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• ViewModel updates after Model server roundtrip

  - by Pavel Savara

  I have stateless services and anemic domain objects on server side. Model between server and client is POCO DTO. The client should become MVVM. The model could be graph of about 100 instances of 20 different classes. The client editor contains diverse tab-pages all of them live-connected to model/viewmodel. My problem is how to propagate changes after server round-trip nice way. It's quite easy to propagate changes from ViewModel to DTO. For way back it would be possible to throw away old DTO and replace it whole with new one, but it will cause lot of redrawing for lists/DataTemplates. I could gather the server side changes and transmit them to client side. But the names of fields changed would be domain/DTO specific, not ViewModel specific. And the mapping seems nontrivial to me. If I should do it imperative way after round-trip, it would break SOC/modularity of viewModels. I'm thinking about some kind of mapping rule engine, something like automappper or emit mapper. But it solves just very plain use-cases. I don't see how it would map/propagate/convert adding items to list or removal. How to identify instances in collections so it could merge values to existing instances. As well it should propagate validation/error info. Maybe I should implement INotifyPropertyChanged on DTO and try to replay server side events on it ? And then bind ViewModel to it ? Would binding solve the problems with collection merges nice way ? Is EventAgregator from PRISM useful for that ? Is there any event record-replay component ? Is there better client side pattern for architecture with server side logic ?

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• Why use SQL database?

  - by martinthenext

  I'm not quite sure stackoverflow is a place for such a general question, but let's give it a try. Being exposed to the need of storing application data somewhere, I've always used MySQL or sqlite, just because it's always done like that. As it seems like the whole world is using these databases, most of all software products, frameworks, etc. It is rather hard for a beginning developer like me to ask a question - why? Ok, say we have some object-oriented logic in our application, and objects are related to each other somehow. We need to map this logic to the storage logic, so we need relations between database objects too. This leads us to using relational database and I'm ok with that - to put it simple, our database rows sometimes will need to have references to other tables' rows. But why do use SQL language for interaction with such a database? SQL query is a text message. I can understand this is cool for actually understanding what it does, but isn't it silly to use text table and column names for a part of application that no one ever seen after deploynment? If you had to write a data storage from scratch, you would have never used this kind of solution. Personally, I would have used some 'compiled db query' bytecode, that would be assembled once inside a client application and passed to the database. And it surely would name tables and colons by id numbers, not ascii-strings. In the case of changes in table structure those byte queries could be recompiled according to new db schema, stored in XML or something like that. What are the problems of my idea? Is there any reason for me not to write it myself and to use SQL database instead?

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• Binary search in a sorted (memory-mapped ?) file in Java

  - by sds

  I am struggling to port a Perl program to Java, and learning Java as I go. A central component of the original program is a Perl module that does string prefix lookups in a +500 GB sorted text file using binary search (essentially, "seek" to a byte offset in the middle of the file, backtrack to nearest newline, compare line prefix with the search string, "seek" to half/double that byte offset, repeat until found...) I have experimented with several database solutions but found that nothing beats this in sheer lookup speed with data sets of this size. Do you know of any existing Java library that implements such functionality? Failing that, could you point me to some idiomatic example code that does random access reads in text files? Alternatively, I am not familiar with the new (?) Java I/O libraries but would it be an option to memory-map the 500 GB text file (I'm on a 64-bit machine with memory to spare) and do binary search on the memory-mapped byte array? I would be very interested to hear any experiences you have to share about this and similar problems.

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• get lattitude and longitude of a place against its zipcode

  - by yunas

  Hello i have used the following code to get the location of the particular place on map using the following piece of code NSString * urlString = [[NSString alloc] initWithFormat:@"http://maps.google.com/maps/geo?key=%@&output=xml&q=%@",GoogleMapsAPIKey,[placeName stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]; result: <?xml version="1.0" encoding="UTF-8" ?> <kml xmlns="http://earth.google.com/kml/2.0"><Response> <name>postdam</name> <Status> <code>200</code> <request>geocode</request> </Status> <Placemark id="p1"> <address>Potsdam, Germany</address> <AddressDetails Accuracy="4" xmlns="urn:oasis:names:tc:ciq:xsdschema:xAL:2.0"><Country><CountryNameCode>DE</CountryNameCode><CountryName>Deutschland</CountryName><AdministrativeArea><AdministrativeAreaName>Brandenburg</AdministrativeAreaName><SubAdministrativeArea><SubAdministrativeAreaName>Potsdam</SubAdministrativeAreaName><Locality><LocalityName>Potsdam</LocalityName></Locality></SubAdministrativeArea></AdministrativeArea></Country></AddressDetails> <ExtendedData> <LatLonBox north="52.4513968" south="52.3424614" east="13.1866602" west="12.9305414" /> </ExtendedData> <Point><coordinates>13.0586008,52.3969627,0</coordinates></Point> </Placemark> </Response></kml> but now i want to get the information agianst the zipcode how to do that using the maps.google.com ???

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• video calling (center)

  - by rrejc

  We are starting to develop a new application and I'm searching for information/tips/guides on application architecture. Application should: read the data from an external (USB) device send the data to the remote server (through internet) receive the data from the remote server perform a video call with to the calling (support) center receive a video call call from the calling (support) center support touch screens In addition: some of the data should also be visible through the web page. So I was thinking about: On the server side: use the database (probably MS SQL) use ORM (nHibernate) to map the data from the DB to the domain objects create a layer with business logic in C# create a web (WCF) services (for client application) create an asp.net mvc application (for item 7.) to enable data view through the browser On the client side I would use WPF 4 application which will communicate with external device and the wcf services on the server. So far so good. Now the problem begins. I have no idea how to create a video call (outgoing or incoming) part of the application. I believe that there is no problem to communicate with microphone, speaker, camera with WPF/C#. But how to communicate with the call center? What protocol and encoding should be used? I think that I will need to create some kind of server which will: have a list of operators in the calling center and track which operator is occupied and which operator is free have a list of connected end users receive incoming calls from end users and delegate call to free operator delegate calls from calling center to the end user Any info, link, anything on where to start would be much appreciated. Many thanks!

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• remove text in parentheses and the parentheses using .filter() or .slice()

  - by liz

  i have a table with code like this: <tr> <th scope="row">5-17</th> <td>23.6 (22.0-24.0)</td> <td>18.0 (17-20.0)</td> </tr> <tr> <th scope="row">Total 0-17</th> <td>20.6 (8-15.6)</td> <td>16.1 (22.2-24.0)</td> </tr> i am using the following function to find the contents of the table cells and bring it into an array: var l1 = $('#datatable td:nth-child(2)').map(function() { return $(this).text(); }).get(); the table fragment's id is "datatable". this returns properly, however i am putting this array into jqPlot and it cant read the stuff between the parentheses or the parentheses themselves. i need the data to remain in the table however because we are displaying both the table and the chart. i cant reformat (add spans around the content i want to remove etc) because these tables are being generated by another piece of software. i think what i need to do is either slice off after the space or use a regex to find and remove. not sure how to proceed with either of these. thanks!

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• Add new types to Go

  - by nevalu

  I'm trying add new types for that been managed/used as in Go core types. To create new types is anything very interesting to validate data before of send it to a non-SQL DBMS or to check data from a form. Go uses univeral constants to define them at global level: var DateType = universe.DefineType("date", universePos, &dateType{}) In this case they're defined to be called from a package like types: var Date = &dateType{} I get these errors: test.go:58: o.lit undefined (cannot refer to unexported field lit) test.go:62: *dateType is not Type missing Pos() token.Position The code is based on: http://github.com/tav/go/blob/master/src/pkg/exp/eval/value.go http://github.com/tav/go/blob/master/src/pkg/exp/eval/type.go package main import ( "exp/eval" "fmt" // "go/token" ) // http://github.com/tav/go/blob/master/src/pkg/exp/eval/value.go type DateValue interface { eval.Value Get(*eval.Thread) string Set(*eval.Thread, string) } /* Date */ type dateV string func (v *dateV) String() string { return fmt.Sprint(*v) } func (v *dateV) Assign(t *eval.Thread, o eval.Value) { *v = dateV(o.(DateValue).Get(t)) } func (v *dateV) Get(*eval.Thread) string { return string(*v) } func (v *dateV) Set(t *eval.Thread, x string) { *v = dateV(x) } // http://github.com/tav/go/blob/master/src/pkg/exp/eval/type.go type Type interface { eval.Type // isDate returns true if this is a date type. isDate() bool } /* Common type */ type commonType struct{} // added func (commonType) isDate() bool { return false } /* Date */ type dateType struct { commonType } // * It should not be an universal constant //var universePos = token.Position{"<universe>", 0, 0, 0} // added //var DateType = universe.DefineType("date", universePos, &dateType{}) var Date = &dateType{} func (t *dateType) compat(o Type, conv bool) bool { t2, ok := o.lit().(*dateType) return ok && t == t2 } func (t *dateType) lit() Type { return t } func (t *dateType) isDate() bool { return true } func (t *dateType) String() string { return "<date>" } func (t *dateType) Zero() eval.Value { res := dateV("") return &res } /* Named types */ /* type NamedType struct { eval.NamedType Def Type }*/ type NamedType struct { // added // token.Position Name string // Underlying type. If incomplete is true, this will be nil. // If incomplete is false and this is still nil, then this is // a placeholder type representing an error. Def Type // True while this type is being defined. incomplete bool methods map[string]eval.Method } func (t *NamedType) isDate() bool { return t.Def.isDate() } /* *********************** */ func main() { print("foo") }

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• Which PHP library I should choose to work with CouchDB?

  - by Guss

  I want to try playing with CouchDB for a new project I'm writing (as a hobby, not part of my job). I'm well versed in PHP, but I haven't programmed with CouchDB at all, and also I have little experience with non-SQL databases. From looking at CouchDB's "Getting Started with PHP" document they recommend using a third-party library or writing your own client using their RESTful HTTP API. I think I'd rather not mess with writing protocol implementations myself at this point, but what is your experience with writing PHP to work with CouchDB? I haven't tested any of the alternatives yet, but I looked at: PHPillow : I'm interested in the way they implement ORM. I wasn't planning to do ORM, but my problem domain probably map well to that method. PHP Object Freezer: seems like a poor man's ORM - I can use it to implement an actual ORM, or just as an easy store/retrieve document API but it seems too primitive. PHP-on-Couch : Also a bit simple, but they have an interesting API for views and from the documentation it looks usable enough. PHP CouchDB Extension : From the listed options this looks like it has the best chance of making it into the PHP mainline itself, and also has the most complete API. Any opinion one wish to share on each library is welcome.

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• Mapping self-table one-to-many using non-PK clolumns

  - by Harel Moshe

  Hey, i have a legacy DB to which a Person object is mapped, having a collection of family-members, like this: class Person { ... string Id; /* 9-digits string */ IList<Person> Family; ... } The PERSON table seems like: Id: CHAR(9), PK FamilyId: INT, NOT NULL and several other non-relevant columns. I'm trying to map the Family collection to the PERSON table using the FamilyId column, which is not the PK as mentioned above. So, i actually have a one-to-many which is self-table-referential. I'm getting an error saying 'Cast is not valid' when my mapping looks like this: ... <set name="Family" table="Person" lazy="false"> <key column="FamilyId" /> <one-to-many class="Person" /> </set> ... because obviously, the join NHibernate is trying to make is between the PK column, Id, and the 'secondary' column, FamilyId, instead of joining the FamilyId column to itself. Any ideas please?

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• iphone mkmapview

  - by karthik

  Hi, This is karthik. I am developing an app using mapview in iphone. I have to use two different pins to show user locations. That two users are different type . One user is belong to some category and another one is some other category. I have to check that category and want to plot pin depend upon that category. When I try to do that, that pin is not showing properly. For a certain category it shows another pin, not what i set there. Can anyone help me? What i need is i want to load two different pins in map depend upon some category. For example , if that category is shopping mall then i have to show building image then if there is any garden i have to show some other image at a same time not one by one . I want to plot two pins with different category at the same time. For that,what could i do? I tried lot of solution , but its not showing properly. Help me?

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• AutoMapper and flattening nested arrays

  - by Bryan Slatner

  I'm trying to use AutoMapper to flatten multiple levels of arrays. Consider the following source classes: class X { public string A { get; set; } public Y[] B { get; set; } } class Y { public string C { get; set; } public Z[] D { get; set; } } class Z { public string E { get; set; } public string F { get; set; } } And the following destination: class Destination { public string A { get; set; } public string C { get; set; } public string E { get; set; } public string F { get; set; } } What I'd like to be able to do is get a List from one or more X, e.g.: Mapper.Map<IEnumerable<X>, IEnumerable<Destination>>(arrayOfX); I'm unable to figure out what sort of mapping configuration to use to achieve this. MapFrom seems like the way to go for 1:1 compositions, but doesn't seem to be able to handle the array (or other enumerable) unless I use AutoMapper's destination naming convention. Any insights on how to achieve this?

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• Building a many-to-many db schema using only an unpredictable number of foreign keys

  - by user1449855

  Good afternoon (at least around here), I have a many-to-many relationship schema that I'm having trouble building. The main problem is that I'm only working with primary and foreign keys (no varchars or enums to simplify things) and the number of many-to-many relationships is not predictable and can increase at any time. I looked around at various questions and couldn't find something that directly addressed this issue. I split the problem in half, so I now have two one-to-many schemas. One is solved but the other is giving me fits. Let's assume table FOO is a standard, boring table that has a simple primary key. It's the one in the one-to-many relationship. Table BAR can relate to multiple keys of FOO. The number of related keys is not known beforehand. An example: From a query FOO returns ids 3, 4, 5. BAR needs a unique key that relates to 3, 4, 5 (though there could be any number of ids returned) The usual join table does not work: Table FOO_BAR primary_key | foo_id | bar_id | Since FOO returns 3 unique keys and here bar_id has a one-to-one relationship with foo_id. Having two join tables does not seem to work either, as it still can't map foo_ids 3, 4, 5 to a single bar_id. Table FOO_TO_BAR primary_key | foo_id | bar_to_foo_id | Table BAR_TO_FOO primary_key | foo_to_bar_id | bar_id | What am I doing wrong? Am I making things more complicated than they are? How should I approach the problem? Thanks a lot for the help.

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• jquery filter .not()

  - by FFish

  I have a form with image thumbnails to select with checkboxes for downloading. I want an array with the images in jQuery for an Ajax call. 2 questions: - On the top of the table there is a checkbox to toggle all checkboxes that I want to exclude from the mapping. I had a look at jQuery's .not() but I can't implement it with the :checkbox selector - is the following example code correct? $(document).ready(function() { $('#myform').submit(function() { var images = $("input:checkbox", this).map(function() { return $(this).attr("name"); }).get().join(); alert(products); // outputs: ",check1,check2,check3" return false; // cancel submit action by returning false }); }); // end doc ready HTML: <form id="myform" action="" > <input type="checkbox" id="toggleCheck" onclick="toggleSelectAll()" checked="checked" ><br /> <input type="checkbox" name="001.jpg" checked="checked" /><br /> <input type="checkbox" name="002.jpg" checked="checked" /><br /> <input type="checkbox" name="003.jpg" checked="checked" /><br /> <br /> <input type="submit" value="download" > </form>

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• Google Maps: openInfoWindowTabsHtml + GDownloadUrl (Ajax call) question

  - by Spiros

  I am facing the following problem. On an Google Map I want to add info windows with tabs, where content is loaded from an external file using the GDownloadUrl method. The code works about fine, but with two problems. a) The first time I click on a marker, nothing hapens. I need to click twice to get an info box. After that it works ok. b) When I close an info box and open it again, the tabs repeat themselves. Every time I reopen the info box, those tabs get repeated. So, if using the code below and open the info box 3 times, I get 6 tabs (Info, Photos, Info, Photos, Info, Photos). Any idea of what I am doing wrong here? I have also tried this with JQuery's $.get method, but the results are exactly the same. function createREMarker(lat,long,reID) { var reMarker = new GMarker(rePoint,iconRE); GEvent.addListener(reMarker, "click", function() { GDownloadUrl('testcontent.php?reID='+reID+'&what=info', function(data) { content1 = data; }); GDownloadUrl('testcontent.php?reID='+reID+'&what=photos', function(data) { content2 = data; }); tabs.push(new GInfoWindowTab('Info', '<div id="mapOverlayContent" style="width:375px; height:220px; overflow:auto;">'+content1+'</div>')); tabs.push(new GInfoWindowTab('Photos', '<div id="mapOverlayContent" style="width:375px; height:220px; overflow:auto;">'+content2+'</div>')); reMarker.openInfoWindowTabsHtml(tabs); }); return reMarker; };

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• JPA - Performance with using multiple entity manager

  - by Nguyen Tuan Linh

  My situation is: The code is not mine I have two kinds of database: one is Dad, one is Son. In Dad, I have a table to store JNDI name. I will look up Dad using JNDI, create entity manager, and retrieve this table. From these retrieved JNDI names, I will create multiple entity managers using multiple Son databases. The problem is: Son have thousands of entities. It takes each Son database around 10 minutes to load all entities. If there is 4 Son databases, it will be 40 minutes. My question: Is there any way to load all entities and use them for all entity manager? Please look at the code below For each Son JNDI: Map<String, String> puSonProperties = new HashMap<String, String>(); puSonProperties.put("javax.persistence.jtaDataSource", sonJndi); EntityManagerFactory emf = Persistence.createEntityManagerFactory("PUSon", puSonProperties); PUSon - All of them use the same persistence unit log.info("Verify entity manager for son: {0} - {1}", sonCode, emSon.find(Son_configuration.class, 0) != null ? "ok" : "failed!"); This is the actual code where the loading of all entities begins. 10 mins.

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• EF4 and multiple abstract levels

  - by Cedric

  I need to use inheritance with EF4 and the TPH model created from DB. I created a new projet to test simples classes. There is my class model: There is my table in SQL SERVER 2008 : VEHICLE ID : int PK Owner : varchar(50) Consumption : float FirstCirculationDate : date Type : varchar(50) Discriminator : varchar(10) I added a condition in my EDMX on the Discriminator field to differentiate the Scooter, Car, Motorbike and Bike entities. MotorizedVehicle and Vehicle are Abstract. But when I compile, this error appears : Error 3032: Problem in mapping fragments starting at lines 78, 85:EntityTypes EF4InheritanceModel.Scooter, EF4InheritanceModel.Motorbike, EF4InheritanceModel.Car, EF4InheritanceModel.Bike are being mapped to the same rows in table Vehicle. Mapping conditions can be used to distinguish the rows that these types are mapped to. Edit : To Ladislav : I try it and error change to become it for all of my entities : Error 3034: Problem in mapping fragments starting at lines 72, 86:An entity is mapped to different rows within the same table. Ensure these two mapping fragments do not map two groups of entities with overlapping keys to two distinct groups of rows. To Henk (with Ladislay suggestion) : There are all of mappings details : What's wrong ? Thanks

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• simple Java "service provider frameworks"?

  - by Jason S

  I refer to "service provider framework" as discussed in Chapter 2 of Effective Java, which seems like exactly the right way to handle a problem I am having, where I need to instantiate one of several classes at runtime, based on a String to select which service, and an Configuration object (essentially an XML snippet): But how do I get the individual service providers (e.g. a bunch of default providers + some custom providers) to register themselves? interface FooAlgorithm { /* methods particular to this class of algorithms */ } interface FooAlgorithmProvider { public FooAlgorithm getAlgorithm(Configuration c); } class FooAlgorithmRegistry { private FooAlgorithmRegistry() {} static private final Map<String, FooAlgorithmProvider> directory = new HashMap<String, FooAlgorithmProvider>(); static public FooAlgorithmProvider getProvider(String name) { return directory.get(serviceName); } static public boolean registerProvider(String name, FooAlgorithmProvider provider) { if (directory.containsKey(name)) return false; directory.put(name, provider); return true; } } e.g. if I write custom classes MyFooAlgorithm and MyFooAlgorithmProvider to implement FooAlgorithm, and I distribute them in a jar, is there any way to get registerProvider to be called automatically, or will my client programs that use the algorithm have to explicitly call FooAlgorithmRegistry.registerProvider() for each class they want to use?

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• What permissions do I need to grant to run RavenDB in Server mode?

  - by dalesmithtx

  I'm reading through Rob Ashton's excellent blog post on RavenDB: http://codeofrob.com/archive/2010/05/09/ravendb-an-introduction.aspx and I'm working through the code as I read. But when I try to add an index, I get a 401 error. Here's the code: class Program { static void Main(string[] args) { using (var documentStore = new DocumentStore() { Url = "http://localhost:8080" }) { documentStore.Initialise(); documentStore.DatabaseCommands.PutIndex( "BasicEntityBySomeData", new IndexDefinition<BasicEntity, BasicEntity>() { Map = docs => from doc in docs where doc.SomeData != null select new { SomeData = doc.SomeData }, }); string entityId; using (var documentSession = documentStore.OpenSession()) { var entity = new BasicEntity() { SomeData = "Hello, World!", SomeOtherData = "This is just another property", }; documentSession.Store(entity); documentSession.SaveChanges(); entityId = entity.Id; var loadedEntity = documentSession.Load<BasicEntity>(entityId); Console.WriteLine(loadedEntity.SomeData); var docs = documentSession.Query<BasicEntity>("BasicEntityBySomeData") .Where("SomeData:Hello~") .WaitForNonStaleResults() .ToArray(); docs.ToList().ForEach(doc => Console.WriteLine(doc.SomeData)); Console.Read(); } } } It throws the 401 error when on the line that makes the PutIndex() call. Any ideas what permissions I need to apply? And where I need to apply them?

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• Deserializing XML to Objects in C#

  - by Justin Bozonier

  So I have xml that looks like this: <todo-list> <id type="integer">#{id}</id> <name>#{name}</name> <description>#{description}</description> <project-id type="integer">#{project_id}</project-id> <milestone-id type="integer">#{milestone_id}</milestone-id> <position type="integer">#{position}</position> <!-- if user can see private lists --> <private type="boolean">#{private}</private> <!-- if the account supports time tracking --> <tracked type="boolean">#{tracked}</tracked> <!-- if todo-items are included in the response --> <todo-items type="array"> <todo-item> ... </todo-item> <todo-item> ... </todo-item> ... </todo-items> </todo-list> How would I go about using .NET's serialization library to deserialize this into C# objects? Currently I'm using reflection and I map between the xml and my objects using the naming conventions.

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• Rot13 for numbers.

  - by dreeves

  EDIT: Now a Major Motion Blog Post at http://messymatters.com/sealedbids The idea of rot13 is to obscure text, for example to prevent spoilers. It's not meant to be cryptographically secure but to simply make sure that only people who are sure they want to read it will read it. I'd like to do something similar for numbers, for an application involving sealed bids. Roughly I want to send someone my number and trust them to pick their own number, uninfluenced by mine, but then they should be able to reveal mine (purely client-side) when they're ready. They should not require further input from me or any third party. (Added: Note the assumption that the recipient is being trusted not to cheat.) It's not as simple as rot13 because certain numbers, like 1 and 2, will recur often enough that you might remember that, say, 34.2 is really 1. Here's what I'm looking for specifically: A function seal() that maps a real number to a real number (or a string). It should not be deterministic -- seal(7) should not map to the same thing every time. But the corresponding function unseal() should be deterministic -- unseal(seal(x)) should equal x for all x. I don't want seal or unseal to call any webservices or even get the system time (because I don't want to assume synchronized clocks). (Added: It's fine to assume that all bids will be less than some maximum, known to everyone, say a million.) Sanity check: > seal(7) 482.2382 # some random-seeming number or string. > seal(7) 71.9217 # a completely different random-seeming number or string. > unseal(seal(7)) 7 # we always recover the original number by unsealing.

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• nhibernate not taking mappings from assembly

  - by cvista

  Hi I'm using fnh and castle nhib facility. I followed the advice from mike hadlow here: http://mikehadlow.blogspot.com/2009/01/integrating-fluent-nhibernate-and.html here is my FluentNHibernateConfigurationBuilder: public Configuration GetConfiguration(IConfiguration facilityConfiguration) { var defaultConfigurationBuilder = new DefaultConfigurationBuilder(); var configuration = defaultConfigurationBuilder.GetConfiguration(facilityConfiguration); configuration.AddMappingsFromAssembly(typeof(User).Assembly); return configuration; } i know the facility is picking it up as i can break inside that method and it steps through. however, when it's done, non of the mappings are created and i get the following error when i try to save an entity: No persister for: IsItGd.Model.Entities.User here is my user class: //simple model of web user public class User { public virtual int Id { get; set; } public virtual string FullName { get; set; } } and here is the mapping: public class UserMap : ClassMap<User> { public UserMap() { Id(x=>x.Id); Map(x=>x.FullName); } } i really can't see what the problem is. the strange thing is - is that if i use automapping it picks everything up - but i don't want to use automapping as i can't do certain things in that scenario. any clues? w://

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• How to find minimum cut-sets for several subgraphs of a graph of degrees 2 to 4

  - by Tore

  I have a problem, Im trying to make A* searches through a grid based game like pacman or sokoban, but i need to find "enclosures". What do i mean by enclosures? subgraphs with as few cut edges as possible given a maximum size and minimum size for number of vertices that act as soft constraints. Alternatively you could say i am looking to find bridges between subgraphs, but its generally the same problem. Given a game that looks like this, what i want to do is find enclosures so that i can properly find entrances to them and thus get a good heuristic for reaching vertices inside these enclosures. So what i want is to find these colored regions on any given map. The reason for me bothering to do this and not just staying content with the performance of a simple manhattan distance heuristic is that an enclosure heuristic can give more optimal results and i would not have to actually do the A* to get some proper distance calculations and also for later adding competitive blocking of opponents within these enclosures when playing sokoban type games. Also the enclosure heuristic can be used for a minimax approach to finding goal vertices more properly. Do you know of a good algorithm for solving this problem or have any suggestions in things i should explore?

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• SQL GUID Vs Integer

  - by Dal

  Hi I have recently started a new job and noticed that all the SQL tables use the GUID data type for the primary key. In my previous job we used integers (Auto-Increment) for the primary key and it was a lot more easier to work with in my opinion. For example, say you had two related tables; Product and ProductType - I could easily cross check the 'ProductTypeID' column of both tables for a particular row to quickly map the data in my head because its easy to store the number (2,4,45 etc) as opposed to (E75B92A3-3299-4407-A913-C5CA196B3CAB). The extra frustration comes from me wanting to understand how the tables are related, sadly there is no Database diagram :( A lot of people say that GUID's are better because you can define the unique identifer in your C# code for example using NewID() without requiring SQL SERVER to do it - this also allows you to know provisionally what the ID will be.... but I've seen that it is possible to still retrieve the 'next auto-incremented integer' too. A DBA contractor reported that our queries could be up to 30% faster if we used the Integer type instead of GUIDS... Why does the GUID data type exist, what advantages does it really provide?... Even if its a choice by some professional there must be some good reasons as to why its implemented?

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• Rails 3 : create two dimensional hash and add values from a loop

  - by John

  I have two models : class Project < ActiveRecord::Base has_many :ticket attr_accessible .... end class Ticket < ActiveRecord::Base belongs_to :project attr_accessible done_date, description, .... end In my ProjectsController I would like to create a two dimensional hash to get in one variable for one project all tickets that are done (with done_date as key and description as value). For example i would like a hash like this : What i'm looking for : @tickets_of_project = ["done_date_1" => ["a", "b", "c"], "done_date_2" => ["d", "e"]] And what i'm currently trying (in ProjectsController) ... def show # Get current project @project = Project.find(params[:id]) # Get all dones tickets for a project, order by done_date @tickets = Ticket.where(:project_id => params[:id]).where("done_date IS NOT NULL").order(:done_date) # Create a new hash @tickets_of_project = Hash.new {} # Make a loop on all tickets, and want to complete my hash @tickets.each do |ticket| # TO DO #HOW TO PUT ticket.value IN "tickets_of_project" WITH KEY = ticket.done_date ??** end end I don't know if i'm in a right way or not (maybe use .map instead of make a where query), but how can I complete and put values in hash by checking index if already exist or not ? Thanx :)

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• Mapping composite foreign keys in a many-many relationship in Entity Framework

  - by Kirk Broadhurst

  I have a Page table and a View table. There is a many-many relationship between these two via a PageView table. Unfortunately all of these tables need to have composite keys (for business reasons). Page has a primary key of (PageCode, Version), View has a primary key of (ViewCode, Version). PageView obviously enough has PageCode, ViewCode, and Version. The FK to Page is (PageCode, Version) and the FK to View is (ViewCode, Version) Makes sense and works, but when I try to map this in Entity framework I get Error 3021: Problem in mapping fragments...: Each of the following columns in table PageView is mapped to multiple conceptual side properties: PageView.Version is mapped to (PageView_Association.View.Version, PageView_Association.Page.Version) So clearly enough, EF is having a complain about the Version column being a common component of the two foreign keys. Obviously I could create a PageVersion and ViewVersion column in the join table, but that kind of defeats the point of the constraint, i.e. the Page and View must have the same Version value. Has anyone encountered this, and is there anything I can do get around it? Thanks!

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