From: Kristof Bastiaensen <kristof@...>
Date: 2004-06-18T20:58:33+09:00
Subject: Re: [RCR] More enumerator functionality

On Fri, 18 Jun 2004 01:54:19 +0900, Michael Neumann wrote:

> On Fri, Jun 18, 2004 at 12:03:44AM +0900, Kristof Bastiaensen wrote:
>> Hi everybody,
>> 
>> I have finally posted my RCR for more enumerator
>> functionality.
>> 
>> Find more about it here:
>> http://rcrchive.net/rcr/RCR/RCR262
> 
> Can you give some more examples, where and how enum_if could be useful?
> 
> Regards,
> 
>   Michael

Well, enum_if is useful in at least two cases (as I wrote in
the analysis).  It could be useful as a replacement for 
Enumerable#select that may be more efficient in some cases,
(when dealing with a large amount of data). 
For example:
  large_dataset.enum_if { |d| sometest(d) }.collect do |d|
    <data manipulation>
  end

It could also be useful to have a specialized enumerator
that will reflect any changes made to the original object:

data = ["a", 6, 9, "foo", -19, "fuga", -19, "bach"]
ints = data.enum_if { |i| i.is_a? Numeric }
ints.to_a
=>  [6, 9, -19, -19]

data += ["Bear", 20, 3]
ints.to_a
=> [6, 9, -19, -19, 20, 3]

(I have added these examples to the RCR)

Cheers,
Kristof