From: Rein Henrichs <reinh@...>
Date: 2010-06-07T10:25:05+09:00
Subject: Re: inject method of Array class

On 2010-06-06 17:55:58 -0700, David A. Black said:

> Hi --
> 
> On Mon, 7 Jun 2010, Rein Henrichs wrote:
> 
>> In addition to the previously mentioned difference between #methods and
>> #instance_methods, #inject is actually a method on the Enumerable module,
>> which is mixed into Array (and other classes that have #each). The Enumerable
>> module is full of methods that can be used on "things that can enumerate
>> themselves", like Arrays, Hashes and Sets.
> 
> Although a surprising (to me) number of Enumerable's instance methods
> are overridden in Array:
> 
> irb(main):008:0> (Array.instance_methods(false) &
> Enumerable.instance_methods).sort
> => ["collect", "count", "cycle", "drop", "drop_while", "find_index",
> "first", "include?", "map", "reject", "reverse_each", "select",
> "sort", "take", "take_while", "to_a", "zip"]
> 
> (That's 1.8.7 but the list is the same in 1.9.1.)
> 
> 
> David

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.

-- 
Rein Henrichs
http://puppetlabs.com
http://reinh.com