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• Five Fake Sounds Engineered to Make Your Feel Better [Science]

  - by Jason Fitzpatrick

  As objects in our environment (like cars, ATMs, and phones) have grown lighter and quieter scientists have been carefully engineering their sounds so that they continue to sound like we expect them to. Read on to see how. At the design blog Humans Invent they share five interesting ways that the world around us is being engineered so it sounds the way we expect it to. They start with the example of the car door. Years ago cars were almost entirely steel, the doors were weighty, and when you slammed them it sounded like one big hunk of steel locking into another big hunk of steel (which, in fact, it was). Newer cars are lighter but people still crave that substantial clunk. Humans Invent highlights the effect of consumer desire: A car door is essentially a hollow shell with parts placed inside it. Without careful design the door frame amplifies the rattling of mechanisms inside. Car companies know that if buyers don’t get a satisfying thud when they close the door, it dents their confidence in the entire vehicle. To produce the ideal clunk, car doors are designed to minimise the amount of high frequencies produced (we associate them with fragility and weakness) and emphasise low, bass-heavy frequencies that suggest solidity. The effect is achieved in a range of different ways – car companies have piled up hundreds of patents on the subject – but usually involves some form of dampener fitted in the door cavity. Locking mechanisms are also tailored to produce the right sort of click and the way seals make contact is precisely controlled. On average it takes 1.8 seconds to close a car door but in that time you’re witnessing a strange kind of symphony composed by engineers and designers whose goal is to reassure you that its rock solid. They mention lock mechanisms, something you may never have thought about. A friend of mine had a Ford Focus some years ago and that particular model had electric locks that, instead of giving a satisfying thunk or solid click, made this horrible gates-of-the-prison-buzzing sound that was completely unnerving. Hit up the link below to see how sounds are engineered for car doors, electric motors, ATM machines, and more. 5 Fake Sounds Designed to Help Humans [Humans Invent via Boing Boing] How To Easily Access Your Home Network From Anywhere With DDNSHow To Recover After Your Email Password Is CompromisedHow to Clean Your Filthy Keyboard in the Dishwasher (Without Ruining it)

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• INNER JOIN Returns Too Many Results

  - by Alon

  I have the following SQL: SELECT * FROM [Database].dbo.[TagsPerItem] INNER JOIN [Database].dbo.[Tag] ON [Tag].Id = [TagsPerItem].TagId WHERE [Tag].Name IN ('home', 'car') and it returns: Id TagId ItemId ItemTable Id Name SiteId 1 1 1 Content 1 home 1 2 1 2 Content 1 home 1 3 1 3 Content 1 home 1 4 2 4 Content 2 car 1 5 2 5 Content 2 car 1 6 2 12 Content 2 car 1 instead of just two records, which these names are "home" and "car". How can I fix it? Thanks.

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• How can I edit an entity in MVC4 with EF5 which has a unique constraint?

  - by Yoeri

  [HttpPost] public ActionResult Edit(Car car) { if (ModelState.IsValid) { db.Entry(car).State = EntityState.Modified; db.SaveChanges(); return RedirectToAction("Index"); } return View(car); } This is a controller method scaffolded by MCV 4 My "car" entity has a unique field: LicensePlate. I have custom validation on my Entity: Validation: public partial class Car { partial void ValidateObject(ref List<ValidationResult> validationResults) { using (var db = new GarageIncEntities()) { if (db.Cars.Any(c => c.LicensePlate.Equals(this.LicensePlate))) { validationResults.Add( new ValidationResult("This licenseplate already exists.", new string[]{"LicensePlate"})); } } } } should it be usefull, my car entity: public partial class Car:IValidatableObject { public int Id { get; set; } public string Color { get; set; } public int Weight { get; set; } public decimal Price { get; set; } public string LicensePlate { get; set; } public System.DateTime DateOfSale { get; set; } public int Type_Id { get; set; } public int Fuel_Id { get; set; } public virtual CarType Type { get; set; } public virtual Fuel Fuel { get; set; } public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) { var result = new List<ValidationResult>(); ValidateObject(ref result); return result; } partial void ValidateObject(ref List<ValidationResult> validationResults); } QUESTION: Everytime I edit a car, it raises an error: Validation failed for one or more entities. See 'EntityValidationErrors' property for more details. The error is the one raised by my validation, saying it can't edit because there is already a car with that license plate. If anyone could point me in the right direction to fix this, that would be great! I searched but couldn't find anything, so even related posts are welcome!

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• Java complex validation in Dropwizard?

  - by miku

  I'd like to accept JSON on an REST endpoint and convert it to the correct type for immediate validation. The endpoint looks like this: @POST public Response createCar(@Valid Car car) { // persist to DB // ... } But there are many subclasses of Car, e.g. Van, SelfDrivingCar, RaceCar, etc. How could I accept the different JSON representations on the endpoint, while keeping the validation code in the Resource as concise as something like @Valid Car car? Again: I send in JSON like (here, it's the representation of a subclass of Car, namely SelfDrivingCar): { "id" : "t1", // every Car has an Id "kind" : "selfdriving", // every Car has a type-hint "max_speed" : "200 mph", // some attribute "ai_provider" : "fastcarsai ltd." // this is SelfDrivingCar-specific } and I'd like the validation machinery look into the kind attribute, create an instance of the appropriate subclass, here e.g. SelfDrivingCar and perform validation. I know I could create different endpoints for all kind of cars, but thats does not seem DRY. And I know that I could use a real Validator instead of the annotation and do it by hand, so I'm just asking if there's some elegant shortcut for this problem.

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• Why doesn't is operator take in consideration if the explicit operator is overriden when checking ty

  - by Galilyou

  Hey Guys, Consider this code sample: public class Human { public string Value { get; set;} } public class Car { public static explicit operator Human (Car c) { Human h = new Human(); h.Value = "Value from Car"; return h; } } public class Program { public static void Mani() { Car c = new Car(); Human h = (Human)c; Console.WriteLine("h.Value = {0}", h.Value); Console.WriteLine(c is Human); } } Up I provide a possibility of an explicit cast from Car to Human, though Car and Human hierarchically are not related! The above code simply means that "Car is convertible to human" However, if you run the snippet you will find the expression c is Human evaluates to false! I used to believe that the is operator is kinda expensive cause it attempts to do an actual cast that might result in an InvalidCastException. If the operator is trying to cast, then the cast should succeed as there's an operator logic that should perform the cast! What does "is" test? Does test a hierarchical "is-a" relationship? Does test whether a variable type is convertible to a type?

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• Where should I put contextual data related to an Object that is not really a property of the object?

  - by RenderIn

  I have a Car class. It has three properties: id, color and model. In a particular query I want to return all the cars and their properties, and I also want to return a true/false field called "searcherKnowsOwner" which is a field I calculate in my database query based on whether or not the individual conducting the search knows the owner. I have a database function that takes the ID of the searcher and the ID of the car and returns a boolean. My car class looks like this (pseudocode): class Car{ int id; Color color; Model model; } I have a screen where I want to display all the cars, but I also want to display a flag next to each car if the person viewing the page knows the owner of that car. Should I add a field to the Car class, a boolean searcherKnowsOwner? It's not a property of the car, but is actually a property of the user conducting the search. But this seems like the most efficient place to put this information.

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• Serializing Configurations for a Dependency Injection / Inversion of Control

  - by Joshua Starner

  I've been researching Dependency Injection and Inversion of Control practices lately in an effort to improve the architecture of our application framework and I can't seem to find a good answer to this question. It's very likely that I have my terminology confused, mixed up, or that I'm just naive to the concept right now, so any links or clarification would be appreciated. Many examples of DI and IoC containers don't illustrate how the container will connect things together when you have a "library" of possible "plugins", or how to "serialize" a given configuration. (From what I've read about MEF, having multiple declarations of [Export] for the same type will not work if your object only requires 1 [Import]). Maybe that's a different pattern or I'm blinded by my current way of thinking. Here's some code for an example reference: public abstract class Engine { } public class FastEngine : Engine { } public class MediumEngine : Engine { } public class SlowEngine : Engine { } public class Car { public Car(Engine e) { engine = e; } private Engine engine; } This post talks about "Fine-grained context" where 2 instances of the same object need different implementations of the "Engine" class: http://stackoverflow.com/questions/2176833/ioc-resolve-vs-constructor-injection Is there a good framework that helps you configure or serialize a configuration to achieve something like this without hard coding it or hand-rolling the code to do this? public class Application { public void Go() { Car c1 = new Car(new FastEngine()); Car c2 = new Car(new SlowEngine()); } } Sample XML: <XML> <Cars> <Car name="c1" engine="FastEngine" /> <Car name="c2" engine="SlowEngine" /> </Cars> </XML>

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• MySQL Multiple Table Join

  - by hitman001

  I have a 3 tables that I'm trying to join and get distinct results. CREATE TABLE `car` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) NOT NULL DEFAULT '', PRIMARY KEY (`id`) ) ENGINE=InnoDB mysql> select * from car; +----+-------+ | id | name | +----+-------+ | 1 | acura | +----+-------+ CREATE TABLE `tires` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `tire_desc` varchar(255) DEFAULT NULL, `car_id` int(10) unsigned NOT NULL, PRIMARY KEY (`id`), KEY `new_fk_constraint` (`car_id`), CONSTRAINT `new_fk_constraint` FOREIGN KEY (`car_id`) REFERENCES `car` (`id`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB mysql> select * from tires; +----+-------------+--------+ | id | tire_desc | car_id | +----+-------------+--------+ | 1 | front_right | 1 | | 2 | front_left | 1 | +----+-------------+--------+ CREATE TABLE `lights` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `lights_desc` varchar(255) NOT NULL, `car_id` int(10) unsigned NOT NULL, PRIMARY KEY (`id`), KEY `new1_fk_constraint` (`car_id`), CONSTRAINT `new1_fk_constraint` FOREIGN KEY (`car_id`) REFERENCES `car` (`id`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB mysql> select * from lights; +----+-------------+--------+ | id | lights_desc | car_id | +----+-------------+--------+ | 1 | right_light | 1 | | 2 | left_light | 1 | +----+-------------+--------+ Here is my query. mysql> SELECT name, group_concat(tire_desc), group_concat(lights_desc) FROM car left join tires on car.id = tires.car_id left join lights on car.id = car_id group by car.id; +-------+-----------------------------------------------+-----------------------------------------------+ | name | group_concat(tire_desc) | group_concat(lights_desc) | +-------+-----------------------------------------------+-----------------------------------------------+ | acura | front_right,front_right,front_left,front_left | right_light,left_light,right_light,left_light | +-------+-----------------------------------------------+-----------------------------------------------+ I get duplicate entires and this is what I would like to get. +-------+-----------------------------------------------+--------------------------------+ | name | group_concat(tire_desc) | group_concat(lights_desc) | +-------+-----------------------------------------------+--------------------------------+ | acura | front_right,front_left | right_light,left_light | +-------+-----------------------------------------------+--------------------------------+ I cannot use distinct in group_concat because I might have legitimate duplicates which I would like to keep. Is there any way to do this query using joins and not using inner selects like the statement below? SELECT name, (select group_concat(tire_desc) from tires where car.id = tires.car_id), (select group_concat(lights_desc) from lights where car.id = lights.car_id) FROM car Also, if I will use inner selects, will there be any performance issues over joins?

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• Set attribute to all child elements via xsl:choose

  - by Camal

  Hi, assuming I got following XML file : <?xml version="1.0" encoding="ISO-8859-1" ?> <MyCarShop> <Car gender="Boy"> <Door>Lamborghini</Door> <Key>Skull</Key> </Car> <Car gender="Girl"> <Door>Normal</Door> <Key>Princess</Key> </Car> </MyCarShop> I want to perform a transformation so the xml looks like this : <?xml version="1.0" encoding="ISO-8859-1" ?> <MyCarShop> <Car gender="Boy"> <Door color="blue">Lamborghini</Door> <Key color="blue">Skull</Key> </Car> <Car gender="Girl"> <Door color="red">Normal</Door> <Key color="red">Princess</Key> </Car> </MyCarShop> So I want to add a color attribut to each subelement of Car depending on the gender information. I came up with this XSLT but it doesnt work : <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl" > <xsl:output method="xml" indent="yes"/> <!--<xsl:template match="@* | node()"> <xsl:copy> <xsl:apply-templates select="@* | node()"/> </xsl:copy> </xsl:template>--> <xsl:template match="/"> <xsl:element name="MyCarShop"> <xsl:attribute name="version">1.0</xsl:attribute> <xsl:apply-templates/> </xsl:element> </xsl:template> <xsl:template match="Car"> <xsl:element name="Car"> <xsl:apply-templates/> </xsl:element> </xsl:template> <xsl:template match="Door"> <xsl:element name="Door"> <xsl:attribute name="ViewSideIndicator"> <xsl:choose> <xsl:when test="gender = 'Boy' ">Front</xsl:when> <xsl:when test="gender = 'Girl ">Front</xsl:when> </xsl:choose> </xsl:attribute> </xsl:element> </xsl:template> <xsl:template match="Key"> <xsl:element name="Key"> <xsl:apply-templates/> </xsl:element> </xsl:template> </xsl:stylesheet> Does anybody know what might be wrong ? Thanks again!

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• How to update model in the database, from asp.net MVC2, using Entity Framework?

  - by Eedoh

  Hello. I'm building ASP.NET MVC2 application, and using Entity Framework as ORM. I am having troubles updating object in the database. Every time I try entity.SaveChanges(), EF inserts new line in the table, regardless of do I want update, or insert to be done. I tried attaching (like in this next example) object to entity, but then I got {"An object with a null EntityKey value cannot be attached to an object context."} Here's my simple function for inserts and updates (it's not really about vehicles, but it's simpler to explain like this, although I don't think that this effects answers at all)... public static void InsertOrUpdateCar(this Vehicles entity, Cars car) { if (car.Id == 0 || car.Id == null) { entity.Cars.AddObject(car); } else { entity.Attach(car); } entitet.SaveChanges(); } I even tried using AttachTo("Cars", car), but I got the same exception. Anyone has experience with this?

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• Programmatically specifying Django model attributes

  - by mojbro

  Hi! I would like to add attributes to a Django models programmatically, at run time. For instance, lets say I have a Car model class and want to add one price attribute (database column) per currency, given a list of currencies. What is the best way to do this? I had an approach that I thought would work, but it didn't exactly. This is how I tried doing it, using the car example above: from django.db import models class Car(models.Model): name = models.CharField(max_length=50) currencies = ['EUR', 'USD'] for currency in currencies: Car.add_to_class('price_%s' % currency.lower(), models.IntegerField()) This does seem to work pretty well at first sight: $ ./manage.py syncdb Creating table shop_car $ ./manage.py dbshell shop=# \d shop_car Table "public.shop_car" Column | Type | Modifiers -----------+-----------------------+------------------------------------------------------- id | integer | not null default nextval('shop_car_id_seq'::regclass) name | character varying(50) | not null price_eur | integer | not null price_usd | integer | not null Indexes: "shop_car_pkey" PRIMARY KEY, btree (id) But when I try to create a new Car, it doesn't really work anymore: >>> from shop.models import Car >>> mycar = Car(name='VW Jetta', price_eur=100, price_usd=130) >>> mycar <Car: Car object> >>> mycar.save() Traceback (most recent call last): File "<console>", line 1, in <module> File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/db/models/base.py", line 410, in save self.save_base(force_insert=force_insert, force_update=force_update) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/db/models/base.py", line 495, in save_base result = manager._insert(values, return_id=update_pk) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/db/models/manager.py", line 177, in _insert return insert_query(self.model, values, **kwargs) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/db/models/query.py", line 1087, in insert_query return query.execute_sql(return_id) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/db/models/sql/subqueries.py", line 320, in execute_sql cursor = super(InsertQuery, self).execute_sql(None) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/db/models/sql/query.py", line 2369, in execute_sql cursor.execute(sql, params) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/db/backends/util.py", line 19, in execute return self.cursor.execute(sql, params) ProgrammingError: column "price_eur" specified more than once LINE 1: ...NTO "shop_car" ("name", "price_eur", "price_usd", "price_eur... ^

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• How to use Private Inheritence aka C++ in C# and Why not it is present in C#

  - by Vijay

  I know that private inheritance is supported in C++ and only public inheritance is supported in C#. I also came across an article which says that private inheritance usually defines a HAS-A relationship and kind of an aggregation relationship between the classes. EDIT: C++ code for private inheritance: The "Car has-a Engine" relationship can also be expressed using private inheritance: class Car : private Engine { // Car has-a Engine public: Car() : Engine(8) { } // Initializes this Car with 8 cylinders using Engine::start; // Start this Car by starting its Engine }; Now, Is there a way to create a HAS-A relationship between C# classes which is one of the thing that I would like to know - HOW? Another curious question is why doesn't C# support the private (and also protected) inheritance ? - Is not supporting multiple implementation inheritance a valid reason or any other? Is private (and protected) inheritance planned for future versions of C#? Will supporting the private (and protected) inheritance in C# make it a better and widely used language?

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• Rush Hour - Solving the game

  - by Rubys

  Rush Hour if you're not familiar with it, the game consists of a collection of cars of varying sizes, set either horizontally or vertically, on a NxM grid that has a single exit. Each car can move forward/backward in the directions it's set in, as long as another car is not blocking it. You can never change the direction of a car. There is one special car, usually it's the red one. It's set in the same row that the exit is in, and the objective of the game is to find a series of moves (a move - moving a car N steps back or forward) that will allow the red car to drive out of the maze. I've been trying to think how to solve this problem computationally, and I can really not think of any good solution. I came up with a few: Backtracking. This is pretty simple - Recursion and some more recursion until you find the answer. However, each car can be moved a few different ways, and in each game state a few cars can be moved, and the resulting game tree will be HUGE. Some sort of constraint algorithm that will take into account what needs to be moved, and work recursively somehow. This is a very rough idea, but it is an idea. Graphs? Model the game states as a graph and apply some sort of variation on a coloring algorithm, to resolve dependencies? Again, this is a very rough idea. A friend suggested genetic algorithms. This is sort of possible but not easily. I can't think of a good way to make an evaluation function, and without that we've got nothing. So the question is - How to create a program that takes a grid and the vehicle layout, and outputs a series of steps needed to get the red car out? Sub-issues: Finding some solution. Finding an optimal solution (minimal number of moves) Evaluating how good a current state is Example: How can you move the cars in this setting, so that the red car can "exit" the maze through the exit on the right?

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• Django : proper way to use model, duplicates!

  - by llazzaro

  Hello, I have a question about the proper, best way to manage the model. I am relative newbie to django, so I think I need to read more docs, tutorials,etc (suggestions for this would be cool!). Anyway, this is my question : I have a python web crawler, that is "connected" with django model. Crawling is done once a day, so its really common to find "duplicates". To avoid duplicates I do this : cars = Car.Objects.filter(name=crawledItem['name']) if len(cars) 0: #object already exists, update it car = cars[0] else: car = Car() #some non-relevant code here car.save() I want to know, if this is the proper/correct way to do it or its any "automatic" way to do it. Its possible to put the logic inside the Car() constructor also, should I do that? Thanks a lot!

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• Django: many-to-one fields and data integrity

  - by John

  Let's say that I have a Person who runs an inventory system. Each Person has some Cars, and each Car has a very large number of Parts (thousands, let's say). A Person, Bob, uses a Django form to create a Car. Now, Bob goes to create some Parts. It is only at the form level that Django knows that the Parts belong to some specific Car, and that the Parts.ForeignKey(Car) field should only have a specific Car as a choice. When creating a Part, you have to mess with the form's constructor or similar in order to limit the choice of Cars to only the cars owned by Bob. It does not seem proper that to enforce this ownership at the form level. It seems that other users' Cars must be inaccessible to anyone but the owner of the Car. What do you all think about this, and is there any way to enforce this?

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• Iphone -- init method of an abstract class

  - by William Jockusch

  I want to create classes Car, Vehicle, and Airplane with the following properties: Car and Airplane are both subclasses of Vehicle. Car and Airplane both have an initWithString method. The acceptable input strings for Car's and Airplane's initWithString methods do not overlap. Vehicle is "almost abstract", in the sense that any initialized instance should be either a Car or an Airplane. It is possible to pass a string into Vehicle and get back an instance of Car, an instance of Airplane, or nil, depending on the input string. Any particular design pattern I should prefer? In particular for Vehicle's initWithString and/or newVehicleWithString methods.

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• How to optimize this code

  - by phenevo

  Hi I class Car it has a property: string Code and 10 other. common codes is list of strings(string[] ) cars a list of cars(Car[]) filteredListOfCars is List. for (int index = 0; index < cars.Length; index++) { Car car = cars[index]; if (commonCodes.Contains(car.Code)) { filteredListOfCars.Add(car); } } Unfortunately this piece of methodexecutes too long. I have about 50k records How can I lower execution time??

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• Foreach over a collection of IEnumerables

  - by sdr

  I have 3 IEnumerables that I want to iterate over. I want to do something like this: IEnumerable<Car> redCars = GetRedCars(); IEnumerable<Car> greenCars = GetGreenCars(); IEnumerable<Car> blueCars = GetBlueCars(); foreach(Car c in (redCars + greenCars + blueCars)) { c.DoSomething(); } ... The best way I can think of is: ... List<Car> allCars = new List(); allCars.AddRange(redCars); allCars.AddRange(greenCars); allCars.AddRange(blueCars); foreach(car in allCars) { ... } ... Is there a more concise way to do this? Seems like combinding IEnumberables should be trivial.

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• how to design this relation in a DB schema

  - by raticulin

  I have a table Car in my db, one of the columns is purchaseDate. I want to be able to tag every car with a number of Policies (limited to 10 policies). Each policy has a time to life (ttl, a duration of time, like '5 years', '10 months' etc), that is, for how long since the car's purchaseDate the policy can be applied. I need to perform the following actions: when inserting a Car, it will be set with a number of Policies (at least one is set) sometimes a Car will be updated to add/remove a Policy searches must be done taking into account date/policies, for example: 'select all cars that are not covered by any policy as of today' My current design is (pol0..pol9 are the policies): CREATE TABLE Car ( id int NOT NULL IDENTITY(1,1), purchaseDate datetime NOT NULL, //more stuff... pol0 smallint default NULL, pol1 smallint default NULL, pol2 smallint default NULL, pol3 smallint default NULL, pol4 smallint default NULL, pol5 smallint default NULL, pol6 smallint default NULL, pol7 smallint default NULL, pol8 smallint default NULL, pol9 smallint default NULL, PRIMARY KEY (id) ) CREATE TABLE Policy ( id smallint NOT NULL, name varchar(50) collate Latin1_General_BIN NOT NULL, ttl varchar(100) collate Latin1_General_BIN NOT NULL, PRIMARY KEY (id) ) The problem I am facing is that the sql to perform the query above is a nightmare to write. As I don't know in which column each policy can be, so I have to check all columns for every policy etc etc. So I am wondering wether it is worth changing this. My questions are: The smallint as Policy id was chosen instead of an 'int IDENTITY' in order to save some space as there are going to be millions of Car records. It just adds complexity when creating a Policy as we must handle the id etc. Was it worth doing this? I am thinking that maybe there is a much better design? Obviously we could move the policy/car relation to its own table CarPolicy, benefits would be: no limit on 10 policies per car adding/removing etc much easier when only the default policy is applied (when no others are applied one called Default policy is applied), we could signal that by not having any entry in CarPolicy, now this is just done inserting the Default policy id in one of the columns. The cons are that we would need to change the DB, ORM classes etc. What would you recommend? Maybe there is another smart way to implement this that we are not aware without using the CarPolicy table?

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• DataGridView avoiding adding new columns

  - by phenevo

  Why, this code create 2 the same columns in grid (Color and Color). How to inputs data color from collection in column which existing before set datasource ?? public Form1() { InitializeComponent(); DataGridViewTextBoxColumn ds = new DataGridViewTextBoxColumn(); ds.Name = "Color"; dataGridView1.Columns.Add(ds); List<Car> cars=new List<Car>(); for (int i = 0; i < 5; i++) { Car car=new Car {Type = "type" + i.ToString(),Color=Color.Silver}; cars.Add(car); } dataGridView1.DataSource = cars; }

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• update_attributes with validations

  - by Timothy

  I have the following contrived example in Rails. I want to make sure the Garage model has at least one car with this. class Garage has_many :cars validate :at_least_one_car def at_least_one_car if cars.count == 0 errors.add_to_base("needs at least one car") end end end class Car belongs_to :garage end In my form I have a remove button that will set the hidden field _delete to true for an existing car. Let's say there is only one car object and I "delete" it in my form, if I do garage_object.update_attributes(params[:garage]), it will delete the car model and make the garage object invalid. Is there to a way to make it not update the attributes if it will make the model invalid?

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• MySQL UPDATE WHERE IN for each listed value separately?

  - by Tom

  Hi, I've got the following type of SQL: UPDATE photo AS f LEFT JOIN car AS c ON f.car_id=c.car_id SET f.photo_status=1 , c.photo_count=c.photo_count+1 WHERE f.photo_id IN ($ids) Basically, two tables (car & photo) are related. The list in $ids contains unique photo ids, such as (34, 87, 98, 12). With the query, I'm setting the status of each photo in that list to "1" in the photo table and simultaneously incrementing the photo count in the car table for the car at hand. It works but there's one snag: Because the list can contain multiple photo ids that relate to the same car, the photo count only ever gets incremented once. If the list had 10 photos associated with the same car, photo_count would become 1 .... whereas I'd like to increment it to 10. Is there a way to make the incrementation occur for each photo individually through the join, as opposed to MySQL overthinking it for me? I hope the above makes sense. Thanks.

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• NetLogo 4.1 - implementation of a motorway ( Problem creating collision of cars )

  - by user206019

  Hi there, I am trying to create a simulation of motorway and the behaviour of the drivers in NetLogo. I have some questions that I m struggling to solve. Here is my code: globals [ selected-car ;; the currently selected car average-speed ;; average speed of all the cars look-ahead ] turtles-own [ speed ;; the current speed of the car speed-limit ;; the maximum speed of the car (different for all cars) lane ;; the current lane of the car target-lane ;; the desired lane of the car change? ;; true if the car wants to change lanes patience ;; the driver's current patience max-patience ;; the driver's maximum patience ] to setup ca import-drawing "my_road3.png" set-default-shape turtles "car" crt number_of_cars [ setup-cars ] end to setup-cars set color blue set size .9 set lane (random 3) set target-lane (lane + 1) setxy round random-xcor (lane + 1) set heading 90 set speed 0.1 + random 9.9 set speed-limit (((random 11) / 10) + 1) set change? false set max-patience ((random 50) + 10) set patience (max-patience - (random 10)) ;; make sure no two cars are on the same patch loop [ ifelse any? other turtles-here [ fd 1 ] [ stop ] ;if count turtles-here > 1 ; fd 0.1 ;if ; ;ifelse (any? turtles-on neighbors) or (count turtles-here > 1) ;[ ; ifelse (count turtles-here = 1) ; [ if any? turtles-on neighbors ; [ ; if distance min-one-of turtles-on neighbors [distance myself] > 0.9 ; [stop] ; ] ; ] ; [ fd 0.1 ] ;] ;[ stop ] ] end to go drive end to drive ;; first determine average speed of the cars set average-speed ((sum [speed] of turtles) / number_of_cars) ;set-current-plot "Car Speeds" ;set-current-plot-pen "average" ;plot average-speed ;set-current-plot-pen "max" ;plot (max [speed] of turtles) ;set-current-plot-pen "min" ;plot (abs (min [speed] of turtles) ) ;set-current-plot-pen "selected-car" ;plot ([speed] of selected-car) ask turtles [ ifelse (any? turtles-at 1 0) [ set speed ([speed] of (one-of (turtles-at 1 0))) decelerate ] [ ifelse (look-ahead = 2) [ ifelse (any? turtles-at 2 0) [ set speed ([speed] of (one-of turtles-at 2 0)) decelerate ] [ accelerate if count turtles-at 0 1 = 0 and ycor < 2.5 [lt 90 fd 1 rt 90] ] ] [accelerate if count turtles-at 0 1 = 0 and ycor < 2.5 [lt 90 fd 1 rt 90] ] ] if (speed < 0.01) [ set speed 0.01 ] if (speed > speed-limit) [ set speed speed-limit ] ifelse (change? = false) [ signal ] [ change-lanes ] ;; Control for making sure no one crashes. ifelse (any? turtles-at 1 0) and (xcor != min-pxcor - .5) [ set speed [speed] of (one-of turtles-at 1 0) ] [ ifelse ((any? turtles-at 2 0) and (speed > 1.0)) [ set speed ([speed] of (one-of turtles-at 2 0)) fd 1 ] [jump speed] ] ] tick end ;; increase speed of cars to accelerate ;; turtle procedure set speed (speed + (speed-up / 1000)) end ;; reduce speed of cars to decelerate ;; turtle procedure set speed (speed - (slow-down / 1000)) end to signal ifelse (any? turtles-at 1 0) [ if ([speed] of (one-of (turtles-at 1 0))) < (speed) [ set change? true ] ] [ set change? false ] end ;; undergoes search algorithms to change-lanes ;; turtle procedure show ycor ifelse (patience <= 0) [ ifelse (max-patience <= 1) [ set max-patience (random 10) + 1 ] [ set max-patience (max-patience - (random 5)) ] set patience max-patience ifelse (target-lane = 0) [ set target-lane 1 set lane 0 ] [ set target-lane 0 set lane 1 ] ] [ set patience (patience - 1) ] ifelse (target-lane = lane) [ ifelse (target-lane = 0) [ set target-lane 1 set change? false ] [ set target-lane 0 set change? false ] ] [ ifelse (target-lane = 1) [ ifelse (pycor = 2) [ set lane 1 set change? false ] [ ifelse (not any? turtles-at 0 1) [ set ycor (ycor + 1) ] [ ifelse (not any? turtles-at 1 0) [ set xcor (xcor + 1) ] [ decelerate if (speed <= 0) [ set speed 0.1 ] ] ] ] ] [ ifelse (pycor = -2) [ set lane 0 set change? false ] [ ifelse (not any? turtles-at 0 -1) [ set ycor (ycor - 1) ] [ ifelse (not any? turtles-at 1 0) [ set xcor (xcor + 1) ] [ decelerate if (speed <= 0) [ set speed 0.1 ] ] ] ] ] ] end I know its a bit messy because I am using code from other models from the library. I want to know how to create the collision of the cars. I can't think of any idea. As you notice my agent has almost the same size as the patch (I set it to 0.9 so that you can distinguish the space between 2 cars when they are set next to each other and I round the coordinates so that they are set to the centre of the patch). In my accelerate procedure I set my agent to turn left, move 1, turn right in a loop. I want to know if there's a command that lets me make the agent jump from one lane to the other (to the patch next to it on its left) without making it turn and move. And last, if you notice the code i created the car checks the patch that is next to it on the lane on its left and the patch in front of it and the back of it. So if the 3 patches on its left are empty then it can change lane. The fuzzy part is that when i run the setup and I press Go sometimes (not always) the car goes out of the 3 basic lanes. To understand this I have 7 lanes. The middle one which I don't use which is lane 0. Then there are 3 lanes on top of lane 0 and 3 below it. So the code I am using refers to the upper 3 lanes where I set the cars but for some reason some of the cars change lane and go to lane -3 then -2 and so forth. If someone can give me a tip I would really appreciate it. Thank you in advance. Tip: if you want to try this code in netlogo keep in mind that on interface tab I have 2 buttons one setup and one go as well as 3 sliders with names: number_of_cars , speed-up , slow-down.

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• How does the government plan to find all nasty bugs in car software?

  - by Hamish Grubijan

  They are confident that they can make "drive-by-wire" cars safer. What can our QA department learn from the government? Thanks.

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• Finding the normals of an oriented bounding box?

  - by Milo

  Here is my problem. I'm working on the physics for my 2D game. All objects are oriented bounding boxes (OBB) based on the separate axis theorem. In order to do collision resolution, I need to be able to get an object out out of the object it is penetrating. To do this I need to find the normal of the face(s) that the other OBB is touching. Example: The small red OBB is a car lets say, and the big OBB is a static building. I need to determine the unit vector that is the normal of the building edge(s) the car is penetrating to get the car out of there. Here are my questions: How do I determine which edges the car is penetrating. I know how to determine the normal of an edge, but how do I know if I need (-dy, dx) or (dy, -dx)? In the case I'm demonstrating the car is penetrating 2 edges, which edge(s) do I use to get it out? Answers or help with any or all of these is greatly appreciated. Thank you

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