[#390749] Why are there so many similar/identical methods in core classes — Kassym Dorsel <k.dorsel@...>

Let's look at the Array class and start with method aliases.

14 messages 2011/12/02

[#390755] Inverse Operation of Module#include — Su Zhang <su.comp.lang.ruby@...>

Hi list,

21 messages 2011/12/02
[#390759] Re: Inverse Operation of Module#include — Ryan Davis <ryand-ruby@...> 2011/12/02

[#390764] Re: Inverse Operation of Module#include — Isaac Sanders <isaacbfsanders@...> 2011/12/02

I would suggest an Adapter pattern use here. IF there is something that has

[#390795] Is there a better way to check this array? — Wayne Brissette <wbrisett@...>

I have an array which contains items that need to be renamed. Unfortunately the way things are changed are based on a comparison of if something else exists. For example in this simple array:

9 messages 2011/12/03

[#390876] black magical hash element vivification — Chad Perrin <code@...>

Ruby (1.9.3p0 to be precise, installed with RVM) is not behaving as I

12 messages 2011/12/05

[#390918] WEB SURVEY about Ruby Community — Intransition <transfire@...>

Did any one else get this survey request?

14 messages 2011/12/07

[#390972] Which is the best online document conversion site? — "Maria M." <mariamoore952@...>

Can anyone tell me that which is the best online document conversion

7 messages 2011/12/08

[#390976] Confusing results from string multiplication — Rob Marshall <robmarshall@...>

Hi,

19 messages 2011/12/08

[#391019] How can I do h["foo"] += "bar" if h["foo"] does not exist? — "Andrew S." <andrewinfosec@...>

Hi there,

13 messages 2011/12/09

[#391027] reading from file without end-of-lines — Janko Muzykant <umrzykus@...>

hi,

20 messages 2011/12/09
[#391028] Re: reading from file without end-of-lines — Gavin Sinclair <gsinclair@...> 2011/12/09

> i'm trying to read a few text values from single file:

[#391031] Re: reading from file without end-of-lines — Robert Klemme <shortcutter@...> 2011/12/09

On Fri, Dec 9, 2011 at 9:58 AM, Gavin Sinclair <gsinclair@gmail.com> wrote:

[#391042] Re: reading from file without end-of-lines — Gavin Sinclair <gsinclair@...> 2011/12/09

On Fri, Dec 9, 2011 at 8:18 PM, Robert Klemme

[#391135] I need advice on what to do next. — Nathan Kossaeth <system_freak_2004@...>

I am new to programming. I read the ebook "Learn to Program" by Chris

23 messages 2011/12/12

[#391216] perf optimization using profile results — Chuck Remes <cremes.devlist@...>

I need some help with optimizing a set of libraries that I use. They are ffi-rzmq, zmqmachine and rzmq_brokers (all up on github).

13 messages 2011/12/13
[#391218] Re: perf optimization using profile results — Chuck Remes <cremes.devlist@...> 2011/12/13

On Dec 13, 2011, at 9:57 AM, Chuck Remes wrote:

[#391234] Re: perf optimization using profile results — Charles Oliver Nutter <headius@...> 2011/12/14

A couple quick observations.

[#391238] Re: perf optimization using profile results — Chuck Remes <cremes.devlist@...> 2011/12/14

On Dec 13, 2011, at 7:03 PM, Charles Oliver Nutter wrote:

[#391324] ruby 1.9 threading performance goes non-linear — Joel VanderWerf <joelvanderwerf@...>

12 messages 2011/12/16
[#391325] Re: ruby 1.9 threading performance goes non-linear — Eric Wong <normalperson@...> 2011/12/16

Joel VanderWerf <joelvanderwerf@gmail.com> wrote:

[#391420] Accessing class instance variables from an instance? — "Shareef J." <shareef@...>

Hi there,

26 messages 2011/12/20
[#391454] Re: Accessing class instance variables from an instance? — Khat Harr <myphatproxy@...> 2011/12/21

Actually, now that I'm thinking about it the existing behavior sort of

[#391456] Re: Accessing class instance variables from an instance? — Josh Cheek <josh.cheek@...> 2011/12/21

On Tue, Dec 20, 2011 at 9:42 PM, Khat Harr <myphatproxy@hotmail.com> wrote:

[#391545] Kernel#exit raises an exception? — Khat Harr <myphatproxy@...>

While I was working on embedding an interpreter I wrote a function to

13 messages 2011/12/24

[#391618] rvmsh: An easy installer for RVM — Bryan Dunsmore <dunsmoreb@...>

I have recently begun work on a project called [rvmsh]

12 messages 2011/12/29

[#391783] Mailspam — Gunther Diemant <g.diemant@...>

Is there a way to stop this mailspam of Luca (Mail)?

12 messages 2011/12/29

[#391790] What’s the standard way of implementing #hash for value objects in Ruby? — Nikolai Weibull <now@...>

Hi!

23 messages 2011/12/29
[#391792] Re: What’s the standard way of implementing #hash for value objects in Ruby? — Gunther Diemant <g.diemant@...> 2011/12/29

I think you can't access instance variables from a class method, so

[#391793] Re: What’s the standard way of implementing #hash for value objects in Ruby? — Nikolai Weibull <now@...> 2011/12/29

On Thu, Dec 29, 2011 at 15:52, Gunther Diemant <g.diemant@gmx.net> wrote:

[#391811] Re: What’s the standard way of implementing #hash for value objects in Ruby? — Robert Klemme <shortcutter@...> 2011/12/29

On Thu, Dec 29, 2011 at 4:06 PM, Nikolai Weibull <now@bitwi.se> wrote:

[#391812] Re: What’s the standard way of implementing #hash for value objects in Ruby? — Nikolai Weibull <now@...> 2011/12/29

On Fri, Dec 30, 2011 at 00:26, Robert Klemme <shortcutter@googlemail.com> wrote:

[#391816] Re: What’s the standard way of implementing #hash for value objects in Ruby? — Josh Cheek <josh.cheek@...> 2011/12/30

On Thu, Dec 29, 2011 at 5:47 PM, Nikolai Weibull <now@bitwi.se> wrote:

[#391833] Re: What’s the standard way of implementing #hash for value objects in Ruby? — Robert Klemme <shortcutter@...> 2011/12/30

On Fri, Dec 30, 2011 at 12:47 AM, Nikolai Weibull <now@bitwi.se> wrote:

Re: Hash access

From: Gary Wright <gwtmp01@...>
Date: 2011-12-30 23:05:06 UTC
List: ruby-talk #391848

On Dec 30, 2011, at 4:59 PM, Ryan Davis wrote:
> The other confusion for you is insisting it is eql? instead of ==. Yong Li nailed the description of how it works. Please read it again. It is as close to perfect as we're going to get.
> 
> Also, as pointed out on the other hash thread... There _needs_ to be a 1:1 correlation between the result of #== and the result of #hash. You cannot simply use the "most relevant attribute". You _must_ use _all_ the attributes that you use against equality tests. Doing this is fundamental to ruby (and computer science) and must be thoroughly understood.

I think there are some errors and/or misleading statements in this
discussion.

First of all, the implementation of Hash depends on testing the
equality of two objects via #eql? and not via #==.  This is easy
to see by using 1 and 1.0 in a hash:

>> 1.hash #=> 3943323080027384908
>> (1.0).hash #=> -6757032739833615
>> 1 == 1.0 #=> true
>> 1.eql?(1.0) #=> false
>> h = {} #=> {}
>> h[1] = 'a' #=> "a"
>> h[1.0] = 'b' #=> "b"
>> h #=> {1=>"a", 1.0=>"b"}

If #== was being used by Hash, the hash at the end of that sequence
would only have one entry with a key of 1.0.

I don't think it is correct to call the relationship between eql?
and == to be one-to-one.

(a == b) implies (a.hash == b.hash)

but the reverse is not true.

(a.hash == b.hash) does not imply (a == b)

If two objects have the same hash, they may or may not be equal.
If they aren't equal, you just have a hash collision that has to
be disambiguated by doing a full equality test via eql?.

Finally, there is no hard requirement that a hash implementation
'must use all the attributes' used for the equality test. If there
is a subset of attributes that are generally different for non-equal
objects then the hash function will be more performant if it only
uses the subset of attributes.

The important point is that you don't want your hash function to
create too many collisions where non-equal objects have the same
hash function.

For example:

   def hash; 1; end

will 'work' but will cause performance problems when those objects
are stored in a Hash:

require 'benchmark'

class A; end
class B; def hash; 1; end; end

n = 10000;

Benchmark.bm(20) do |x|
  x.report('Object#hash') { h = {}; n.times { |i| h[A.new] = i }; } 
  x.report('1')           { h = {}; n.times { |i| h[B.new] = i }; } 
end

                           user     system      total        real
Object#hash            0.010000   0.000000   0.010000 (  0.008124)
1                      2.300000   0.000000   2.300000 (  2.311228)



Gary Wright


In This Thread