From: Ken Bloom <kbloom@...>
Date: 2007-12-31T12:39:58+09:00
Subject: Re: Using "sort!" in a C extension (1.9 problem)

On Sat, 29 Dec 2007 19:30:31 -0500, Andre Nathan wrote:

> On Sun, 2007-12-30 at 08:06 +0900, Andre Nathan wrote:
>> On Sun, 2007-12-30 at 07:34 +0900, Siep Korteling wrote:
>> > Like this?
>> > a=[[2],[1,2,3],[1],[1,2]]
>> > p a.sort_by{|ar|ar.length}
>> 
>> Yes but in a C extension. The code I have is not working with 1.9.
> 
> Well not exactly. sort_by works but I'd prefer to use sort! with a
> block, as it does the sorting in-place.
> 
> In 1.9, if I inspect "ary" below, I only see the current array element.
> In 1.8, it is an array of the two elements which are being compared.
> 
> static VALUE
> sort_i(VALUE ary)
> {
>     long v1 = FIX2LONG(RARRAY_PTR(ary)[0]); long v2 =
>     FIX2LONG(RARRAY_PTR(ary)[1]); return LONG2FIX(v1 - v2);
> }
> 
> Andre

This appears to be the result of a ruby 1.9 semantic change for block 
arguments.


(from eigenclass.org's summary)
> News semantics for block arguments
> 
> |v| now works like the former |v,|:
> 
> [RUBY_VERSION, RUBY_RELEASE_DATE] # => ["1.8.5", "2006-08-25"]
> def m; yield 1, 2; end
> m{|v| v}                                          # => [1, 2] # !> 
> multiple values for a block parameter (2 for 1)
> 
> vs.
> 
> [RUBY_VERSION, RUBY_RELEASE_DATE] # => ["1.9.0", "2007-08-03"]
> def m; yield 1, 2; end
> m{|v| v}                                          # => 1

So sort_i needs to be revised to take two parameters, as follows:

static VALUE
sort_i(VALUE first, VALUE second)
{
    long v1 = FIX2LONG(first);
    long v2 = FIX2LONG(second);
    return LONG2FIX(v1 - v2);
}

(Note that I have not tested this, and I have not programmed a C 
extension ever without the help of SWIG.)

--Ken

-- 
Ken (Chanoch) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/