Ruby&#39;s `sort` doesn&#39;t sort in-place. (Do you have a Python background, perhaps?)

Ruby has `sort!` for in-place sorting, but there&#39;s no in-place variant for `sort_by` in Ruby 1.8. In practice, you can do:

    sorted = sort_me.sort_by { |k| k[&quot;value&quot;] }
    puts sorted

As of Ruby 1.9+, `.sort_by!` is available for in-place sorting:

    sort_me.sort_by! { |k| k[&quot;value&quot;]}

As per @shteef but implemented with the `sort!` variant as suggested:

    sort_me.sort! { |x, y| x[&quot;value&quot;] &lt;=&gt; y[&quot;value&quot;] }

Although Ruby doesn&#39;t have a `sort_by` in-place variant, you can do:

    sort_me = sort_me.sort_by { |k| k[&quot;value&quot;] }

---
`Array.sort_by!` was added in 1.9.2


You can use `sort_me.sort_by!{ |k| k[&quot;value&quot;]}`. This should work. 

I want to have a check in my javascript if the page loading up is on my local machine.

The reason why I want to do that is that when I developing I like to make sure that both my server side(C#) validation is working correctly. So I like to see both the client side and server sides errors to show up.


So while I am testing I have a flag in my jquery validate stuff that just always lets invalid data go through. This way I see the client side and server errors at one go.

However right now I have to manually go and change back and forth when going from development to production.



How to check with javascript if connection is local host?

I have a deleted file archive database that stores the ID of the file that was deleted,  I want the admin to be able to restore the file (as well as the same ID for linking files).  I do not want to take identity_insert off the entire table, as the increment by one works great.  In my insert to `TBL_Content` store procedure I have something like this
   

    set ANSI_NULLS ON
    set QUOTED_IDENTIFIER ON
    SET IDENTITY_INSERT tbl_content ON
    GO
    
    ALTER procedure [dbo].[spInsertDeletedIntoTBLContent]
    @ContentID int, 
    ...insert command...
    SET IDENTITY_INSERT tbl_content OFF

But I keep getting the same error:

&gt; Cannot insert explicit value for identity column in table
&gt; &#39;TBL_Content&#39; when IDENTITY_INSERT is set to OFF.

Any help?



IDENTITY_INSERT is set to OFF - How to turn it ON?

This Ruby code is not behaving as I would expect:

    # create an array of hashes
    sort_me = []
    sort_me.push({&quot;value&quot;=&gt;1, &quot;name&quot;=&gt;&quot;a&quot;})
    sort_me.push({&quot;value&quot;=&gt;3, &quot;name&quot;=&gt;&quot;c&quot;})
    sort_me.push({&quot;value&quot;=&gt;2, &quot;name&quot;=&gt;&quot;b&quot;})
    
    # sort
    sort_me.sort_by { |k| k[&quot;value&quot;]}

    # same order as above!
    puts sort_me

I&#39;m looking to sort the array of hashes by the key &quot;value&quot;, but they are printed unsorted.


How do I sort an array of hashes by a value in the hash?

This Ruby code is not behaving as I would expect:
<pre><code class="hljs language-ini"># create an array of hashes
sort_me = []
sort_me.push({"value"=>1, "name"=>"a"})
sort_me.push({"value"=>3, "name"=>"c"})
sort_me.push({"value"=>2, "name"=>"b"})

# sort
sort_me.sort_by { |k| k["value"]}

# same order as above!
puts sort_me
</code></pre>
I'm looking to sort the array of hashes by the key "value", but they are printed unsorted.

Is there a way to run command line commands through Ruby? I&#39;m trying to create a small little Ruby program that would dial out and receive/send through command line programs like &#39;screen&#39;, &#39;rcsz&#39;, etc.

It would be great if I could tie all this in with Ruby (MySQL backend, etc.)

Running command line commands within Ruby script

Having a string with the module and name of a class, like:

    &quot;Admin::MetaDatasController&quot;

how do I get the actual class?

The following code works if there&#39;s no module:

    Kernel.const_get(&quot;MetaDatasController&quot;)

but it breaks with the module:

    ruby-1.8.7-p174 &gt; Kernel.const_get(&quot;Admin::MetaDatasController&quot;)
    NameError: wrong constant name Admin::MetaDatasController
            from (irb):34:in `const_get&#39;
            from (irb):34
    ruby-1.8.7-p174 &gt; 

Get a class by name in Ruby?

I would like to know to how to do in Ruby what I can do with `system(&quot;clear&quot;)` in C.
I wrote a program like 

    puts &quot;amit&quot;
    system(&quot;clear&quot;)

I want the console to be cleared after executing this commnad, but it is not working.


How can I clear the terminal in Ruby?

Is there any major difference between `load` and `require` in the Ruby on Rails applications? Or do they both have the same functionality?


How does load differ from require in Ruby?

How to convert a ruby hash object to JSON? So I am trying this example below &amp; it doesn&#39;t work?

I was looking at the RubyDoc and obviously `Hash` object doesn&#39;t have a `to_json` method. But I am reading on blogs that Rails supports `active_record.to_json` and also supports `hash#to_json`. I can understand `ActiveRecord` is a Rails object, but `Hash` is not native to Rails, it&#39;s a pure Ruby object. So in Rails you can do a `hash.to_json`, but not in pure Ruby??


    car = {:make =&gt; &quot;bmw&quot;, :year =&gt; &quot;2003&quot;}
    car.to_json

How to convert a ruby hash object to JSON?

    int[] array1 = {1, 2, 3, 4, 5, 6, ,7, 8}; - working


    array1 = {1, 1, 1, 1, 2, 5, ,7, 8}; - NOT working

The first line is working, but second line is not working.

 How can I make the initialization from the second line in one single line of code? 

Java: How initialize an array in Java in one line?

I am trying to find the intersection values between multiple arrays.

for example

    code1 = [1,2,3]
    code2 = [2,3,4]
    code3 = [0,2,6]

So the result would be 2

I know in PHP you can do this with array_intersect

I wanted to be able to easily add additional array so I don&#39;t really want to use multiple loops

Any ideas ?

Thanks, Alex

rails - Finding intersections between multiple arrays

Previously answered questions here said that this was the fastest way:

    //nl is a NodeList
    var arr = Array.prototype.slice.call(nl);

In benchmarking on my browser I have found that it is more than 3 times slower than this:

    var arr = [];
    for(var i = 0, n; n = nl[i]; ++i) arr.push(n);

They both produce the same output, but I find it hard to believe that my second version is the fastest possible way, especially since people have said otherwise here.

Is this a quirk in my browser (Chromium 6)? Or is there a faster way?

EDIT: For anyone who cares, I settled on the following (which seems to be the fastest in every browser that I tested):

    //nl is a NodeList
    var l = []; // Will hold the array of Node&#39;s
    for(var i = 0, ll = nl.length; i != ll; l.push(nl[i++]));

EDIT2: I found an even faster way

    // nl is the nodelist
    var arr = [];
    for(var i = nl.length; i--; arr.unshift(nl[i]));


Fastest way to convert JavaScript NodeList to Array?

I&#39;m trying to make a high score table, and suck at arrays in objective c (actually, in general objective c is challenging for me), so I can&#39;t figure out how to sort. I&#39;m trying to do something like this (speudocode, I&#39;m writing this in actionscript style because I&#39;m more comfortable with it):

    highscores.addObjecttoArray(score)
    highscores.sort(ascending)

But I can&#39;t figure it out... I&#39;ve seen other threads about it, but their use plist files and stuff and I don&#39;t know enough objective c to learn from them.

How Do I sort an NSMutable Array with NSNumbers in it?

I&#39;ve been trying to push an item to an associative array like this:

    $new_input[&#39;name&#39;] = array(
        &#39;type&#39; =&gt; &#39;text&#39;, 
        &#39;label&#39; =&gt; &#39;First name&#39;, 
        &#39;show&#39; =&gt; true, 
        &#39;required&#39; =&gt; true
    );
    array_push($options[&#39;inputs&#39;], $new_input);

However, instead of &#39;name&#39; as the key in adds a number. Is there another way to do it?

Push item to associative array in PHP

I have a very simple HTML table with 4 columns: 

    Facility Name, Phone #, City, Specialty

I want the user to be able to sort by **Facility Name** and **City** only.

How can I code this using jQuery?

jQuery table sort

I would like to sort my list with the `date` property.

This is my custom class:

```c#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace Test.Web
{
    public class cTag
    {
        public int id { get; set; }
        public int regnumber { get; set; }
        public string date { get; set; }
    }
}
```

An this is the `List` that I want to sort:

```c#
List&lt;cTag&gt; Week = new List&lt;cTag&gt;();
```

I want to sort the `List` by the `date` property of the `cTag` class.
The date is in the format `dd.MM.yyyy`.

I read something about the `IComparable` interface, but I don&#39;t know how to use it.

Sort a Custom Class List&lt;T&gt;

How can I sort a list by a key described by an arbitrary function?  For example, if I have:

    mylist = [[&quot;quux&quot;, 1, &quot;a&quot;], [&quot;bar&quot;, 0, &quot;b&quot;]]

I&#39;d like to sort &quot;mylist&quot; by the second element of each member, e.g.

    sort(mylist, key=lambda x: x[1])

how can I do this?



Sorting by arbitrary lambda

I&#39;m trying to sort a multidimensional array by multiple keys, and I have no idea where to start. I looked at `uasort()`, but wasn&#39;t quite sure how to write a function for what I need. 

I need to sort by the `state`, then `event_type`, then `date_start`.

My array looks like this:

    [
        [&#39;ID&#39; =&gt; 1, &#39;title&#39; =&gt; &#39;Boring Meeting&#39;,  &#39;date_start&#39; =&gt; &#39;2010-07-30&#39;, &#39;event_type&#39; =&gt; &#39;meeting&#39;, &#39;state&#39; =&gt; &#39;new-york&#39;],
        [&#39;ID&#39; =&gt; 2, &#39;title&#39; =&gt; &#39;Find My Stapler&#39;, &#39;date_start&#39; =&gt; &#39;2010-07-22&#39;, &#39;event_type&#39; =&gt; &#39;meeting&#39;, &#39;state&#39; =&gt; &#39;new-york&#39;],
        [&#39;ID&#39; =&gt; 3, &#39;title&#39; =&gt; &#39;Mario Party&#39;,     &#39;date_start&#39; =&gt; &#39;2010-07-22&#39;, &#39;event_type&#39; =&gt; &#39;party&#39;,   &#39;state&#39; =&gt; &#39;new-york&#39;],
        [&#39;ID&#39; =&gt; 4, &#39;title&#39; =&gt; &#39;Duct Tape Party&#39;, &#39;date_start&#39; =&gt; &#39;2010-07-28&#39;, &#39;event_type&#39; =&gt; &#39;party&#39;,   &#39;state&#39; =&gt; &#39;california&#39;]
    ]

My desired result is:

    [
        [&#39;ID&#39; =&gt; 4, &#39;title&#39; =&gt; &#39;Duct Tape Party&#39;, &#39;date_start&#39; =&gt; &#39;2010-07-28&#39;, &#39;event_type&#39; =&gt; &#39;party&#39;,   &#39;state&#39; =&gt; &#39;california&#39;]
        [&#39;ID&#39; =&gt; 2, &#39;title&#39; =&gt; &#39;Find My Stapler&#39;, &#39;date_start&#39; =&gt; &#39;2010-07-22&#39;, &#39;event_type&#39; =&gt; &#39;meeting&#39;, &#39;state&#39; =&gt; &#39;new-york&#39;],
        [&#39;ID&#39; =&gt; 1, &#39;title&#39; =&gt; &#39;Boring Meeting&#39;,  &#39;date_start&#39; =&gt; &#39;2010-07-30&#39;, &#39;event_type&#39; =&gt; &#39;meeting&#39;, &#39;state&#39; =&gt; &#39;new-york&#39;],
        [&#39;ID&#39; =&gt; 3, &#39;title&#39; =&gt; &#39;Mario Party&#39;,     &#39;date_start&#39; =&gt; &#39;2010-07-22&#39;, &#39;event_type&#39; =&gt; &#39;party&#39;,   &#39;state&#39; =&gt; &#39;new-york&#39;],
    ]

Sort multidimensional array by multiple columns

I have a class called `Order` which has properties such as `OrderId`, `OrderDate`, `Quantity`, and `Total`. I have a list of this `Order` class:

    List&lt;Order&gt; objListOrder = new List&lt;Order&gt;();
    GetOrderList(objListOrder); // fill list of orders

I want to sort the list based on one property of the `Order` object; for example, either by the order date or the order id.

How can I do this in C#?

How to Sort a List&lt;T&gt; by a property in the object

I don&#39;t have much programming experience. But, to me, Struct seems somewhat similar to Hash.

* What can Struct do well?
* Is there anything Struct can do, that Hash cannot do?

After googling, the concept of Struct is important in C, but I don&#39;t know much about C.

When to use Struct instead of Hash in Ruby?

I have two arrays

    a = [:foo, :bar, :baz, :bof]

and

    b = [&quot;hello&quot;, &quot;world&quot;, 1, 2]

I want

    {:foo =&gt; &quot;hello&quot;, :bar =&gt; &quot;world&quot;, :baz =&gt; 1, :bof =&gt; 2}

Any way to do this?

How to build a Ruby hash out of two equally-sized arrays?

How would I go about removing all empty elements (empty list items) from a nested Hash or YAML file?


Removing all empty elements from a hash / YAML?

I am interested in taking an arbitrary dict and copying it into a new dict, mutating it along the way.

One mutation I would like to do is swap keys and value. Unfortunately, some values are dicts in their own right. However, this generates a &quot;unhashable type: &#39;dict&#39;&quot; error. I don&#39;t really mind just stringifying the value and giving it the key. But, I&#39;d like to be able to do something like this:

    for key in olddict:
      if hashable(olddict[key]):
        newdict[olddict[key]] = key
      else
        newdict[str(olddict[key])] = key


Is there a clean way to do this that *doesn&#39;t* involve trapping an exception and parsing the message string for &quot;unhashable type&quot; ?

Asking &quot;is hashable&quot; about a Python value

**Update: Please note I am not asking what a salt is, what a rainbow table is, what a dictionary attack is, or what the purpose of a salt is. I am querying: If you know the users salt and hash, isn&#39;t it quite easy to calculate their password?**

I understand the process, and implement it myself in some of my projects.

    s =  random salt
    storedPassword = sha1(password + s)

In the database you store:

    username | hashed_password | salt

Every implementation of salting I have seen adds the salt either at the end of the password, or beginning:

    hashed_Password = sha1(s + password )
    hashed_Password = sha1(password + s)

Therfore, a dictionary attack from a hacker who is worth his salt (ha ha) would simply run each keyword against the stored salts in the common combinations listed above.

Surely the implementation described above simply adds another step for the hacker, without actually solving the underlying issue?  What alternatives are there to step around this issue, or am I misunderstanding the problem?

The only thing I can think to do is have a secret blending algorithm that laces the salt and password together in a random pattern, or adds other user fields to the hashing process meaning the hacker would have to have access to the database AND code to lace them for a dictionary attack to prove fruitful. (Update, as pointed out in comments it&#39;s best to assume the hacker has access to all your information so this probably isn&#39;t best).

Let me give an example of how I propose a hacker would hack a user database with a list of passwords and hashes:

Data from our hacked database:

    RawPassword (not stored)  |  Hashed   |     Salt
    --------------------------------------------------------
    letmein                       WEFLS...       WEFOJFOFO...

Common password dictionary:

       Common Password
       --------------
       letmein
       12345
       ...

For each user record, loop the common passwords and hash them:

    for each user in hacked_DB
        
        salt = users_salt
        hashed_pw = users_hashed_password
        
        for each common_password
            
            testhash = sha1(common_password + salt)
            if testhash = hashed_pw then
               //Match!  Users password = common_password
               //Lets visit the webpage and login now.
            end if
        
        next
    
    next

I hope this illustrates my point a lot better.

Given 10,000 common passwords, and 10,000 user records, we would need to calculate 100,000,000 hashes to discover as many user passwords as possible.  It might take a few hours, but it&#39;s not really an issue.

**Update on Cracking Theory**

We will assume we are a corrupt webhost, that has access to a database of SHA1 hashes and salts, along with your algorithm to blend them.  The database has 10,000 user records.

[This site][2] claims to be able to calculate 2,300,000,000 SHA1 hashes per second using the GPU.  (In real world situation probably will be slower, but for now we will use that quoted figure).

&gt; (((95^4)/2300000000)/2)*10000 = 177
&gt; seconds

Given a full range of 95 printable ASCII characters, with a maximum length of 4 characters, divided by the rate of calculation (variable), divided by 2 (assuming the average time to discover password will on average require 50% of permutations) for 10,000 users it would take 177 seconds to work out all users passwords where the length is &lt;= 4.

Let&#39;s adjust it a bit for realism.

&gt; (((36^7)/1000000000)/2)*10000 = 2 days

Assuming non case sensitivity, with a password length &lt;= 7, only alphanumeric chars, it would take 4 days to solve for 10,000 user records, and I&#39;ve halved the speed of the algorithm to reflect overhead and non ideal circumstance.

It is important to recognise that this is a linear brute force attack, all calculations are independant of one another, therfore it&#39;s a perfect task for multiple systems to solve.  (IE easy to set up 2 computers running attack from different ends that would half the exectution time).

Given the case of recursively hashing a password 1,000 times to make this task more computationally expensive:

&gt; (((36^7) / 1 000 000 000) / 2) * 1000
&gt; seconds = 10.8839117 hours

This represents a maximum length of 7 alpha-numeric characters, at a less than half speed execution from quoted figure for *one user*.

Recursively hashing 1,000 times effectively blocks a blanket attack, but targetted attacks on user data are still vulnerable.

  [1]: http://saviourc.wordpress.com/2009/09/26/sha1-speed-differences-php-vs-mysql-part-2/
  [2]: http://www.golubev.com/hashgpu.htm

Content Type	Original Author	Original Content on Stackoverflow
Question	Ollie Glass	View Question on Stackoverflow
Solution 1 - Ruby	Stéphan Kochen	View Answer on Stackoverflow
Solution 2 - Ruby	bjg	View Answer on Stackoverflow
Solution 3 - Ruby	AG_	View Answer on Stackoverflow
Solution 4 - Ruby	Mukesh Kumar Gupta	View Answer on Stackoverflow

How do I sort an array of hashes by a value in the hash?

Ruby Problem Overview

Ruby Solutions

Solution 1 - Ruby

Solution 2 - Ruby

Solution 3 - Ruby

Solution 4 - Ruby

IDENTITY_INSERT is set to OFF - How to turn it ON?

How to check with javascript if connection is local host?

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