placed by the code generator) does
> the job; in 1.9.1, it does not. The solution is simple, but I was not
> asking for "a solution".
>
> In other words, I was just pointing out this difference of behavior:
>
>  a = *[ 3 ]   # =>  a =3        with Ruby 1.8.7
>
>  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


-- 
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