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• Best (functional?) programming language to learn coming from Mathematica

  - by Will Robertson

  As a mechanical engineering PhD student, I haven't had a great pedigree in programming as part of my “day job”. I started out in Matlab (having written some Hypercard and Applescript back in the day, and being introduced to Ada, of all things, in my 1st undergrad year), learned to program—if you can call it that—in (La)TeX; and finally discovered and fell for Mathematica. Now I'm interested in learning a "real" programming language that I can enjoy in the same sort of style as Mathematica, which tries to stress functional programming since it seems to map more nicely to how certain kinds of mathematics can be written algorithmically. So which functional language should I learn? I guess the obvious answer is “as many as possible”, but let's start out humble and give a single, well-considered option a good crack. I've heard good things about, say, Haskell and Scala, but I wonder if (given my non–computer science background) I'd be better off starting in more “grounded” territory and going with Ruby or Python (the latter having the big advantage of being used for Sage, which I'd also like to investigate…after my PhD). Well, I guess this is pretty subjective, so perhaps I could rephrase: would it be better to start looking at Haskell (say) straight after an ad-hoc education to functional programming in Mathematica, or will I get more out of learning Python (say) first? In reference to the question "what do I want to do with it?", I guess my answer is "fun, and learning more". I've got this list of languages that I'd like to look at, and I don't know how to trim them down. And I'd rather start with something a little higher-level than C simply so that I can be somewhat productive without having to re-invent many wheels for any code I'd like to write.

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• Getting the type of an array of T, without specifying T - Type.GetType("T[]")

  - by Merlyn Morgan-Graham

  I am trying to create a type that refers to an array of a generic type, without specifying the generic type. That is, I would like to do the equivalent of Type.GetType("T[]"). I already know how to do this with a non-array type. E.g. Type.GetType("System.Collections.Generic.IEnumerable`1") // or typeof(IEnumerable<>) Here's some sample code that reproduces the problem. using System; using System.Collections.Generic; public class Program { public static void SomeFunc<T>(IEnumerable<T> collection) { } public static void SomeArrayFunc<T>(T[] collection) { } static void Main(string[] args) { Action<Type> printType = t => Console.WriteLine(t != null ? t.ToString() : "(null)"); Action<string> printFirstParameterType = methodName => printType( typeof(Program).GetMethod(methodName).GetParameters()[0].ParameterType ); printFirstParameterType("SomeFunc"); printFirstParameterType("SomeArrayFunc"); var iEnumerableT = Type.GetType("System.Collections.Generic.IEnumerable`1"); printType(iEnumerableT); var iEnumerableTFromTypeof = typeof(IEnumerable<>); printType(iEnumerableTFromTypeof); var arrayOfT = Type.GetType("T[]"); printType(arrayOfT); // Prints "(null)" // ... not even sure where to start for typeof(T[]) } } The output is: System.Collections.Generic.IEnumerable`1[T] T[] System.Collections.Generic.IEnumerable`1[T] System.Collections.Generic.IEnumerable`1[T] (null) I'd like to correct that last "(null)". This will be used to get an overload of a function via reflections by specifying the method signature: var someMethod = someType.GetMethod("MethodName", new[] { typeOfArrayOfT }); // ... call someMethod.MakeGenericMethod some time later I've already gotten my code mostly working by filtering the result of GetMethods(), so this is more of an exercise in knowledge and understanding.

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• Do the 'up to date' guarantees provided by final field in Java's memory model extend to indirect ref

  - by mattbh

  The Java language spec defines semantics of final fields in section 17.5: The usage model for final fields is a simple one. Set the final fields for an object in that object's constructor. Do not write a reference to the object being constructed in a place where another thread can see it before the object's constructor is finished. If this is followed, then when the object is seen by another thread, that thread will always see the correctly constructed version of that object's final fields. It will also see versions of any object or array referenced by those final fields that are at least as up-to-date as the final fields are. My question is - does the 'up-to-date' guarantee extend to the contents of nested arrays, and nested objects? An example scenario: Thread A constructs a HashMap of ArrayLists, then assigns the HashMap to final field 'myFinal' in an instance of class 'MyClass' Thread B sees a (non-synchronized) reference to the MyClass instance and reads 'myFinal', and accesses and reads the contents of one of the ArrayLists In this scenario, are the members of the ArrayList as seen by Thread B guaranteed to be at least as up to date as they were when MyClass's constructor completed?

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• How to preserve the state of JavaScript closure?

  - by Uccio

  I am working on a migration platform to migrate web applications from a device to another. I am extending it to add the support for preserving JavaScript state. My main task is to create a file representing the current state of the executing application, to transmit it to another device and to reload the state in the destination device. The basic solution I adopted is to navigate the window object and to save all its descendant properties using JSON as base format for exportation and extending it to implement some features: preserving object reference, even if cyclic (dojox.json.ref library) support for timers Date non-numericproperties of arrays reference to DOM elements The most important task I need to solve now is exportation of closures. At this moment I didn't know how to implement this feature. I read about the internal EcmaScript property [[scope]] containing the scope chain of a function, a list-like object composed by all the nested activation context of the function. Unfortunately it is not accessible by JavaScript. Anyone know if there is a way to directly access the [[scope]] property? Or another way to preserve the state of a closure?

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• How to map string keys to unique integer IDs?

  - by Marek

  I have some data that comes regularily as a dump from a data souce with a string natural key that is long (up to 60 characters) and not relevant to the end user. I am using this key in a url. This makes urls too long and user unfriendly. I would like to transform the string keys into integers with the following requirements: The source dataset will change over time. The ID should be: non negative integer unique and constant even if the set of input keys changes preferrably reversible back to key (not a strong requirement) The database is rebuilt from scratch every time so I can not remember the already assigned IDs and match the new data set to existing IDs and generate sequential IDs for the added keys. There are currently around 30000 distinct keys and the set is constantly growing. How to implement a function that will map string keys to integer IDs? What I have thought about: 1. Built-in string.GetHashCode: ID(key) = Math.Abs(key.GetHashCode()) is not guaranteed to be unique (not reversible) 1.1 "Re-hashing" the built-in GetHashCode until a unique ID is generated to prevent collisions. existing IDs may change if something colliding is added to the beginning of the input data set 2. a perfect hashing function I am not sure if this can generate constant IDs if the set of inputs changes (not reversible) 3. translate to base 36/64/?? does not shorten the long keys enough What are the other options?

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• Are there any other ways to iterate through the attributes of a custom class, excluding the in-built ones?

  - by Ricardo Altamirano

  Is there another way to iterate through only the attributes of a custom class that are not in-built (e.g. __dict__, __module__, etc.)? For example, in this code: class Terrain: WATER = -1 GRASS = 0 HILL = 1 MOUNTAIN = 2 I can iterate through all of these attributes like this: for key, value in Terrain.__dict__.items(): print("{: <11}".format(key), " --> ", value) which outputs: MOUNTAIN --> 2 __module__ --> __main__ WATER --> -1 HILL --> 1 __dict__ --> <attribute '__dict__' of 'Terrain' objects> GRASS --> 0 __weakref__ --> <attribute '__weakref__' of 'Terrain' objects> __doc__ --> None If I just want the integer arguments (a rudimentary version of an enumerated type), I can use this: for key, value in Terrain.__dict__.items(): if type(value) is int: # type(value) == int print("{: <11}".format(key), " --> ", value) this gives the expected result: MOUNTAIN --> 2 WATER --> -1 HILL --> 1 GRASS --> 0 Is it possible to iterate through only the non-in-built attributes of a custom class independent of type, e.g. if the attributes are not all integral. Presumably I could expand the conditional to include more types, but I want to know if there are other ways I'm missing.

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• PropertyPlaceholderConfigurer works from Maven command line, but not from Eclipse?

  - by HDave

  I have Eclipse configured to use an external maven instance. Nonetheless I have an integration test that runs fine from the command line, but fails from within Eclipse. The error is a class Spring application context bean error: Cannot convert value of type [java.lang.String] to required type The culprit it a bean that sets property values using a PropertyPlaceholderConfigurer. <!-- property settings for non-JNDI database connections --> <bean id="placeholderConfigUuid" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE" /> <property name="location" value="classpath:database.properties" /> <property name="placeholderPrefix" value="$DS{" /> </bean> I know which bean is failing because it appears in the stack trace and because when I replace the $DS{hibernate.dialect} with a static value it works. I have two questions: 1) Since M2Eclipse is using the same Maven setup as the command line, why does one work and the other fail? 2) How to fix this? I really like the ability to run a single jUnit test from within Eclipse on demand.

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• Pair equal operator overloading for inserting into set

  - by Petwoip

  I am trying to add a pair<int,int> to a set. If a pair shares the same two values as another in the set, it should not be inserted. Here's my non-working code: typedef std::pair<int, int> PairInt; template<> bool std::operator==(const PairInt& l, const PairInt& r) { return (l.first == r.first && l.second == r.second) || (l.first == r.second && l.second == r.first); } int main() { std::set<PairInt> intSet; intSet.insert(PairInt(1,3)); intSet.insert(PairInt(1,4)); intSet.insert(PairInt(1,4)); intSet.insert(PairInt(4,1)); } At the moment, the (4,1) pair gets added even though there is already a (1,4) pair. The final contents of the set are: (1 3) (1 4) (4 1) and I want it to be (1 3) (1 4) I've tried putting breakpoints in the overloaded method, but they never get reached. What have I done wrong?

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• template specialization for static member functions; howto?

  - by Rolle

  I am trying to implement a template function with handles void differently using template specialization. The following code gives me an "Explicit specialization in non-namespace scope" in gcc: template <typename T> static T safeGuiCall(boost::function<T ()> _f) { if (_f.empty()) throw GuiException("Function pointer empty"); { ThreadGuard g; T ret = _f(); return ret; } } // template specialization for functions wit no return value template <> static void safeGuiCall<void>(boost::function<void ()> _f) { if (_f.empty()) throw GuiException("Function pointer empty"); { ThreadGuard g; _f(); } } I have tried moving it out of the class (the class is not templated) and into the namespace but then I get the error "Explicit specialization cannot have a storage class". I have read many discussions about this, but people don't seem to agree how to specialize function templates. Any ideas?

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• LINQ to SQL Queries odd Materialization

  - by ptoinson

  I ran across an interesting Linq to SQL, uh, feature, the other day. Perhaps someone can give me a logical explanation for the reasoning behind the results. Take the code below as my example which utilizes the AdventureWorks database setup in a Linq to SQL DataContext. This is a clip from my unit test. The resulting customer returned from a call to both CustomerQuery_Test_01() and CustomerQuery_Test_02() is the same. However, the query executed on the SQLServer are different is a major way. The method CustomerQuery_Test_01 us causing the entire Customer table to be materialized, which the call to CustomerQuery_Test_02 is only causing the single customer to be materialized. The resulting SQL Queries are at the bottom of this post. Anyone have a good reason for this? To me, it was highly non-intuitive. protected virtual Customer GetByPrimaryKey(Func<Customer, bool> keySelection) { AdventureWorksDataContext context = new AdventureWorksDataContext(); return (from r in context.Customers select r).SingleOrDefault(keySelection); } [TestMethod] public void CustomerQuery_Test_01() { Customer customer = GetByPrimaryKey(c => c.CustomerID == 2); } [TestMethod] public void CustomerQuery_Test_02() { AdventureWorksDataContext context = new AdventureWorksDataContext(); Customer customer = (from r in context.Customers select r).SingleOrDefault(c => c.CustomerID == 2); } Query for CustomerQuery_Test_01 (notice the lack of a where clause) SELECT [t0].[CustomerID], [t0].[NameStyle], [t0].[Title], [t0].[FirstName], [t0].[MiddleName], [t0].[LastName], [t0].[Suffix], [t0].[CompanyName], [t0].[SalesPerson], [t0].[EmailAddress], [t0].[Phone], [t0].[PasswordHash], [t0].[PasswordSalt], [t0].[rowguid], [t0].[ModifiedDate] FROM [SalesLT].[Customer] AS [t0] Query for CustomerQuery_Test_02 (notice the where clause) SELECT [t0].[CustomerID], [t0].[NameStyle], [t0].[Title], [t0].[FirstName], [t0].[MiddleName], [t0].[LastName], [t0].[Suffix], [t0].[CompanyName], [t0].[SalesPerson], [t0].[EmailAddress], [t0].[Phone], [t0].[PasswordHash], [t0].[PasswordSalt], [t0].[rowguid], [t0].[ModifiedDate] FROM [SalesLT].[Customer] AS [t0] WHERE [t0].[CustomerID] = @p0

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• Wordpress jQuery Post Attachment Image Gallery?

  - by LearnWebCode

  Hi everyone, Curious if any of you have a good solution for the following situation... because I've never thought of anything myself and usually have to resort to custom fields like "post-image-1" through "post-image-10" and manually paste the file name of a jpg in. Which is a horrible solution and only works for tech savvy posters. Basically I want non-tech savvy users to be able to upload / attach (but not insert into the actual post content) multiple images to a post, which will be turned into a makeshift gallery. Then I want to output these attachments in a list down the page after the post, using basic jQuery lightbox gallery functionality. It doesn't have to be through attachments, it could be a stand alone plugin, as long as it offers customizable markup. Basically any solution that would achieve the same thing would be incredible. Has anyone done this before? Am I missing something terribly obvious? I don't even know what exactly to call this, so I haven't had much luck with my Google research so far :( Thanks!

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• List all foreign key constraints that refer to a particular column in a specific table

  - by Sid

  I would like to see a list of all the tables and columns that refer (either directly or indirectly) a specific column in the 'main' table via a foreign key constraint that has the ON DELETE=CASCADE setting missing. The tricky part is that there would be an indirect relationships buried across up to 5 levels deep. (example: ... great-grandchild- FK3 = grandchild = FK2 = child = FK1 = main table). We need to dig up the leaf tables-columns, not just the very 1st level. The 'good' part about this is that execution speed isn't of concern, it'll be run on a backup copy of the production db to fix any relational issues for the future. I did SELECT * FROM sys.foreign_keys but that gives me the name of the constraint - not the names of the child-parent tables and the columns in the relationship (the juicy bits). Plus the previous designer used short, non-descriptive/random names for the FK constraints, unlike our practice below The way we're adding constraints into SQL Server: ALTER TABLE [dbo].[UserEmailPrefs] WITH CHECK ADD CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] FOREIGN KEY([UserId]) REFERENCES [dbo].[UserMasterTable] ([UserId]) ON DELETE CASCADE GO ALTER TABLE [dbo].[UserEmailPrefs] CHECK CONSTRAINT [FK_UserEmailPrefs_UserMasterTable_UserId] GO The comments in this SO question inpire this question.

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• Efficiently get the size of a parameter pack up to a certain index

  - by NmdMystery

  I want to be able to determine the number of bytes that are in a subset of a parameter pack from 0 to a given index. Right now I'm using a non-constexpr way of doing this. Below is my code: template <size_t index, typename... args> struct pack_size_index; template <size_t index, typename type_t, typename... args> struct pack_size_index <index, type_t, args...> { static const size_t index_v = index; static const size_t value(void) { if (index_v > 0) { return sizeof(type_t) + pack_size_index<index - 1, args...>::value(); } return 0; } }; template <size_t index> struct pack_size_index <index> { static const size_t index_v = index; static const size_t value(void) { return 0; } }; Usage: //output: 5 (equal to 1 + 4) std::cout << pack_size_index<2, bool, float, int, double>::value() << std::endl; //output: 20 (equal to 8 + 8 + 4) std::cout << pack_size_index<3, double, double, float, int>::value() << std::endl; This gets the job done, but this uses runtime comparison and the resulting executable increases in size rapidly whenever this is used. What's a less expensive way of doing this?

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• Why use shorter VARCHAR(n) fields?

  - by chryss

  It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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• Core Data Errors vs Exceptions Part 3

  - by John Gallagher

  My question is similar to this one. Background I'm creating a large number of objects in a core data store using NSOperations to speed things up. I've followed all the Core Data multithreading rules - I've got a single persistent store coordinator and a managed object context per thread that on save is merging back to the main managed object context. The Problem When the number of threads running at once is more than 1, I get the exception logged on save of my core data store: NSExceptionHandler has recorded the following exception: NSInternalInconsistencyException -- optimistic locking failure What I've Tried My code that creates new entities is quite complex - it makes entities that have relationships with other entities that could be being created in a separate thread. If I replace my object creation routine with some very simple code just making non-related entries, everything works perfectly. Initially, as well as the exceptions, I was getting a save error saying core data couldn't save due to the merge failing. I read the docs and realised I needed a merge policy on the Managed Object Context I was saving to. I set this up and as this question states, the save error goes away, but the exception remains. My Question Do I need to worry about these exceptions? If I do need to get rid of the exceptions, any ideas on how I do it?

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• Jquery failure after site went live

  - by Brandon Condrey

  I have been designing a site for weeks using JQuery. I don't have a local server or a testing server so I just created a directory through FTP, '/testing'. Everything was working great in the testing directory. I attempted to go live tonight by moving all the files in '/testing' to the root directory and I changed all file paths and script sources accordingly. The site loads, but everything related to JQuery is non-functional. Javascript console gives errors of (just as an example from a plugin): '$.os.name' is not a function I'm at loss for what to do. I changed the paths referencing the JQuery library, installed a fresh copy of JQuery (to a new directory), etc. There is a wordpress installation in a different directory '/blog'. I've read about some compatibility issues with wordpress, but that seems to be related to using JQuery inside wordpress, which I am not. I'm not sure if any code would be beneficial since it was all functional in a different directory. Your help is greatly appreciated.

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• Use `require()` with `node --eval`

  - by rentzsch

  When utilizing node.js's newish support for --eval, I get an error (ReferenceError: require is not defined) when I attempt to use require(). Here's an example of the failure: $ node --eval 'require("http");' undefined:1 ^ ReferenceError: require is not defined at eval at <anonymous> (node.js:762:36) at eval (native) at node.js:762:36 $ Here's a working example of using require() typed into the REPL: $ node > require("http"); { STATUS_CODES: { '100': 'Continue' , '101': 'Switching Protocols' , '102': 'Processing' , '200': 'OK' , '201': 'Created' , '202': 'Accepted' , '203': 'Non-Authoritative Information' , '204': 'No Content' , '205': 'Reset Content' , '206': 'Partial Content' , '207': 'Multi-Status' , '300': 'Multiple Choices' , '301': 'Moved Permanently' , '302': 'Moved Temporarily' , '303': 'See Other' , '304': 'Not Modified' , '305': 'Use Proxy' , '307': 'Temporary Redirect' , '400': 'Bad Request' , '401': 'Unauthorized' , '402': 'Payment Required' , '403': 'Forbidden' , '404': 'Not Found' , '405': 'Method Not Allowed' , '406': 'Not Acceptable' , '407': 'Proxy Authentication Required' , '408': 'Request Time-out' , '409': 'Conflict' , '410': 'Gone' , '411': 'Length Required' , '412': 'Precondition Failed' , '413': 'Request Entity Too Large' , '414': 'Request-URI Too Large' , '415': 'Unsupported Media Type' , '416': 'Requested Range Not Satisfiable' , '417': 'Expectation Failed' , '418': 'I\'m a teapot' , '422': 'Unprocessable Entity' , '423': 'Locked' , '424': 'Failed Dependency' , '425': 'Unordered Collection' , '426': 'Upgrade Required' , '500': 'Internal Server Error' , '501': 'Not Implemented' , '502': 'Bad Gateway' , '503': 'Service Unavailable' , '504': 'Gateway Time-out' , '505': 'HTTP Version not supported' , '506': 'Variant Also Negotiates' , '507': 'Insufficient Storage' , '509': 'Bandwidth Limit Exceeded' , '510': 'Not Extended' } , IncomingMessage: { [Function: IncomingMessage] super_: [Function: EventEmitter] } , OutgoingMessage: { [Function: OutgoingMessage] super_: [Function: EventEmitter] } , ServerResponse: { [Function: ServerResponse] super_: [Circular] } , ClientRequest: { [Function: ClientRequest] super_: [Circular] } , Server: { [Function: Server] super_: { [Function: Server] super_: [Function: EventEmitter] } } , createServer: [Function] , Client: { [Function: Client] super_: { [Function: Stream] super_: [Function: EventEmitter] } } , createClient: [Function] , cat: [Function] } > Is there a way to use require() with node's --eval? I'm on node 0.2.6 on Mac OS X 10.6.5.

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• decoding jquery json data in php

  - by Mac Taylor

  hey guys recenlty i made a script to move objects and save the orders now i have a little to do to finish this script everything works fine , just one question : how can i save not numeric data in my json script this is my script : function updateWidgetData(){ var items=[]; $('.widget-title').each(function(){ var weightId=$(this).attr('id'); $('.column').each(function(){ var columnId=$(this).attr('id'); $('.widget', this).each(function(i){ var collapsed=0; if($(this).find('.widget-inside').css('display')=="none") collapsed=1; //Create Item object for current panel var item={ id: $(this).attr('id'), collapsed: collapsed, order : i, column: columnId, weight: weightId }; //Push item object into items array items.push(item); }); }); }); //Assign items array to sortorder JSON variable var sortorder={ items: items }; //Pass sortorder variable to server using ajax to save state $.post('updatePanels.php', 'data='+$.toJSON(sortorder), function(response){ if(response=="success") $("#console").html('<div class="success">Saved</div>').hide().fadeIn(1000); setTimeout(function(){ $('#console').fadeOut(1000); }, 2000); }); } and this is my php script : $data=json_decode($_POST["data"]); foreach($data->items as $item) { //Extract column number for panel $col_id=preg_replace('/[^\d\s]/', '', $item->column); //Extract id of the panel $widget_id=preg_replace('/[^\d\s]/', '', $item->id); $sql="UPDATE widgets SET column_id='$col_id', sort_no='".$item->order."', collapsed='".$item->collapsed."' WHERE id='".$widget_id."'"; mysql_query($sql) or die('Error updating widget DB'); } echo "success"; everything works fine till i use numeric value for columns' id but i need non numeric values forexample id='columnr' i want to extract r but i cant get it right any help plz !?

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• Storing same type but still getting an ArrayStoreException

  - by Firefoxx Pwnass

  I have strange problem. I have three classes. Book ( abstract ), and two subclasses ( Fiction, Nonfiction). I have created array of Book references. That array can hold both subclasse's objects. I'have following code for Fiction class. public class Fiction extends Book{ public Fiction(String title) { super(title); setPrice(); } public void setPrice() { super.price = 24.99; } } And the "same" code for Nonfiction class public class Nonfiction extends Book{ public Nonfiction(String title) { super(title); setPrice(); } public void setPrice() { super.price = 37.99; } } And this is Main program. import javax.swing.JOptionPane; public class Main { public static void main(String[] args) { Book[] book = new Fiction[6]; for(int i = 0; i<book.length; i++) { if(i<4) { String title = JOptionPane.showInputDialog("Enter fiction book, no "+i); book[i] = new Fiction(title); } else { String title = JOptionPane.showInputDialog("Enter non fiction book, no "+i); book[i] = new Nonfiction(title); } } for(int x = 0; x<book.length; x++) { System.out.println("Book named "+book[x].getTitle()+" costs "+book[x].getPrice()); } } } For any reason i'm getting ArrayStoreException on this line.. book[i] = new Nonfiction(title); But same code works for Fiction class. I checked java documentation and it says that this exception is thrown when i'm trying to store different objects in array ( like String and Int ), but in this case they are all the same objects. Both classes are children of superclass, that means, they are of the same type. I'm confsued. A little help here please?

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• In Java, can a final field be initialized from a constructor helper?

  - by csj

  I have a final non-static member: private final HashMap<String,String> myMap; I would like to initialize it using a method called by the constructor. Since myMap is final, my "helper" method is unable to initialize it directly. Of course I have options: I could implement the myMap initialization code directly in the constructor. MyConstructor (String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... // other initialization stuff unrelated to myMap } I could have my helper method build the HashMap, return it to the constructor, and have the constructor then assign the object to myMap. MyConstructor (String someThingNecessary) { myMap = InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } private HashMap<String,String> InitializeMyMap(String someThingNecessary) { HashMap<String,String> initializedMap = new HashMap<String,String>(); initializedMap.put("blah","blahblah"); // etc... return initializedMap; } Method #2 is fine, however, I'm wondering if there's some way I could allow the helper method to directly manipulate myMap. Perhaps a modifier that indicates it can only be called by the constructor? MyConstructor (String someThingNecessary) { InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } // helper doesn't work since it can't modify a final member private void InitializeMyMap(String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... }

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• Rails 4 testing bug?

  - by Jamato

  Situation: if we add two identic line items into a cart, we update line item quantity instead of adding a duplicate.In browser everything works fine but in unit testing section something fails because of an empty cycle in code. Which I wanted to use to update all prices. Why? Is that a unit test engine bug? LineItem.all and cart.line_items in process of testing produce two DIFFERENT structures. #<LineItem id: 980190964, product_id: 1, cart_id: 999, created_at: "2014-06-01 00:21:28", updated_at: "2014-06-01 00:21:28", quantity: 2, price: #<BigDecimal:ba0fb544,'0.4E1',9(27)>> #<LineItem id: 980190964, product_id: 1, cart_id: 999, created_at: "2014-06-01 00:21:28", updated_at: "2014-06-01 00:21:28", quantity: 1, price: #<BigDecimal:ba0d1b04,'0.4E1',9(27)>> cart.line_items guy did not update quantity Code itself (produces LineItem which is then saved in line_item_controller which calls this method) class Cart < ActiveRecord::Base has_many :line_items, dependent: :destroy def add_product(product_id) # LOOK THIS CYCLE BREAKS UNIT TEST, SRSLY, I MEAN IT line_items.each do |item| end current_item = line_items.find_by(product_id: product_id) fresh_price = Product.find_by(id: product_id).price if current_item current_item.quantity += 1 else current_item = line_items.build(product_id: product_id, price: fresh_price) end return current_item end ... Unit test code test "non-unique item added" do cart = Cart.new(:id => 999) line_item0 = cart.add_product(2) line_item0.save line_item1 = cart.add_product(1) line_item1.save assert_equal 2, cart.line_items.size #success line_item2 = cart.add_product(1) line_item2.save assert_equal 2, cart.line_items.size, "what?" assert cart.total_price > 15 #fail, prices are not enough, quantity of product1 = 1 #we get total price from quantity, it's a simple method in model end And once again: IT DOES WORK in browser as it should. Even with cycle. I feel so dumb right now...

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• Detect that the onscreen keyboard has been displayed on Windows Phone 7

  - by David_001

  Simple question: How do I detect that the onscreen keyboard has been displayed on windows mobile 7? Is there an event I can add a listener to? It takes up about half the screen and I want to scroll the view up when it gets displayed... EDIT: A comment below indicates more clearly what I'm trying to do: I have a textbox input, and as the user types into it an autocomplete dropdown appears below it (like google suggest). By default, the active control (the textbox) scrolls into view when focussed, and the onscreen keyboard is directly below it. The onscreen keyboard appears in front of my autocomplete dropdown - what I want to do is make the screen scroll a little further up, so there's some room for my dropdown to be shown. The windows phone UI design guidelines say: "When the keyboard is deployed, the application should scroll to ensure the active edit control and the caret are in view". This happens fine, it's just the non-active dropdown gets hidden behind the onscreen keyboard. The guidelines also say that an application can choose to show the onscreen keyboard, and can also choose to close it. At the moment i'm stuck, and I don't think (based on my research and the replies to this question) that it's possible to detect that the onscreen keyboard has been displayed. I'm moving my investigation to see if it's possible to determine the "visible area" of the page (width & height in pixels for example), and combine this with an onfocus for the textbox... not sure if this will prove fruitful though.

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• jQuery class selector and click()

  - by Anonymous

  I'm currently trying to get an alert to happen when something is clicked. I can get it working in jsFiddle, but not in production code: jsFiddle example that works (jQuery 1.5 loaded) HTML (in case jsFiddle is inaccessible): <!DOCTYPE HTML><html><head><title>Test</title></head> <body> <h1>25 Feb 2011</h1><h3>ABC</h3><ul> <li class="todoitem">Test&mdash;5 minutes</li> </ul> </body></html> Javascript: $(".todoitem").click(function() { alert('Item selected'); }); Non-working production example: <!DOCTYPE HTML><html><head><title>Test</title> <script src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.5.1.min.js" type="text/javascript"></script> <script type="text/javascript"> $(".todoitem").click(function() { alert('Item selected'); }); </script> </head> <body> <h1>25 Feb 2011</h1><h3>ABC</h3><ul><li class="todoitem">Test&mdash;5 minutes</li></ul> </body> </html> Safari's Inspector indicate that jQuery is being loaded correctly, so that's not the issue. As far as I can tell, these two pieces of code are essentially identical, but the latter isn't working. Can anyone see what I've done wrong?

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• Show menu when view is long pressed

  - by swift1691

  I've been looking around on the internet regarding my question but I couldn't find a straight answer. Is it possible to create a non-blocking menu similar to the overflow menu found in Android 4.0+ when a view is long pressed? I have a number of LinearLayout instances which have an OnLongClickListener which brings up a context menu, but it's not exactly what I am looking for. I was hoping for a smoother menu which is brought up when one of these instances is clicked, and removed when the user clicks outside of the menu's region. This is very similar to the way the overflow menu behaves in the Android ActionBar. So to sum up, is it possible to replicate the look-and-fell and the behavior of the overflow menu when using context menus? Here's hoping I don't have to jump through hoops to get the implementation that I desire. Thanks in advance. EDIT: After some digging I've found the PopupMenu which is exactly what I was looking for however it works only on devices running Honeycomb and above. Does anyone know of a way with which I can replicate this menu behavior in older versions of Android without using blocking windows like dialogs?

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• Best ways to format LINQ queries.

  - by Aren B

  Before you ignore / vote-to-close this question, I consider this a valid question to ask because code clarity is an important topic of discussion, it's essential to writing maintainable code and I would greatly appreciate answers from those who have come across this before. I've recently run into this problem, LINQ queries can get pretty nasty real quick because of the large amount of nesting. Below are some examples of the differences in formatting that I've come up with (for the same relatively non-complex query) No Formatting var allInventory = system.InventorySources.Select(src => new { Inventory = src.Value.GetInventory(product.OriginalProductId, true), Region = src.Value.Region }).GroupBy(i => i.Region, i => i.Inventory); Elevated Formatting var allInventory = system.InventorySources .Select(src => new { Inventory = src.Value.GetInventory(product.OriginalProductId, true), Region = src.Value.Region }) .GroupBy( i => i.Region, i => i.Inventory); Block Formatting var allInventory = system.InventorySources .Select( src => new { Inventory = src.Value.GetInventory(product.OriginalProductId, true), Region = src.Value.Region }) .GroupBy( i => i.Region, i => i.Inventory ); List Formatting var allInventory = system.InventorySources .Select(src => new { Inventory = src.Value.GetInventory(product.OriginalProductId, true), Region = src.Value.Region }) .GroupBy(i => i.Region, i => i.Inventory); I want to come up with a standard for linq formatting so that it maximizes readability & understanding and looks clean and professional. So far I can't decide so I turn the question to the professionals here.

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