From: "David A. Black" <dblack@...>
Date: 2010-06-07T22:08:39+09:00
Subject: Re: inject method of Array class

Hi --

On Mon, 7 Jun 2010, Robert Klemme wrote:

> 2010/6/7 David A. Black <dblack@rubypal.com>:
>
>> On Mon, 7 Jun 2010, Rein Henrichs wrote:
>>
>>> On 2010-06-06 17:55:58 -0700, David A. Black said:
>
>>> I suspect that the majority are overwritten for performance reasons,
>>> although some of them surprise me as well.
>>>
>>> A linked list, for instance, would have a constant time #count because
>>> that state is kept on the list object and doesn't require an O(n)
>>> enumeration of the members.
>>
>> I think it's a mixture of performance reasons and things like what it
>> should return if there's no block (like Enumerable#map always
>> returning an array vs. Array#map returning its receiver). Array is
>> definitely the one that has the most overrides, with Hash coming in
>> second at 6 and IO having none.
>
> David, I guess you meant to write "... vs. Array#map! returning its
> receiver"?  Note the exclamation mark.  Array#map returns a new Array
> on every invocation.

I really meant to say a copy of its receiver -- I was looking at this:

     if (!rb_block_given_p()) {
         return rb_ary_new4(RARRAY(ary)->len, RARRAY(ary)->ptr);
     }

from array.c.


David

-- 
David A. Black, Senior Developer, Cyrus Innovation Inc.

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