[ruby-core:42626] [ruby-trunk - Feature #1125] [*x] (array consisting only of a splat) does not necessarily return a new array

Issue #1125 has been updated by Yusuke Endoh.

Assignee changed from Yusuke Endoh to Nobuyoshi Nakada

Hello,

2012/2/14 Nobuyoshi Nakada <[e-mail]>:
> Isn't the flag of splatarray for this purpose?

I don't know.  Please go ahead.  You have control!

-- 
Yusuke Endoh <[e-mail]>
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Feature #1125: [*x] (array consisting only of a splat) does not necessarily return a new array
https://bugs.ruby-lang.org/issues/1125

Author: Daniel Luz
Status: Assigned
Priority: Normal
Assignee: Nobuyoshi Nakada
Category: 
Target version: 2.0.0
ruby -v: ruby 1.8.7 (2008-08-11 patchlevel 72) [x86_64-linux]


=begin
 For [*x], these are basically the possible outcomes:
 
 1. if x is an Array, returns it unmodified.
 2. elsif x responds to to_ary (to_a on 1.9.1), invokes that method and returns its result unmodified.
 3. else, returns a new array with x as its only element.
 
 Cases #1 and #2 IMO violate the POLS, as I expected that an array literal would always return a new array. The practical consequence here is that I expected I'd be free to modify it without side effects. (For comparison, "#{x}" always returns a new string)
 
 Simple test case:
   x = [1, 2, 3]
   [*x] << 4
   p x # => [1, 2, 3, 4]
 
 
 Thus, I propose ensuring these two cases always return new arrays.
 One possible solution would be dup'ing the resulting array (I guess that'd have a rather low cost; the third case would result in an unnecessary dup, but at least it's just a single-item array). Another one would be to dumb down the interpreter, making it create a zero-length array and then concat the result of the splat to it.
=end



-- 
http://bugs.ruby-lang.org/