From: Brad Phelan <phelan@...>
Date: 2007-05-31T02:55:08+09:00
Subject: Re: Enumerable#serially - those nifty functions w/o memory footprint

Brad Phelan wrote:
> Brian Candler wrote:
>> On Wed, May 30, 2007 at 10:46:33PM +0900, SonOfLilit wrote:
>>> Sorry, found a bug, I'll need to make it into this:
>>>
>>> module Enumerable
>>>  def serially(&b)
>>>    a = []
>>>    self.each{|x| t = ([x].instance_eval(&b); a << b[0] unless b.empty?}
>>>    # notice, relevance to "it" discussion that's currently going on, 
>>> just    btw
>>>  end
>>> end
>>
>> Somehow I don't think you tested this :-)
>>
>> * You have mismatched parentheses
>> * You assign to t, but never use the value
>> * you call b twice, once with no arguments, and once with 0 as an 
>> argument
>> * b is a block, but you call #empty? on it
>>
>> Can you give an example of how this is supposed to be used?
>>
>> Brian.
>>
> 
> I think I get his point. I wrote a little lib to try out my 
> interpretation of what he is trying to do.
> 
> 
> a = (1..20)
> 
> b = a.serially do
>     select do |x|
>         if x > 10
>             true
>         else
>             false
>         end
>     end
>     collect do |x|
>         "0x" + x.to_s
>     end
>     select do |x|
>         if x == "0x15"
>             false
>         else
>             true
>         end
>     end
> end
> 
> puts b
> 
> 
> 
> # generates
> 
> 0x11
> 0x12
> 0x13
> 0x14
> 0x16
> 0x17
> 0x18
> 0x19
> 0x20
> 
> The lib is at
> 
> http://xtargets.com/snippets/posts/show/69
> 
> -- 
> Brad Phelan
> http://xtargets.com/snippets
> 

A quick profile with ruby-prof find the above technique about 10 times 
slower in 50000 elements than for the traditional method.

--
Brad Phelan
http://xtargets.com