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• What's a good Java-based Master-Slave communication mechanism?

  - by plecong

  I'm creating a Java application that requires master-slave communication between JVMs, possibly residing on the same physical machine. There will be a "master" server running inside a JEE application server (i.e. JBoss) that will have "slave" clients connect to it and dynamically register itself for communication (that is the master will not know the IP addresses/ports of the slaves so cannot be configured in advance). The master server acts as a controller that will dole work out to the slaves and the slaves will periodically respond with notifications, so there would be bi-directional communication. I was originally thinking of RPC-based systems where each side would be a server, but it could get complicated, so I'd prefer a mechanism where there's an open socket and they talk back and forth. I'm looking for a communication mechanism that would be low-latency where the messages would be mostly primitive types, so no serious serialization is necessary. Here's what I've looked at: RMI JMS: Built-in to Java, the "slave" clients would connect to the existing ConnectionFactory in the application server. JAX-WS/RS: Both master and slave would be servers exposing an RPC interface for bi-directional communication. JGroups/Hazelcast: Use shared distributed data structures to facilitate communication. Memcached/MongoDB: Use these as "queues" to facilitate communication, though the clients would have to poll so there would be some latency. Thrift: This does seem to keep a persistent connection, but not sure how to integrate/embed a Thrift server into JBoss WebSocket/Raw Socket: This would work, but require a lot more custom code than I'd like. Is there any technology I'm missing? Edit: Also looked at: JMX: Have the client connect to JBoss' JMX server and receive JMX notifications for bidirectional comms.

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• Is there a safe / standard way to manage unstructured memory in C++?

  - by andand

  I'm building a toy VM that requires a block of memory for storing and accessing data elements of different types and of different sizes. I've done this by writing a wrapper class around a uint8_t[] data block of the needed size. That class has some template methods to write / read typed data elements to / from arbitrary locations in the memory block, both of which check to make certain the bounds aren't violated. These methods use memmove in what I hope is a more or less safe manner. That said, while I am willing to press on in this direction, I've got to believe that other with more expertise have been here before and might be willing to share their wisdom. In particular: 1) Is there a class in one of the C++ standards (past, present, future) that has been defined to perform a function similar to what I have outlined above? 2) If not, is there a (preferably free as in beer) library out there that does? 3) Short of that, besides bounds checking and the inevitable issue of writing one type to a memory location and reading a different from that location, are there other issues I should be aware of? Thanks.-&&

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• Mapping enum with fluent nhibernate

  - by Puneet

  I am following the http://wiki.fluentnhibernate.org/Getting%5Fstarted tutorial to create my first NHibernate project with Fluent NHibernate I have 2 tables 1) Account with fields Id AccountHolderName AccountTypeId 2) AccountType with fields Id AccountTypeName Right now the account types can be Savings or Current So the table AccountTypes stores 2 rows 1 - Savings 2 - Current For AccoutType table I have defined enum public enum AccountType { Savings=1, Current=2 } For Account table I define the entity class public class Account { public virtual int Id {get; private set;} public virtual string AccountHolderName {get; set;} public virtual string AccountType {get; set;} } The fluent nhibernate mappings are: public AgencyMap() { Id(o => o.Id); Map(o => o.AccountHolderName); Map(o => o.AccountType); } When I try to run the solution, it gives an exception - InnerException = {"(XmlDocument)(2,4): XML validation error: The element 'class' in namespace 'urn:nhibernate-mapping-2.2' has incomplete content. List of possible elements expected: 'meta, subselect, cache, synchronize, comment, tuplizer, id, composite-id' in namespace 'ur... I guess that is because I have not speciofied any mapping for AccountType. The questions are: How can I use AccountType enum instead of a AccountType class? Maybe I am going on wrong track. Is there a better way to do this? Thanks!

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• Best practice - logging events (general) and changes (database)

  - by b0x0rz

  need help with logging all activities on a site as well as database changes. requirements: * should be in database * should be easily searchable by initiator (user name / session id), event (activity type) and event parameters i can think of a database design but either it involves a lot of tables (one per event) so i can log each of the parameters of an event in a separate field OR it involves one table with generic fields (7 int numeric and 7 text types) and log everything in one table with event type field determining what parameter got written where (and hoping that i don't need more than 7 fields of a certain type, or 8 or 9 or whatever number i choose)... example of entries (the usual things): [username] login failed @datetime [username] login successful @datetime [username] changed password @datetime, estimated security of password [low/ok/high/perfect] @datetime [username] clicked result [result number] [result id] after searching for [search string] and got [number of results] @datetime [username] clicked result [result number] [result id] after searching for [search string] and got [number of results] @datetime [username] changed profile name from [old name] to [new name] @datetime [username] verified name with [credit card type] credit card @datetime datbase table [table name] purged of old entries @datetime via automated process etc... so anyone dealt with this before? any best practices / links you can share? i've seen it done with the generic solution mentioned above, but somehow that goes against what i learned from database design, but as you can see the sheer number of events that need to be trackable (each user will be able to see this info) is giving me headaches, BUT i do LOVE the one event per table solution more than the generic one. any thoughts? edit: also, is there maybe an authoritative list of such (likely) events somewhere? thnx stack overflow says: the question you're asking appears subjective and is likely to be closed. my answer: probably is subjective, but it is directly related to my issue i have with designing a database / writing my code, so i'd welcome any help. also i tried narrowing down the ideas to 2 so hopefully one of these will prevail, unless there already is an established solution for these kinds of things.

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• Type-safe mapping from Class<T> to Thing<T>

  - by Joonas Pulakka

  I want to make a map-kind of container that has the following interface: public <T> Thing<T> get(Class<T> clazz); public <T> void put(Class<T> clazz, Thing<T> thing); The interesting point is that the Ts in each Class<T><- Thing<T> pair is the same T, but the container should be able to hold many different types of pairs. Initially I tried a (Hash)Map. But, for instance, Map<Class<T>, Thing<T>> is not right, because then T would be same T for all pairs in that map. Of course, Map<Class<?>, Thing<?>> works, but then I don't have type-safety guarantees so that when I get(String.class), I can't be sure that I get a Thing<String> instance back. Is there a way to accomplish the kind of type safety that I'm looking for?

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• Java inheritance and super() isn't working as expected

  - by dwwilson66

  For a homework assignment, I'm working with the following. It's an assigned class structure, I know it's not the best design by a long shot. Class | Extends | Variables -------------------------------------------------------- Person | None | firstName, lastName, streetAddress, zipCode, phone CollegeEmployee | Person | ssn, salary,deptName Faculty | CollegeEmployee | tenure(boolean) Student | person | GPA,major So in the Faculty class... public class Faculty extends CollegeEmployee { protected String booleanFlag; protected boolean tenured; public Faculty(String firstName, String lastName, String streetAddress, String zipCode, String phoneNumber,String ssn, String department,double salary) { super(firstName,lastName,streetAddress,zipCode,phoneNumber, ssn,department,salary); String booleanFlag = JOptionPane.showInputDialog (null, "Tenured (Y/N)?"); if(booleanFlag.equals("Y")) tenured = true; else tenured = false; } } It was my understanding that super() in Faculty would allow access to the variables in CollegeEmployee as well as Person. With the code above, it compiles fine when I ONLY include the Person variables. As soon as I try to use ssn, department, or salary I get the following compile errors. Faculty.java:15: error: constructor CollegeEmployee in class CollegeEmployee can not be applied to the given types: super(firstName,lastName,streetAddress,zipCode,phoneNumber,ssn,department,salary); ^ Required: String,String,String,String,String Found: String,String,String,String,String,String,String,String reason: actual and formal argument lists differ in length I'm completely confused by this error...which is the actual and formal? Person has five arguments, CollegeEmployee has 3, so my guess is that something's funky with how the parameters are being passed...but I'm not quite sure where to begin fixing it. What am I missing?

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• Reordering methods in ComImport interfaces throws COMException (0x80041001)

  - by Ohad Schneider

  Consider the following code for COM interop with internet shortcuts: [ComImport] [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] [Guid("CABB0DA0-DA57-11CF-9974-0020AFD79762")] public interface IUniformResourceLocatorW { void SetUrl([MarshalAs(UnmanagedType.LPWStr)] string pcszUrl, int dwInFlags); void GetUrl([MarshalAs(UnmanagedType.LPWStr)] out StringBuilder ppszUrl); void InvokeCommand(IntPtr purlici); } [ComImport] [Guid("FBF23B40-E3F0-101B-8488-00AA003E56F8")] public class InternetShortcut { } The following works as expected: var ishort = new InternetShortcut(); ((IPersistFile)ishort).Load("MyLink.url", 0); ((IUniformResourceLocatorW)ishort).GetUrl(out url); However: If I comment out IUniformResourceLocatorW.SetUrl (which I am not using), IUniformResourceLocatorW.GetUrl throws a COMException (HResult 0x80041001). If I switch between IUniformResourceLocatorW.SetUrl and IUniformResourceLocatorW.GetUrl (that is place the former below the latter) the same exception is thrown If I comment out IUniformResourceLocatorW.InvokeCommand the code runs fine. It's as if the order has to be preserved "up to" the invoked method. Is this behavior by design? documented somewhere? I'm asking because some COM interfaces are composed of many methods with possibly many supporting types and I'd rather avoid defining what I don't need if possible.

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• How is it legal to reference an undefined type inside a structure?

  - by paxdiablo

  As part of answering another question, I came across a piece of code like this, which gcc compiles without complaint. typedef struct { struct xyz *z; } xyz; int main (void) { return 0; } This is the means I've always used to construct types that point to themselves (e.g., linked lists) but I've always thought you had to name the struct so you could use self-reference. In other words, you couldn't use xyz *z within the structure because the typedef is not yet complete at that point. But this particular sample does not name the structure and it still compiles. I thought originally there was some black magic going on in the compiler that automatically translated the above code because the structure and typedef names were the same. But this little beauty works as well: typedef struct { struct NOTHING_LIKE_xyz *z; } xyz; What am I missing here? This seems a clear violation since there is no struct NOTHING_LIKE_xyz type defined anywhere. When I change it from a pointer to an actual type, I get the expected error: typedef struct { struct NOTHING_LIKE_xyz z; } xyz; qqq.c:2: error: field `z' has incomplete type Also, when I remove the struct, I get an error (parse error before "NOTHING ...). Is this allowed in ISO C?

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• How to Declare Complex Nested C# Type for Web Service

  - by TheArtTrooper

  I would like to create a service that accepts a complex nested type. In a sample asmx file I created: [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. // [System.Web.Script.Services.ScriptService] public class ServiceNest : System.Web.Services.WebService { public class Block { [XmlElement(IsNullable = false)] public int number; } public class Cell { [XmlElement(IsNullable = false)] public Block block; } public class Head { [XmlElement(IsNullable = false)] public Cell cell; } public class Nest { public Head head; } [WebMethod] public void TakeNest(Nest nest) { } } When I view the asmx file in IE the test page shows the example SOAP post request as: <?xml version="1.0" encoding="utf-8"?> <soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Body> <TakeNest xmlns="http://schemas.intellicorp.com/livecompare/"> <nest> <head> <cell> <block xsi:nil="true" /> </cell> </head> </nest> </TakeNest> </soap:Body> </soap:Envelope> It hasn't expanded the <block> into its number member. Looking at the WSDL, the types all look good. So is this just a limitation of the post demo page creator? Thanks.

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• best practice - loging events (general) and changes (database)

  - by b0x0rz

  need help with logging all activities on a site as well as database changes. requirements: * should be in database * should be easily searchable by initiator (user name / session id), event (activity type) and event parameters i can think of a database design but either it involves a lot of tables (one per event) so i can log each of the parameters of an event in a separate field OR it involves one table with generic fields (7 int numeric and 7 text types) and log everything in one table with event type field determining what parameter got written where (and hoping that i don't need more than 7 fields of a certain type, or 8 or 9 or whatever number i choose)... example of entries (the usual things): [username] login failed @datetime [username] login successful @datetime [username] changed password @datetime, estimated security of password [low/ok/high/perfect] @datetime [username] clicked result [result number] [result id] after searching for [search string] and got [number of results] @datetime [username] clicked result [result number] [result id] after searching for [search string] and got [number of results] @datetime [username] changed profile name from [old name] to [new name] @datetime [username] verified name with [credit card type] credit card @datetime datbase table [table name] purged of old entries @datetime etc... so anyone dealt with this before? any best practices / links you can share? i've seen it done with the generic solution mentioned above, but somehow that goes against what i learned from database design, but as you can see the sheer number of events that need to be trackable (each user will be able to see this info) is giving me headaches, BUT i do LOVE the one event per table solution more than the generic one. any thoughts? edit: also, is there maybe an authoritative list of such (likely) events somewhere? thnx stack overflow says: the question you're asking appears subjective and is likely to be closed. my answer: probably is subjective, but it is directly related to my issue i have with designing a database / writing my code, so i'd welcome any help. also i tried narrowing down the ideas to 2 so hopefully one of these will prevail, unless there already is an established solution for these kinds of things.

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• Application Design: Single vs. Multiple Hits to the DB

  - by shyneman

  I'm building a service that performs a set of configured activities based on the type of request that it receives. Each activity involves going to the database and retrieving/updating some kind of information. The logic for each activity can be generalized and re-used across different request types. The activities may need to participate in a transaction for the duration of the servicing the request. One option, I'm considering is having each activity maintain its own access to DAL/database. This fully encapsulates the activity into a stand-alone re-usable piece, but hitting the database multiple times for one request doesn't seem like a viable option. I don't really know how to easily implement the concept of a transaction across the multiple activities here either. The second option is to encapsulate ALL the activities into one big activity and hit the database once. But this does not allow re-use and configuration of these activities for different requests. Does anyone have any suggestions and input about what should be the best way to approach my problem? Thanks for any help.

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• How do I format the contents of a DataGrid cell as a Date? as Currency?

  - by Ben McCormack

  I have a Silverlight DataGrid that's being populated with different types of data for each column. I'm trying to figure out how to format some of the contents of the DataGrid's cells, specifically for dates and formatting. I have a date column that's currently displaying like: 3/11/2010 12:00:00 AM. I would rather it display like 3/14/2010. I have a number column that's currently displaying like: 51.32. I'd rather it display as currency like $51.32. I'm not sure how I can go about doing this. I'd prefer to do it in XAML instead of C#, but both solutions are fine. For reference, here's my XAML so far: </data:DataGridTextColumn> <data:DataGridTextColumn Header="Payee" Binding="{Binding Payee}"/> <data:DataGridTextColumn Header="Category" Binding="{Binding Category}"/> <data:DataGridTextColumn Header="Memo" Binding="{Binding Memo}"/> <data:DataGridTextColumn Header="Inflow" Binding="{Binding Inflow}"/> <data:DataGridTextColumn Header="Outflow" Binding="{Binding Outflow}"/> </data:DataGrid.Columns>

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• How to update GUI thread/class from worker thread/class?

  - by user315182

  First question here so hello everyone. The requirement I'm working on is a small test application that communicates with an external device over a serial port. The communication can take a long time, and the device can return all sorts of errors. The device is nicely abstracted in its own class that the GUI thread starts to run in its own thread and has the usual open/close/read data/write data basic functions. The GUI is also pretty simple - choose COM port, open, close, show data read or errors from device, allow modification and write back etc. The question is simply how to update the GUI from the device class? There are several distinct types of data the device deals with so I need a relatively generic bridge between the GUI form/thread class and the working device class/thread. In the GUI to device direction everything works fine with [Begin]Invoke calls for open/close/read/write etc. on various GUI generated events. I've read the thread here (How to update GUI from another thread in C#?) where the assumption is made that the GUI and worker thread are in the same class. Google searches throw up how to create a delegate or how to create the classic background worker but that's not at all what I need, although they may be part of the solution. So, is there a simple but generic structure that can be used? My level of C# is moderate and I've been programming all my working life, given a clue I'll figure it out (and post back)... Thanks in advance for any help.

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• Function should return float, but it gets messed up!

  - by Andre

  Hi guys, I'm going crazy here. I have a function that should return a float number: - (float) getHue:(UIColor *)original { NSLog(@"getHue"); const CGFloat *componentColors = CGColorGetComponents(original.CGColor); float red = componentColors[0]; float green = componentColors[1]; float blue = componentColors[2]; float h = 0.0f; float maxChannel = fmax(red, fmax(green, blue)); float minChannel = fmin(red, fmin(green, blue)); if (maxChannel == minChannel) h = 0.0f; else if (maxChannel == red) h = 0.166667f * (green - blue) / (maxChannel - minChannel) + 0.000000f; else if (maxChannel == green) h = 0.166667f * (blue - red) / (maxChannel - minChannel) + 0.333333f; else if (maxChannel == blue) h = 0.166667f * (red - green) / (maxChannel - minChannel) + 0.666667f; else h = 0.0f; if (h < 0.0f) h += 1.0f; NSLog(@"getHue results: %f", h); return h; } The NSLog will trace it correctly (i.e: 0.005), but the actual return value of the function is NULL. I've tried getting that value in so many ways and it never works. float originalHue = [self getHue:original]; results in a building error, as it says: "incompatible types in initialization" float *originalHue = [self getHue:original]; results in a null return. I've tried other ways, but it never actually gets the value properly. Any thoughts? Cheers guys, Andre

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• Passing an arbitrary JSONValue to a JSNI function

  - by Riley Lark

  I have a JSONValue in my Java that may be a JSONArray, a JSONObject, a JSONString, etc. I want to pass it to a JSNI function that can accept any of those types. If I naively write my JSNI as something like: public final native jsni(Object parameter) /*-{ doSomething(parameter); }-*/; public void useFunction(JSONValue value) { jsni(value); //Throws js exception at runtime :( } then I get a javascript exception, because GWT doesn't know how to convert the JSONValue to a JavaScriptObject (or native string / number value). My current workaround is public final native jsniForJSO(Object parameter) /*-{ doSomething(parameter); }-*/; public final native jsniForString(String parameter) /*-{ doSomething(parameter); }-*/; public final native jsniForNumber(double parameter) /*-{ doSomething(parameter); }-*/; public actuallyUseFunction(JSONValue value) { if (value.isObject()) { jsniForJSO(value.isObject().getJavaScriptObject()); } else if (value.isString()) { jsniForString(value.isString().stringValue()); } else { //etc } } This is a big burden for code maintainability, etc... especially if you have more than one parameter. Is there a way to generate these functions automatically, or get around this issue altogether? I've taken to wrapping everything in a JSONObject first, so I can definitely get a JavaScriptObject to pass to my jsni, but that's another clumsy mechanic.

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• How to define trees with more than one type in ML programing language

  - by user550413

  Well, I am asked to do the next thing: To define a binary tree which can contain 2 different types: ('a,'b) abtree and these are the requirements: Any inner vertex (not a leaf) must be of the type 'a or 'b and the leafs have no value. For every path in the tree all 'a values must appear before the 'b value: examples of paths: 'a->'a->'a-'b (legal) 'a->'b->'b (legal) 'a->'a->'a (legal) 'b->'b->'b (legal) 'a->'b->'a (ILLEGAL) and also I need to define another tree which is like the one described above but now I have got also 'c and in the second requirement it says that for every path I 'a values appear before the 'b values and all the 'b values appear before the 'c values. First, I am not sure how to define binary trees to have more than 1 type in them. I mean the simplest binary tree is: datatype 'a tree = leaf | br of 'a * 'a tree * 'a tree; And also how I can define a tree to have these requirements. Any help will be appreciated. Thanks.

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• Can I get rid of this read lock?

  - by Pieter

  I have the following helper class (simplified): public static class Cache { private static readonly object _syncRoot = new object(); private static Dictionary<Type, string> _lookup = new Dictionary<Type, string>(); public static void Add(Type type, string value) { lock (_syncRoot) { _lookup.Add(type, value); } } public static string Lookup(Type type) { string result; lock (_syncRoot) { _lookup.TryGetValue(type, out result); } return result; } } Add will be called roughly 10/100 times in the application and Lookup will be called by many threads, many of thousands of times. What I would like is to get rid of the read lock. How do you normally get rid of the read lock in this situation? I have the following ideas: Require that _lookup is stable before the application starts operation. The could be build up from an Attribute. This is done automatically through the static constructor the attribute is assigned to. Requiring the above would require me to go through all types that could have the attribute and calling RuntimeHelpers.RunClassConstructor which is an expensive operation; Move to COW semantics. public static void Add(Type type, string value) { lock (_syncRoot) { var lookup = new Dictionary<Type, string>(_lookup); lookup.Add(type, value); _lookup = lookup; } } (With the lock (_syncRoot) removed in the Lookup method.) The problem with this is that this uses an unnecessary amount of memory (which might not be a problem) and I would probably make _lookup volatile, but I'm not sure how this should be applied. (John Skeets' comment here gives me pause.) Using ReaderWriterLock. I believe this would make things worse since the region being locked is small. Suggestions are very welcome.

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• boost::spirit (qi) decision between float and double

  - by ChrisInked

  I have a parser which parses different data types from an input file. I already figured out, that spirit can decide between short and int, for example: value %= (shortIntNode | longIntNode); with shortIntNode %= (qi::short_ >> !qi::double_) [qi::_val = phoenix::bind(&CreateShortIntNode, qi::_1)]; longIntNode %= (qi::int_ >> !qi::double_) [qi::_val = phoenix::bind(&CreateLongIntNode, qi::_1)]; I used this type of rules to detect doubles as well (from the answers here and here). The parser was able to decide between int for numbers 65535 and short for numbers <= 65535. But, for float_ and double_ it does not work as expected. It just rounds these values to parse it into a float value, if there is a rule like this: value %= (floatNode | doubleFloatNode); with floatNode %= (qi::float_) [qi::_val = phoenix::bind(&CreateFloatNode, qi::_1)]; doubleFloatNode %= (qi::double_) [qi::_val = phoenix::bind(&CreateDoubleFloatNode, qi::_1)]; Do you know if there is something like an option or some other trick to decide between float_ and double_ depending on the data type range? Thank you very much!

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• Why does first call to java.io.File.createTempFile(String,String,File) take 5 seconds on Citrix?

  - by Ben Roling

  While debugging slow startup of an Eclipse RCP app on a Citrix server, I came to find out that java.io.createTempFile(String,String,File) is taking 5 seconds. It does this only on the first execution and only for certain user accounts. Specifically, I am noticing it Citrix anonymous user accounts. I have not tried many other types of accounts, but this behavior is not exhibited with an administrator account. Also, it does not matter if the user has access to write to the given directory or not. If the user does not have access, the call will take 5 seconds to fail. If they do have access, the call with take 5 seconds to succeed. This is on a Windows 2003 Server. I've tried Sun's 1.6.0_16 and 1.6.0_19 JREs and see the same behavior. I googled a bit expecting this to be some sort of known issue, but didn't find anything. It seems like someone else would have had to have run into this before. The Eclipse Platform uses File.createTempFile() to test various directories to see if they are writeable during initialization and this issue adds 5 seconds to the startup time of our application. I imagine somebody has run into this before and might have some insight. Here is sample code I executed to see that it is indeed this call that is consuming the time. I also tried it with a second call to createTempFile and notice that subsequent calls return nearly instantaneously. public static void main(final String[] args) throws IOException { final File directory = new File(args[0]); final long startTime = System.currentTimeMillis(); File file = null; try { file = File.createTempFile("prefix", "suffix", directory); System.out.println(file.getAbsolutePath()); } finally { System.out.println(System.currentTimeMillis() - startTime); if (file != null) { file.delete(); } } } Sample output of this program is the following: C:\java.exe -jar filetest.jar C:/Temp C:\Temp\prefix8098550723198856667suffix 5093

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• Machine leaning algorithm for data classification.

  - by twk

  Hi all, I'm looking for some guidance about which techniques/algorithms I should research to solve the following problem. I've currently got an algorithm that clusters similar-sounding mp3s using acoustic fingerprinting. In each cluster, I have all the different metadata (song/artist/album) for each file. For that cluster, I'd like to pick the "best" song/artist/album metadata that matches an existing row in my database, or if there is no best match, decide to insert a new row. For a cluster, there is generally some correct metadata, but individual files have many types of problems: Artist/songs are completely misnamed, or just slightly mispelled the artist/song/album is missing, but the rest of the information is there the song is actually a live recording, but only some of the files in the cluster are labeled as such. there may be very little metadata, in some cases just the file name, which might be artist - song.mp3, or artist - album - song.mp3, or another variation A simple voting algorithm works fairly well, but I'd like to have something I can train on a large set of data that might pick up more nuances than what I've got right now. Any links to papers or similar projects would be greatly appreciated. Thanks!

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• Parsing a JSON feed from YQL using jQuery

  - by Keith

  I am using YQL's query.multi to grab multiple feeds so I can parse a single JSON feed with jQuery and reduce the number of connections I'm making. In order to parse a single feed, I need to be able to check the type of result (photo, item, entry, etc) so I can pull out items in specific ways. Because of the way the items are nested within the JSON feed, I'm not sure the best way to loop through the results and check the type and then loop through the items to display them. Here is a YQL (http://developer.yahoo.com/yql/console/) query.multi example and you can see three different result types (entry, photo, and item) and then the items nested within them: select * from query.multi where queries= "select * from twitter.user.timeline where id='twitter'; select * from flickr.photos.search where has_geo='true' and text='san francisco'; select * from delicious.feeds.popular" or here is the JSON feed itself: http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20query.multi%20where%20queries%3D%22select%20*%20from%20flickr.photos.search%20where%20user_id%3D'23433895%40N00'%3Bselect%20*%20from%20delicious.feeds%20where%20username%3D'keith.muth'%3Bselect%20*%20from%20twitter.user.timeline%20where%20id%3D'keithmuth'%22&format=json&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=

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• Silverlight vs Flex

  - by 1kevgriff

  My company develops several types of applications. A lot of our business comes from doing multimedia-type apps, typically done in Flash. However, now that side of the house is starting to migrate towards doing Flex development. Most of our other development is done using .NET. I'm trying to make a push towards doing Silverlight development instead, since it would take better advantage of the .NET developers on staff. I prefer the Silverlight platform over the Flex platform for the simple fact that Silverlight is all .NET code. We have more .NET developers on staff than Flash/Flex developers, and most of our Flash/Flex developers are graphic artists (not real programmers). Only reason they push towards Flex right now is because it seems like the logical step from Flash. I've done development using both, and I honestly believe Silverlight is easier to work with. But I'm trying to convince people who are only Flash developers. So here's my question: If I'm going to go into a meeting to praise Silverlight, why would a company want to go with Silverlight instead of Flex? Other than the obvious "not everyone has Silverlight", what are the pros and cons for each?

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• Problem in filtering records using Dataview (C#3.0)

  - by Newbie

  I have a data table . The data table is basically getting populated from excel sheet. And there are many excel sheets. Henceforth, I have written a utility method for accomplishing the same. Now in some of the excel sheets, there are date columns and in some it is not(only text/string). My function is populating the values properly into the datatable from the excell sheet. But there are many blank rows in the excel sheets some are filled with NULL , some with " ". So I need to filter those records (which are NULL or " " ) first before further processing. What I am after is to use a dataview and apply the filter over there. DataView dv = dataTable.DefaultView; dv.RowFilter = ColumnName + " <> ''"; Well by using metedata (GetOleDbSchemaTable(OleDbSchemaGuid.Columns, restrection)) I was able to get the column names from the excel sheet , so getting the column names is not an issue. But the problem is as I said in some Excel sheet there are date fileds some are not. So the Filter condition of the Dataview needs to be proper. If I apply the above logic, and if it encounters a Datafield, it is throwing error Cannot perform '<' operation on System.DateTime and System.String. Could you people please help me out? I need to filter columns(not known at compile time + their data types) which can have NULL and " " I am using C#3.0 Thanks

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• Static files in (Java) App Engine not accessible.

  - by fiXedd

  The example documentation says that you simply need to place your files in war/ (or a subdirectory) and they should be accessible from the host (as long as they aren't JSPs or in WEB-INF). For example, if you place foo.css in war/ then you should be able to access it at http://localhost:8080/foo.css. However, this isn't working for me at all. NONE of my static files are accessible. The docs on appengine-web.xml say that you can also specifically denote certain types as static. I've tried this as well and it makes no difference. Am I missing something obvious? UPDATE: Turns out one of the mappings in my web.xml was a little too aggressive. The following was the culprit: <servlet> <servlet-name>Main</servlet-name> <servlet-class>MainServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>Main</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> It seems that it was grabbing everything that wasn't grabbed be one of the other rules, which I don't understand because there was no * on the end of the url-pattern. It also seems to be directly contradictory to the documentation that says: Note: Static files, files that are served verbatim to users such as images, CSS or JavaScript, are handled separately from paths mentioned in the deployment descriptor. A request for a URL path that matches a path to a file in the WAR that's considered a static file will serve the file, regardless of servlet and filter mappings in the deployment descriptor. You can exclude files from those treated as static files using the appengine-web.xml file. So, how can I have a rule that matches the base of my domain (eg. http://www.example.com/) and still allows the static files to filter through?

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• How to create a generic C free function .

  - by nomemory

  I have some C structures related to a 'list' data structure. They look like this. struct nmlist_element_s { void *data; struct nmlist_element_s *next; }; typedef struct nmlist_element_s nmlist_element; struct nmlist_s { void (*destructor)(void *data); int (*cmp)(const void *e1, const void *e2); unsigned int size; nmlist_element *head; nmlist_element *tail; }; typedef struct nmlist_s nmlist; This way I can have different data types being hold in "nmlist_element-data" . The "constructor" (in terms of OOP) has the following signature: nmlist *nmlist_alloc(void (*destructor)(void *data)); Where "destructor" is specific function that de-allocated "data" (being hold by the nmlist_element). If I want to have a list containing integers as data, my "destructor" would like this: void int_destructor(void *data) { free((int*)data); } Still i find it rather "unfriendly" for me to write a destructor functions for every simple primitive data type. So is there a trick to write something like this ? (for primitives): void "x"_destructor(void *data, "x") { free(("x" *)data); } PS: I am not a macro fan myself, and in my short experience regarding C, i don't use them, unless necessary.

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