XStream is a simple java library to serialize objects to XML and back again.
public class Contact { private String name; private List<Address> addresses; public Contact(String name, Address... addresses) { this.name = name; this.addresses = new ArrayList<Address>(Arrays.asList(addresses)); } public Contact(String name, List<Address> addresses) { this.name = name; this.addresses = addresses; } // ... other constructors and methods }
public class Address { private String street; private String city; public Address(String street, String city) { this.street = street; this.city = city; } // ... other constructors and methods }
XStream doesn't care about the visibility of the fields. No getters or setters are needed. Also, XStream does not limit you to having a default constructor.
XStream xStream = new XStream();
In this case you require in the classpath XPP3, a very fast XML pull-parser implementation.
If you do not want to include these dependencies, you can use a standard JAXP DOM parser:
// does not require XPP3 library XStream xStream = new XStream(new DomDriver());
or since Java 6 the integrated StAX parser instead:
// does not require XPP3 library starting with Java 6 XStream xStream = new XStream(new StaxDriver());
To make the XML more concise, you can create aliases for your custom class names to XML element names:
xStream.alias("contact", Contact.class); xStream.alias("address", Address.class);
Create the object:
Address address1 = new Address("My Street", "Bucharest"); Address address2 = new Address("Another Street", "Bucharest"); Contact contact = new Contact("Cristian Sulea", address1, address2);
Convert the object to XML:
String xml = xStream.toXML(contact);
The resulting XML is:
<contact> <name>Cristian Sulea</name> <addresses> <address> <street>My Street</street> <city>Bucharest</city> </address> <address> <street>Another Street</street> <city>Bucharest</city> </address> </addresses> </contact>
Contact contact = (Contact) xStream.fromXML(xml);
All the code in a single class
to make'it easier to copy/paste/run and then play with the code.
package xstream.tutorial; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import com.thoughtworks.xstream.XStream; import com.thoughtworks.xstream.io.xml.DomDriver; public class XStreamTutorial { public static void main(String[] args) { XStream xStream = new XStream(new DomDriver()); xStream.alias("contact", Contact.class); xStream.alias("address", Address.class); Address address1 = new Address("My Street", "Bucharest"); Address address2 = new Address("Another Street", "Bucharest"); Contact contact = new Contact("Cristian Sulea", address1, address2); xStream.toXML(contact, System.out); } public static class Contact { private String name; private List<Address> addresses; public Contact(String name, Address... addresses) { this.name = name; this.addresses = new ArrayList<Address>(Arrays.asList(addresses)); } public Contact(String name, List<Address> addresses) { this.name = name; this.addresses = addresses; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<Address> getAddresses() { return addresses; } public void setAddresses(List<Address> addresses) { this.addresses = addresses; } } public static class Address { private String street; private String city; public Address(String street, String city) { this.street = street; this.city = city; } public String getStreet() { return street; } public void setStreet(String street) { this.street = street; } public String getCity() { return city; } public void setCity(String city) { this.city = city; } } }


min
Syntax
min ( expn , expn )
Description
The min function is used to find the minimum of two numbers (the two expn's). For example, min ( 5, 7 ) is 5. If both numbers are int, the result is int. If both numbers are nat (natural numbers), the result is nat. But if one or both of the numbers are real, the result is real. See also the max function.
Example
This program outputs 74.61.
var x : real := 74.61
var y : real := 85.72
put min ( x, y ) % Outputs 74.61
Example
This program inputs 10 numbers and outputs their minimum.
var m, t : real
get m % Input first number
for i : 2 .. 10 % Handle remaining 9 numbers
get t
m := min ( m, t )
end for
put "The minimum is ", m
See also
See also predefined unit Math.


Ready? Go!
Who cares me the most?
Do you curious about who care you the most? Someone may always pay attention to everything that you posted and leave a comment. No doubt! That person cares you!!
Who liked me the most?
Do you know who will give you "like" the most? Do you want to know who support you the most? Check here and find out your loyal friends!
My Friends' Map
Your friends maybe spread all over the world. Do you want to know how your network looks like on the atlas? Travel with friendsDoc!


I'm a Developer Advocate and Developer Educator with over a decade of experience in Software Engineering.
My main motivation is to empower people through community and technical content.
{{ .employer }}
{{ .title }}{{ $.RenderString .description }}
{{ .technologies }}
{{ .employer }}
{{ .title }}{{ $.RenderString .description }}
{{ .technologies }}
{{ .location }}
{{ .title }}


@(loginForm: Form[Employee])(implicit messages: Messages) @import views.html.helper._ @main("Welcome to Employee Management System with DataBase !!") {


---
layout: post
title: Reading integer input from a text file in C
categories: [programming, io]
excerpt:
tags: [programming, C, IO]
image:
feature:
date: 2015-07-18 04:00:50.000000000 +05:30
modified: 2015-07-18 04:00:50.000000000 +05:30
---
I'm writing this post so that it comes handy whenever I will need this in future.
Many times you need to read from a text file in order to take numeric inputs for problems.
I have used the function fscanf().
{% highlight cpp linenos %}
#include
#include
int main()
{
FILE *textfile=fopen("IntegerArray.txt","r");
int arr[100050],i,lim,num;
if (textfile == NULL)
{
printf("Error Reading File\n");
exit (0);
}
i=0;
while(fscanf(textfile, "%d", &num) >0 )
{
arr[i++]=num;
}
lim=i;
printf("\n Lim : %d \n",lim);
for (i = 0; i < lim; i++)
{
printf("%d : %d\n",i, arr[i]);
}
fclose(textfile);
return 0;
}
{% endhighlight %}


The sphinx site itself looks better than the sites created with the default css, so here we’ll invoke T. S. Eliot’s maxim “Talent imitates, but genius steals” and grab their css and part of their layout. As before, you can either get the required files _static/default.css, _templates/layout.html and _static/logo.png from the website or git (see Fetching the data). Since I did a git clone before, I will just copy the stuff I need from there:
home:~/tmp/sampledoc> cp ../sampledoc_tut/_static/default.css _static/
home:~/tmp/sampledoc> cp ../sampledoc_tut/_templates/layout.html _templates/
home:~/tmp/sampledoc> cp ../sampledoc_tut/_static/logo.png _static/
home:~/tmp/sampledoc> ls _static/ _templates/
_static/:
basic_screenshot.png default.css logo.png
_templates/:
layout.html
Sphinx will automatically pick up the css and layout html files since we put them in the default places with the default names, but we have to manually include the logo in our layout.html. Let’s take a look at the layout file: the first part puts a horizontal navigation bar at the top of our page, like you see on the sphinx and matplotlib sites, the second part includes a logo that when we click on it will take us home and the last part moves the vertical navigation panels to the right side of the page:
{% extends "!layout.html" %}
{% block rootrellink %}

home|

search|

documentation  »

{% endblock %}
{% block relbar1 %}

{{ super() }}
{% endblock %}
{# put the sidebar before the body #}
{% block sidebar1 %}{{ sidebar() }}{% endblock %}
{% block sidebar2 %}{% endblock %}
Once you rebuild the site with a make html and reload the page in your browser, you should see a fancier site that looks like this


Live Updates Of Kogi West Senatorial District Rerun Election
by Enioluwa AdeniyiThe Independent National Electoral Commission is set to conduct the re-run election for the Kogi West Senatorial district.
The people of Kogi West Constituency are ready to vote for the candidate who will represent them in the National Assembly.
The senatorial election which is holding on November 16 is been contested by twenty-four candidates.
The major candidates in the election are Dino Melaye of the Peoples Democratic Party and Smart Adeyemi of the All Progressives Congress.
Naija News will be on the ground to give you the latest information. Keep refreshing the page to get the latest updates.
7:20 AM: Elections are expected to kick off at 8 am across various polling units in the Kogi West Senatorial Districts.
7: 25 AM: Electoral materials have been distributed to some polling units with security operatives on the ground to guard the electoral process.
8: 00 AM: Voters are on the ground at the polling units to check for their names on the register.
9: 00 AM: At the Kabba-Bunu Local Government, Ward: Asuta, Polling Unit, 005, voters are been shown the ballot boxes, indicating red for the governorship election and green for the senatorial election.
9: 10 AM: At Lokoja Local Government Ward: Oworo, Polling unit: Felele Area 004, a report has it that Voting is yet to commence.
9: 20 AM: Kabba/Bunu Ward: Asuta PU: 005, the APO 1 is addressing voters ahead of the commencement of accreditation and voting.
9:31 AM: Kabba/Bunu Ward: Odolu Polling unit code: 005, Voting has started and voters are on queues. Card readers are working well. 7 security officials are on the ground. The voting process is peaceful.
9: 40 AM: Senator Dino Melaye has cast his vote at the polling unit 004, Ayetoro Gbede 1, Ijumu local government area of the state.
10: 00 AM: Dino Melaye gives businesswoman money to share beans cake to voters around the PU 004 in Ayetoro 1 ward in Ijumu LGA.
10: 30 AM: Voting just started at PU 008, ward 01 in Lokoja. Ass. Presiding Officer says delays at the Crowther RAC caused the late start of voting.
10: 35 AM: According to a report, some suspected thugs just snatched electoral materials at Gbeleko polling unit (Kogi state Speaker’s unit) in Egbeda ward of kabba/Bunu local Government.
10: 40 AM: The polling unit where Dino Melaye voted has been attacked by Thugs. The hoodlums who came in a black Hilux van broke one of the ballot boxes and ran away with the other while shooting into the air to scare people away.
11: 00 AM: At Ijumu Local Government area, ward: Aiyetoro 1, PU: 004, a voter has been reportedly shot by thugs and have carted away the ballot box.
11: 10 AM: Kabba/Bunu, Ayeteju Kajola, Ayewa 001 PU, Card reader problem recorded and voting has stopped.
11: 30 AM: A report from SituationRoomNg has it that A SituationRoomNg observer’s phone has been seized by an alleged aide of Gov. Bello for attempting to take pictures of alleged ballot-box stuffing.
12: 00 AM: Smart Adeyemi, the APC Kogi west senatorial candidate, joins the queue to cast his vote at PU 002, Iyara ward, Ijumu LGA.
12: 15 PM: PU 22/12/03/002 Lokoja. Accreditation and Voting going on smoothly. 300 accredited out of 1,165 total registered (25.75%) as at 12:15 pm.
12: 59 PM: Man spotted with numerous PVCs at Lokoja Local Government.
1: 20 PM:
1: 43 PM: Voting has been concluded at the Odole 2, ward 02, PU 02 of Mopa Muro LGA. The officials are just waiting to sort and count the votes.
2: 00 PM:
3: 00 PM: At PUs 001 and 006, Asuta ward, Kabba/Bunu, votes were being counted with the PDP leading when some thugs started pouring water and drinks on the ballot papers. Journalists and INEC ad hoc staff were threatened and chased away.


Composable Async
Create, compose and inject asynchronous behaviors in .Net Framework and .Net Core.
Goal
Create asynchronous behavior such as fiber, rate limiter, circuit breaker.
Compose these behaviors and use them as building blocks with aspect oriented programming.
Provide a lightweight way inject these behaviors to transform POCOs in actors.
Create asynchronous behavior
Asynchronous behaviors are implemented using IDispatcher abstraction.
Composable Async provides various dispatchers implementation:
Retry
// Create dispatcher that catch all ArgumentException and retry for ever with a delay of 200 ms
var retryDispatcher = RetryPolicy.For<ArgumentException>().WithWaitBetweenRetry(TimeSpan.FromSeconds(0.2)).ForEver();
See more at ComposableAsync.Resilient
Circuit-Breaker
// Create dispatcher that catch all ArgumentException and retry for ever with a delay of 200 ms
var retryDispatcher = CircuitBreakerPolicy.For<TimeoutException>().WithRetryAndTimeout(10, TimeSpan.FromMilliseconds(500));
See more at ComposableAsync.Resilient
Fiber
// Create dispatcher that dispatch all action on the same thread
var fiberDispatcher = Fiber.CreateMonoThreadedFiber();
See more at ComposableAsync.Concurrent
RateLimiter
// Create dispatcher that dispatch all action on the same thread
var timeConstraint = TimeLimiter.GetFromMaxCountByInterval(5, TimeSpan.FromSeconds(1));
See more at RateLimiter
Compose dispatchers
Use then extension methods to create a dispatcher that will execute sequentially dispatchers
/// <summary>
/// Returns a composed dispatcher applying the given dispatchers sequentially
/// </summary>
/// <param name="dispatcher"></param>
/// <param name="others"></param>
/// <returns></returns>
public static IDispatcher Then(this IDispatcher dispatcher, IEnumerable<IDispatcher> others)
var composed = fiberDispatcher.Then(timeConstraint);
Use dispatchers
Await dispatcher
await fiberDispatcher;
// After the await, the code executes in the dispatcher context
// In this case the code will execute on the fiber thread
Console.WriteLine($"This is fiber thread {Thread.CurrentThread.ManagedThreadId}");
As httpDelegateHandler
Transform a dispatcher into HttpMessageHandler with AsDelegatingHandler extension method:
/// Using time limiter nuget
var handler = TimeLimiter
.GetFromMaxCountByInterval(60, TimeSpan.FromMinutes(1))
.AsDelegatingHandler();
var client = new HttpClient(handler);
As wrapper for proxy Factory
Using ComposableAsync.Factory
, with this option all methods call to the proxyfied object are wrapped using the provided dispatcher.
var retryDispatcher = RetryPolicy.For<SystemException>().ForEver();
var originalObject = new BusinessObject();
var proxyFactory = new ProxyFactory(retryDispatcher);
var proxyObject = proxyFactory.Build<IBusinessObject>(originalObject);
// The call to the originalObject will be wrapped into a retry policy for SystemException
var res = await proxyObject.Execute(cancellationToken);
Actors
ComposableAsync.Concurrent
also provides an actor factory based on fiber and proxy factory.
// Instantiate actor factory
var builder = new ActorFactoryBuilder();
var factory = builder.GetActorFactory(shared: false);
// When shared is true, all actor leaves in the same thread,
// when shared is false, each actor leaves in its own thread.
// Instantiate an actor from a POCO
var fooActor = fact.Build<IFoo>(new ConcreteFoo());
See more at ComposableAsync.Concurrent
Nuget
For core functionality:
Install-Package ComposableAsync.Core
For factories:
Install-Package ComposableAsync.Factory
For actors:
Install-Package ComposableAsync.Concurrent
For retry and circuit-breaker:
Install-Package ComposableAsync.Resilient


Welcome to Pat's Salmon Cookies. We are a small, family owned, gourmet cookie company in Seattle.Here you can find the best homemade, delicious, and fabulous cookies . Our signature salmon cookies and other delicious cookies came from Pat's secret menu. All of the ingredients are local, fresh, and organic. They are carefully selected and baked with our passion.Try it and you will love it!


Carousel
This pattern contains:
molecules-inset-block
HTML

Lorem ipsum dolor sit (37 characters)

←

1/5

→

Work Form
HTML
<form action="#" method="post" class="para-form">

Hello. How’s it going your name
<input required="true" class="inline" id="name" name="name" type="text" placeholder="your name">? I know things have never been more exciting than they are now at your company
<input class="inline" id="company" name="company" type="text" placeholder="your company">. You know I’m really happy to see you stopped by to tell us about your reason for contacting <select id="reason" class="inline" name="reason">
<option selected="" disabled="" value="">your reason for contacting</option>
<option value="Scheduling a workshop">scheduling a workshop</option>
<option value="Design consulting">design consulting</option>
<option value="Just saying hello!">what you’re up to :)</option>
</select>. I’ll send you an e-mail at <input class="inline" required="true" id="email" name="email" type="email" placeholder="your e-mail"> so we can talk it over.

If you have time, tell us more about that:
<textarea name="more-information" id="more-information"></textarea>
<input type="submit" class="btn btn-large" name="Contact" value="Fire Away">
</form>


| 1100 | (A) | and faste hyes owte of the Oste with aughte hundrethe speris |
| 1104 | (C) | He houede with-oute þe chase . with .viij. hondred speres |
| 1086 | (D) | And yssued out of þe oost wiþ viij. C speris |
| 1067 | (E) | & issued out of þe oost . with eyȝt hundred speres |
| 59 | (Ex) | . . . viijC sperys |
| 1124 | (L) | and dissed out of þe ost with eȝte hundred speres |
| 1036 | (P) | A nd hyes oute of . . . |
| 1076 | (U) | And issed out of the host / with an hundred speres |
| 165 | (V) | And Issues oute of þe oost with C speres |


Please use the following mediums to contact me!
+94711883899,+94762967014
kaweendras.github.io
http://salithak1@gmail.com


<<more code about KGame, an easy example>>
A network game is a game with usually several players, that are on different computers. These computers are usually connected to the internet, and all the moves a player does are exchanged over this network.
The exchange of moves and other information is done using the class KMessageServer. An object of this class is a server that waits for connections. Someone who wants to take part in the game has to connect to this server - usually using an internet socket connection. He does this by creating a KMessageClient object. This object connects to the message server.
The transfer of data is realised by subclasses of the abstract class KMessageIO. One object of this class is created on the client side, one on the server side. Different types of networks can be supported by creating new subclasses of KMessageIO. There are already two subclasses of KMessageIO: KMessageSocket uses a internet socket connection to transfer the data from the message client to the message server or vice versa. KMessageDirect can be used if both the message server and the message client are within the same process. The data blocks are copied directly to the other side, so the transfer is faster and needs no network bandwidth.
A typical network game situation could look like this:
Here, three KGame object (called message clients) are connected to the KMessageServer object. One is in the same process, so it uses KMessageDirect. The other two use KMessageSocket, so an internet socket connection is used. KGame doesn't talk directly to the message server, but uses a KMessageClient object instead. One of the KMessageClient objects is the admin of the message server. This client has some priviledges. It may e.g. kill the connection to other message clients, or limit the number of clients that may connect.
The KGame objects are by default all equal. So the usual approach will be that every KGame object will store the complete status of the game, and any change or move will be broadcasted to the other KGame objects, so that they all change the status in identical ways. Sometimes it may be necessary (or just easier to implement) that one KGame object is a game server (i.e. he is repsonsible for everything, he coordinates the complete game and stores the game status), whereas the other KGame objects are only dumb stubs that are used to contact the game server. You can implement both approaches using the message server structure. If you need to elect the KGame object that shall be the game server, you may e.g. use the one that has the KMessageClient that is the admin of the message server. (Of course this is only a suggestion, you can use other approaches.)
The main principle when developing the message server/client structure was, that the message server doesn't have any idea of the game and its rules that is played. The message server only forwards messages from one message client to the others without interpreting or manipulating the data. So always keep in mind that the message server is not a game server! It does not store any data about the game status. It is only a server for network connections and message broadcasting, not for game purposes. The reason for this principle is, that any game can be played using a KMessageServer on any computer. The computer being the message server doesn't need to know anything about the game that is played on it. So you don't have to install new versions of the game there. Only the clients need to be game specific.
Usually you don't need to create KMessageServer or KMessageClient objects in your game, since KGame does this for you. There are three different scenarios fo network games that are all supported in KGame:
Scenario 1: local game
The local game should always be the default state a game should be in. To avoid having this scenario as a special case, KGame automatically creates a KMessageServer object and a KMessageClient object. So every change and every move is sent to the message server and is returned to the KGame object before it is processed. Since the connection between the message client and the message server uses KMessageDirect the data transfer is very fast and wont hurt in most cases.
This is the default situation right after creating the KGame object.
Scenario 2: network game, started by one player
If one user is bored of playing alone, he can open his game for connections from the outside world. He listens to a TCP/IP socket port (i.e. a number between 0 and 65535). Other players can create KGame objects of their own and connect to this port. They need to know the IP address of that computer and the port number. This situation will have this structure:
The first player has to do something like:
KGame *myGame = new KGame (); // wait for connections on port 12345 myGame->offerConnections (12345);And the other players have to do something like:
KGame *myGame = new KGame (); // connect to the message server myGame->connectToServer ("theServer.theDomain.com", 12345);This automatically removes the message server in these KGame objects and connects to the given one instead.
Scenario 3: network game, using a stand alone message server
Sometimes it is not possible to let the message server run on one of the players computer. If e.g. all the players have their computer in a local network that uses masquerading to contact the internet, other computers cannot connect to them since the computer doesn't have a IP address to the outside world. Then the only way to play a network game is to have a standalone KMessageServer object on another server computer (somthing like "games.kde.org" e.g.). Since the KMessageServer isn't game specific at all, every game can be played using it. There doesn't have to be any special software installed on that server computer, only the program creating a KMessageServer object.
This scenario has some more advantages: The message server can be a well known meeting point to start a game. This way one could play games against other players you never knew before. Furthermore the game is stopped brutally when the program that contains the message server in scenario 2 is quitted. (Migration of message servers is not yet implemented, but may be in the future.) Using a stand alone message server, the players may enter and leave the game as they want.
To create this scenario, a special KMessageServer program has to be started on the computer that shall be the stand alone message server:
% kmessageserver -port=12345The other games that want to connect have to do this (supposed the stand alone message server has the IP address "games.kde.org"):
KGame *myGame = new KGame (); // connect to the message server myGame->connectToServer ("games.kde.org", 12345);


"Professor S"
def get_resource_type_from_included_serializer(self):
"""
Check to see it this resource has a different resource_name when
included and return that name, or None
"""
field_name = self.field_name or self.parent.field_name
parent = self.get_parent_serializer()
if parent is not None:
# accept both singular and plural versions of field_name
field_names = [
inflection.singularize(field_name),
inflection.pluralize(field_name)
]
includes = get_included_serializers(parent)
for field in field_names:
if field in includes.keys():
return get_resource_type_from_serializer(includes[field])
return None
Test your performance critical code


?The
New
York
Botanical
Garden
Cajanus
cajan
(L.)
Huth
PLANTS
OF
BAHAMA
ISLANDS
Cajanus
cajan
(L.)
Millsp
pigeon
pea
North
Andros:
in
coppice
along
Queen's
Highway
just
south
of
Fresh
Creek
airport
Woody
herb
1.5
m
tall;
flowers
yellow;
edge
of
roadway.
1616213
Legend -
Level of confidence that token is an accurately-transcribed word
extremely low
very low
low
undetermined
medium
high
very high


We do not use your contact or identity information except on the app/device. We never store it anywhere which is accessible to us or public. We absolutely do not share any information with any parties, third-party providers, targeters or for that manner any entity.


Params
Size:
Apply
Benchmarks
Reset
Baseline (plain components)
Run
Cost of decorators
Run
Cost of dynamic components
Run
$SCRIPTS$


Command Handler
Background
A Command Handler handles commands. The command handler is responsible for executing the appropriate methods on Aggregate Roots and Domain Services to fulfill the intent of the Command.
Requirements
A Command Handler must implement the IHandleCommands interface. This is a simple marker interface with no methods to implement.
To handle a Command, you simply create a method called Handle with a single parameter of the Command you wish to handle. A Command Handler does not return anything. It is not permitted to return a value from a Command. When a Command is executed, you will receive a CommandResult which will indicate whether the Command succeeded and, in the case of failure, why the Command failed. No artifacts that were created or updated as a result of the Command will be present on the CommandResult.
public void Handle(AddRecommendationToCart cmd)
There MUST be a single handler for a Command. doLittle will throw an exception if there is no handler for a command or if there is more than one handler for a command. There can only be a single handler for a command as there must be a clear and unambiguous indication of the result of the execution of the command. Multiple command handlers for a single command would require co-ordination of multiple results with associated rollback of successful handlers after unsuccessful ones. Where you wish multiple things to happen on receipt of a Command, you must implement and handle this yourself in your Command Handler.
Responsibilities
The sole responsibility of the Command Handler is to execute the Command.
A Command Handler should not implement any validation, security checks, or such like. These should be handled earlier in the command pipeline. When we invoke a Command Handler, it is with the expectation that the action will succeed. We should have validated the command, should checked business rule conditions, should checked the permissions and therefore the command should succeed. It is for this reason that within a Command Handler, the only way to indicate that the Command did not succeed is via an Exception. This is because, due to our previous checks, it is truly an exceptional condition for the Command to fail.
Design
It is recommended that a CommandHandler should invoke a single method on Aggregate Root. This is an indication that you have correctly modelled your Aggregate Root, Command and business transaction. It is sometimes useful to think of a Command as a serialized call on a method on an Aggregate Root.
As nothing can be returned from a Command Handler, it is recommended against relying on database generated identities or keys. You will not be able to receive the Id generated by the database. It is recommended to use non-meaningful keys such as Guids on a Command which can be provided by the invoker of the Command and Command Handler. Where a database generated key is required, it is recommended to include another candidate key that can be provided by the caller.


Resources:
RubyonRails APIBackground
In phase 2 of DevBootCamp, we are required to do a series of 10 solo portfolio challenges. One of the challenges requires us to do a join table in AR as well as some other things. Let's take a look at the files below.
This post will be a review of Associations, Validations, and Join tables in AR.
Workflow
- Use rake commands (generate, db, seed) to create migration and model files.
- Create the schemas of the migration files. This is part 1 of where you set up the joins. The first image below is your joins migraion, the ones after are the other migrations.
- Create the Associations and Validations in your models. The first image below is the joins model. Notice how we have two belongs_to associations. The other following images link to the joins table(has_many :levels) and link through the joins table to the other model.


MapRectangle QML Type
The MapRectangle type displays a rectangle on a Map. More...
| Import Statement: | import QtLocation 5.3 |
| Since: | Qt Location 5.5 |
Properties
- border
- border.width : int
- border.color : color
- bottomRight : coordinate
- color : color
- opacity : real
- topLeft : coordinate
Detailed Description
The MapRectangle type displays a rectangle on a Map. Rectangles are a special case of Polygon with exactly 4 vertices and 4 "straight" edges. In this case, "straight" means that the top-left point has the same latitude as the top-right point (the top edge), and the bottom-left point has the same latitude as the bottom-right point (the bottom edge). Similarly, the points on the left side have the same longitude, and the points on the right side have the same longitude.
To specify the rectangle, it requires a topLeft and bottomRight point, both given by a coordinate.
 This can be changed using the color, border.color and border.width properties.
Note: Similar to the MapPolygon type, MapRectangles are geographic items, thus dragging a MapRectangle causes its vertices to be recalculated in the geographic coordinate space. Apparent stretching of the item occurs when dragged to the a different latitude, however, its edges remain straight.
Performance
MapRectangles have a rendering cost identical to a MapPolygon with 4 vertices.
Like the other map objects, MapRectangle is normally drawn without a smooth appearance. Setting the opacity property will force the object to be blended, which decreases performance considerably depending on the hardware in use.
Example Usage
The following snippet shows a map containing a MapRectangle, spanning from (-27, 153) to (-28, 153.5), near Brisbane, Australia. The rectangle is filled in green, with a 2 pixel black border.
Map { MapRectangle { color: 'green' border.width: 2 topLeft { latitude: -27 longitude: 153 } bottomRight { latitude: -28 longitude: 153.5 } } }
Property Documentation
This property is part of the border property group. The border property group holds the width and color used to draw the border of the rectangle. The width is in pixels and is independent of the zoom level of the map.
The default values correspond to a black border with a width of 1 pixel. For no line, use a width of 0 or a transparent color.
bottomRight : coordinate |
This property holds the bottom-right coordinate of the MapRectangle which can be used to retrieve its longitude, latitude and altitude.
This property holds the fill color of the rectangle. For no fill, use a transparent color.
This property holds the opacity of the item. Opacity is specified as a number between 0 (fully transparent) and 1 (fully opaque). The default is 1.
An item with 0 opacity will still receive mouse events. To stop mouse events, set the visible property of the item to false.
topLeft : coordinate |
This property holds the top-left coordinate of the MapRectangle which can be used to retrieve its longitude, latitude and altitude.


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Britain's Prince Andrew speaks over his relationship with Jeffrey Epstein
by NewstalkThe British royal Prince Andrew has spoken publicly for the first time about his relationship with convicted US sex offender Jeffrey Epstein.
The son of Queen Elizabeth II says he "let the side down" as a member of the British royal family.
The scandal involving the American billionaire and allegations against the prince have led Buckingham Palace to issue a number of unexpected statements in the past four years - denying the prince had sex with a 17-year-old girl and that he knew anything of Epstein's crimes against underage girls.
In an interview with BBC's Newsnight, due to be aired on Saturday, he was asked about why he stayed with Epstein after the billionaire had admitted having sex with an underage girl.
Prince Andrew said: "I stayed with him and that's... that, as it were, I kick myself for on a daily basis because it was not something that was becoming of a member of the royal family and we try and uphold the highest standards and practices and I let the side down, simple as that."
Video taken in 2010 showed Prince Andrew looking out of the door of Epstein's mansion in New York as he was staying with the billionaire.
 Photos were also taken of the two men walking in Central Park.
Those close to the prince say he had gone to America to tell Epstein that they could no longer be friends.
In the interview, he is also asked about allegations made by one of Epstein's victims - Virginia Roberts - who claims she was made to have sex with Prince Andrew when she was 17-years-old, after a night out in London.
When asked for his response to those claims he said: "I have no recollection of ever meeting this lady, none whatsoever."
When asked: "You don't remember meeting her?" He replied: "No".
As Epstein faced trial in America this summer and then killed himself in a Manhattan jail, the scandal again erupted around Prince Andrew.
On Twitter, Prince Andrew ex-wife Sarah Ferguson said: "It is so rare to meet people that are able to speak from their hearts with honesty+pure real truth, that remain steadfast and strong to their beliefs.
"Andrew is a true+real gentleman and is stoically steadfast to not only his duty but also his kindness + goodness".
Lawyers acting for Epstein's victims still have questions about what the prince and Epstein's other high-profile friends knew about the billionaire's crimes.
Prince Andrew has denied witnessing or suspecting any behaviour of the sort that subsequently led to Epstein's arrest and conviction.


| result | {{validate$pass}} |
| error target |
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| withdraw |
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| decimal | |
| not required & empty & other rules not pass | |
| name | |
| mobile(regular) | |
| age | {{employee.age}} {{employee.age}} |
| phone | |
| number-max-min | |
| length | |
| id card | |
| address | {{address}} {{address}} |
| description | |


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15) Eigenvectors and Eigenvalues¶
Related references:
One of the most important problems in linear algebra:¶
(also called a characteristic value or latent root), and x is the corresponding eigenvector or characteristic vector. We disregard the trivial solution of x = 0 and \(\lambda = 0\).
Thus, multiplying x by A scales x by \(\lambda\).
The set of eigenvalues is called the spectrum of A. The largest of the absolute values of the eigenvalues of A is called the spectral radius of A.
The set of all eigenvectors corresponding to an eigenvalue of A, together with 0, forms a vector space called the eigenspace of A corresponding to this eigenvalue.
The problem of determining eigenvalues and eigenvectors (called an eigenvalue problem) has many applications, some of which we will discuss after getting through some terminology and mechanics.
This and other comics from The Manga Guide to Linear Algebra
But how do we solve these equations?¶
We rearrange our system of
And Cramer’s Theorem (covered last lecture) states that this homogeneous system of equations has a nontrivial solution if and only if the corresponding determinant of the coefficients is zero.
This special determinent, \(D(\lambda)\), is called the characteristic determinant:
In this case, the characteristic determinant is:
After expanding, we get the characteristic equation or characterisic polynomial:
Theorem: The eigenvalues of a square matrix A are the roots of the characteristic equation of A. Hence an \(n \times n\) matrix has at least one eigenvalue and at most \(n\) numerically different eigenvalues.
Eigenvalues are determined first. Then we find the eigenvectors.
Theorem: If x is an eigenvector of a matrix A corresponding to an eigenvalue \(\lambda\), so is \(k\)x with any \(k \neq 0\).
In [1]:
# Even easier: make the computer compute them!
import numpy as np
a = np.array([[8, -3], [2, 1]])
eigenvalues, eigenvectors = np.linalg.eig(a)
In [2]:
print(eigenvalues)
[ 7. 2.]
In [3]:
# eigenvectors are normalized (unit “length”) eigenvectors
print(eigenvectors)
[[ 0.9486833 0.4472136 ]
[ 0.31622777 0.89442719]]
In [4]:
eigval1 = eigenvalues[0]
eigval2 = eigenvalues[1]
# eigenvectors are displayed such that the column v[:,i] is
# the eigenvector corresponding to the eigenvalue w[i].
eigvec1 = eigenvectors[:, 0]
eigvec2 = eigenvectors[:, 1]
In [5]:
# Always a good idea to check our work:
left_check = np.matmul(a, eigvec1)
right_check = eigval1 * eigvec1
if np.allclose(left_check, right_check):
print("The first eigenvalue ({}) \n "
"pairs with eigenvector {}".format(eigval1, eigvec1))
The first eigenvalue (7.0)
pairs with eigenvector [ 0.9486833 0.31622777]
In [6]:
left_check = np.matmul(a, eigvec2)
right_check = eigval2 * eigvec2
if np.allclose(left_check, right_check):
print("The first eigenvalue ({}) \n "
"pairs with eigenvector {}".format(eigval2, eigvec2))
The first eigenvalue (2.0)
pairs with eigenvector [ 0.4472136 0.89442719]
All diagonalizable \(n\times n\) matrices always have \(n\) linearly independent eigenvectors. In other words, there is always a basis in \(R^n\) consisting solely of eigenvectors, called an eigenbasis.
However, there are not always \(n\) unique eigenvalues!
In [7]:
a = np.array([[-2, 2, -3], [2, 1, -6], [-1, -2, 0]])
eigenvalues, eigenvectors = np.linalg.eig(a)
print(eigenvalues)
[-3. 5. -3.]
How does this happen?
In [8]:
mult_sol_d = a + 3*np.eye(3)
print(mult_sol_d)
[[ 1. 2. -3.]
[ 2. 4. -6.]
[-1. -2. 3.]]
Which reduces to:
From this we can get 2 linearly independent eigenvectors if we use $x_2 =1 $ and \(x_3 = 1\) for one eigenvector with eigenvalue of -3, and use \(x_2 = 0\) and \(x_3 = 1\) for the other. That is:
Those are not the only bases that can be used. Let’s see what NumPy chose, and then validate the solutions.
In [9]:
print(eigenvectors)
[[-0.95257934 0.40824829 -0.05430304]
[ 0.27216553 0.81649658 0.83908241]
[-0.13608276 -0.40824829 0.54128726]]
In [10]:
for i in range(3):
left_check = np.matmul(a, eigenvectors[:, i])
right_check = eigenvalues[i] * eigenvectors[:,i]
if np.allclose(left_check, right_check):
print("The eigenvalue {:.2f} \n "
"pairs with eigenvector {}".format(eigenvalues[i],
eigenvectors[:, i]))
else:
print(left_check)
print(right_check)
The eigenvalue -3.00
pairs with eigenvector [-0.95257934 0.27216553 -0.13608276]
The eigenvalue 5.00
pairs with eigenvector [ 0.40824829 0.81649658 -0.40824829]
The eigenvalue -3.00
pairs with eigenvector [-0.05430304 0.83908241 0.54128726]
In [11]:
# Now validating our hand solution:
x_0 = np.array([-2, 1, 0])
x_2 = np.array([3, 0, 1])
left_check = np.matmul(a, x_0)
right_check = eigenvalues[0] * x_0
if np.allclose(left_check, right_check):
print("The eigenvalue {:.2f} \n could alternately pair"
"with eigenvector {}".format(eigenvalues[0], x_0))
left_check = np.matmul(a, x_2)
right_check = eigenvalues[2] * x_2
if np.allclose(left_check, right_check):
print(" and the orthogonal "
"eigenvector {}".format(x_2))
The eigenvalue -3.00
could alternately pairwith eigenvector [-2 1 0]
and the orthogonal eigenvector [3 0 1]
The order \(M_A\) of an eigenvalue \(\lambda\) as a root of the characteristic polynomial is the algebraic multiplicity of \(\lambda\).
The number \(m_{\lambda}\) of linearly independent eigenvectors corresponding to \(\lambda\) is the geometric multiplicity of \(\lambda\). Thus, \(m_{\lambda}\) is the dimension of the eigenspace corresponding to this \(\lambda\).
Since the characteristic polynomial has degree \(n\), the sum of all algebraic multiplicities must equal \(n\).
Can real matrices get complex?¶
In [12]:
a = np.array([[0, 1], [-1, 0]])
eigenvalues, eigenvectors = np.linalg.eig(a)
print(eigenvalues)
[ 0.+1.j 0.-1.j]
In [13]:
print(eigenvectors)
[[ 0.70710678+0.j 0.70710678-0.j ]
[ 0.00000000+0.70710678j 0.00000000-0.70710678j]]
In general, for $ :raw-latex:`\mathbf{A}` = :raw-latex:`\left[ \begin{array}{cc} a & b \\ -b & a \end{array} \right] `$, $ :raw-latex:`mathbf{A}`$ has eigenvectors \(a +ib\) and \(a-ib\).
Next up: Basic stats and probability!
Permutations¶
Choosing three from n items in a certain order creates a permutation of the chosen items. The number of possible permutations of k objects chosen among n objects is written as: $ _nP_k $ The number of ways k objects can be chosen among n possible ones is equal to:
Combinations¶
Choosing k among n items without considering the order in which they are chosen is called a combination. The number of different ways this can be done is written by using the binomial coefficient notation: $ {n:raw-latex:choose `k} $ or :math:`_nC_r which is read “n choose k.”
When the order doesn’t matter, it is a Combination.
When the order does matter it is a Permutation. A Permutation is an ordered Combination.