From: Ralph Shnelvar <ralphs@...32.com>
Date: 2009-11-15T18:19:51+09:00
Subject: Re: Array.assoc

Phrogz,


P> On Nov 14, 9:48�pm, Phrogz <phr...@mac.com> wrote:
>> On Nov 14, 9:31�pm, Ralph Shnelvar <ral...@dos32.com> wrote:
>>
>> > If I want to find the source to the Class Array ... specifically
>> > Array.assoc ... where would I look?
>>
>> Slim2:~ phrogz$ cd /usr/local/src/ruby-1.9.1-p243/
>> Slim2:ruby-1.9.1-p243 phrogz$ grep -E "define_method.+assoc" *.c
>> array.c: � �rb_define_method(rb_cArray, "assoc", rb_ary_assoc, 1);
>> array.c: � �rb_define_method(rb_cArray, "rassoc", rb_ary_rassoc, 1);
>> hash.c: � �rb_define_method(rb_cHash, "assoc", rb_hash_assoc, 1);
>> hash.c: � �rb_define_method(rb_cHash, "rassoc", rb_hash_rassoc, 1);
>>
>> So, look for the function named rb_cArray in the array.c file in the
>> ruby source code.

P> Bah, of course I meant rb_ary_assoc. Looking at your pasted text while
P> typing is bad. :p

P> As penance, here is the source code for that function:

P> VALUE
P> rb_ary_assoc(VALUE ary, VALUE key)
P> {
P>     long i;
P>     VALUE v;

P>     for (i = 0; i < RARRAY_LEN(ary); ++i) {
P>         v = rb_check_array_type(RARRAY_PTR(ary)[i]);
P>         if (!NIL_P(v) && RARRAY_LEN(v) > 0 &&
P>             rb_equal(RARRAY_PTR(v)[0], key))
P>             return v;
P>     }
P>     return Qnil;
P> }

Thank you very much.

(A) Is there a place online where I could have found this?  On my
Rails-installed system I have the source to ruby-1.8.6-p111 ... and
the source is slightly different.  ... Never mind ... I just found it
at http://ruby-doc.org/ruby-1.9/index.html by clicking on the title.
Grrr.

(B) Looking at this code is really fascinating to me.  It tells me, for
instance, that a Ruby array (at least in 1.9.1-p243) is really a C
array of pointers.  Nice!  I was concerned that it might translate
into some sort of array of array of pointers (sorta like how a FAT
table is implement to allocate files).

(C) Assume that ary is sorted by RARRAY_PTR(v)[0] so that one could do
a binary search instead of a linear search.  What user group would I
talk to to talk about adding arb_ary_sortedassoc?