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• Spring Integration 1.0 RC2: Streaming file content?

  - by gdm

  I've been trying to find information on this, but due to the immaturity of the Spring Integration framework I haven't had much luck. Here is my desired work flow: New files are placed in an 'Incoming' directory Files are picked up using a file:inbound-channel-adapter The file content is streamed, N lines at a time, to a 'Stage 1' channel, which parses the line into an intermediary (shared) representation. This parsed line is routed to multiple 'Stage 2' channels. Each 'Stage 2' channel does its own processing on the N available lines to convert them to a final representation. This channel must have a queue which ensures no Stage 2 channel is overwhelmed in the event that one channel processes significantly slower than the others. The final representation of the N lines is written to a file. There will be as many output files as there were routing destinations in step 4. *'N' above stands for any reasonable number of lines to read at a time, from [1, whatever I can fit into memory reasonably], but is guaranteed to always be less than the number of lines in the full file. How can I accomplish streaming (steps 3, 4, 5) in Spring Integration? It's fairly easy to do without streaming the files, but my files are large enough that I cannot read the entire file into memory. As a side note, I have a working implementation of this work flow without Spring Integration, but since we're using Spring Integration in other places in our project, I'd like to try it here to see how it performs and how the resulting code compares for length and clarity.

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• Plotting an Arc in Discrete Steps

  - by phobos51594

  Good afternoon, Background My question relates to the plotting of an arbitrary arc in space using discrete steps. It is unique, however, in that I am not drawing to a canvas in the typical sense. The firmware I am designing is for a gcode interpreter for a CNC mill that will translate commands into stepper motor movements. Now, I have already found a similar question on this very site, but the methodology suggested (Bresenham's Algorithm) appears to be incompatable for moving an object in space, as it only relies on the calculation of one octant of a circle which is then mirrored about the remaining axes of symmetry. Furthermore, the prescribed method of calculation an arc between two arbitrary angles relies on trigonometry (I am implementing on a microcontroller and would like to avoid costly trig functions, if possible) and simply not taking the steps that are out of the range. Finally, the algorithm only is designed to work in one rotational direction (e.g. counterclockwise). Question So, on to the actual question: Does anyone know of a general-purpose algorithm that can be used to "draw" an arbitrary arc in discrete steps while still giving respect to angular direction (CW / CCW)? The final implementation will be done in C, but the language for the purpose of the question is irrelevant. Thank you in advance. References S.O post on drawing a simple circle using Bresenham's Algorithm: "Drawing" an arc in discrete x-y steps Wiki page describing Bresenham's Algorithm for a circle http://en.wikipedia.org/wiki/Midpoint_circle_algorithm Gcode instructions to be implemented (see. G2 and G3) http://linuxcnc.org/docs/html/gcode.html

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• Delaying LINQ to SQL Select Query Execution

  - by Maxim Z.

  I'm building an ASP.NET MVC site that uses LINQ to SQL. In my search method that has some required and some optional parameters, I want to build a LINQ query while testing for the existence of those optional parameters. Here's what I'm currently thinking: using(var db = new DBDataContext()) { IQueryable<Listing> query = null; //Handle required parameter query = db.Listings.Where(l => l.Lat >= form.bounds.extent1.latitude && l.Lat <= form.bounds.extent2.latitude); //Handle optional parameter if (numStars != null) query = query.Where(l => l.Stars == (int)numStars); //Other parameters... //Execute query (does this happen here?) var result = query.ToList(); //Process query... Will this implementation "bundle" the where clauses and then execute the bundled query? If not, how should I implement this feature? Also, is there anything else that I can improve? Thanks in advance.

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• On Render Callback For G+ Button

  - by Michael Robinson

  How might I go about performing an action only when a G+ button has finished rendering? Facebook allows one to do this using the following: FB.XFBML.parse(document, function() { alert('rendering done'); }); I've perused Google's documentation, but didn't see anything helpful. Currently my workaround is to monitor the G+ element until certain elements have been added, then perform my action: (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; po.onload = function() { var awaitRender = function(element) { if (element.firstChild && element.firstChild.firstChild && element.firstChild.firstChild.tagName.toUpperCase() === 'IFRAME') { alert('rendered!'); } else { window.setTimeout(function() { awaitRender(element) }, 100); } }; var buttons = document.getElementsByClassName('googleplus-button'); for(var i = 0; i < buttons.length; i++) { awaitRender(buttons[i]); } } var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })(); I'd like to know please, if there is either: A correct way one should do this for G+ buttons A better implementation that what I've hacked together above

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• How to easily map c++ enums to strings

  - by Roddy

  I have a bunch of enum types in some library header files that I'm using, and I want to have a way of converting enum values to user strings - and vice-versa. RTTI won't do it for me, because the 'user strings' need to be a bit more readable than the enumerations. A brute force solution would be a bunch of functions like this, but I feel that's a bit too C-like. enum MyEnum {VAL1, VAL2,VAL3}; String getStringFromEnum(MyEnum e) { switch e { case VAL1: return "Value 1"; case VAL2: return "Value 2"; case VAL1: return "Value 3"; default: throw Exception("Bad MyEnum"); } } I have a gut feeling that there's an elegant solution using templates, but I can't quite get my head round it yet. UPDATE: Thanks for suggestions - I should have made clear that the enums are defined in a third-party library header, so I don't want to have to change the definition of them. My gut feeling now is to avoid templates and do something like this: char * MyGetValue(int v, char *tmp); // implementation is trivial #define ENUM_MAP(type, strings) char * getStringValue(const type &T) \ { \ return MyGetValue((int)T, strings); \ } ; enum eee {AA,BB,CC}; - exists in library header file ; enum fff {DD,GG,HH}; ENUM_MAP(eee,"AA|BB|CC") ENUM_MAP(fff,"DD|GG|HH") // To use... eee e; fff f; std::cout<< getStringValue(e); std::cout<< getStringValue(f);

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• Best approach for Java/Maven/JPA/Hibernate build with multiple database vendor support?

  - by HDave

  I have an enterprise application that uses a single database, but the application needs to support mysql, oracle, and sql*server as installation options. To try to remain portable we are using JPA annotations with Hibernate as the implementation. We also have a test-bed instance of each database running for development. The app is building nicely in Maven, and I've played around with the hibernate3-maven-plugin and can auto-generate DDL for a given database dialect. What is the best way to approach this so that individual developers can easily test against all three databases and our Hudson based CI server can build things propertly. More specifically: 1) I thought the hbm2ddl goal in the hibernate3-maven-plugin would just generate a schema file, but apparently it connects to a live database and attempts to create the schema. Is there a way to have this just create the schema file for each database dialect without connecting to a database? 2) If the hibernate3-maven-plug insists on actually creating the database schema, is there a way to have it drop the database and recreate it before creating the schema? 3) I am thinking that each developer (and the hudson build machine) should have their own separate database on each database server. Is this typical? 4) Will developers have to run Maven three times...once for each database vendor? If so, how do I merge the results on the build machine? 5) There is a hbm2doc goal within hibernate3-maven-plugin. It seems overkill to run this three times...I gotta believe it'd be nearly identical for each database.

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• ObjC internals. Why my duck typing attempt failed?

  - by Piotr Czapla

  I've tried to use id to create duck typing in objective-c. The concept looks fine in theory but failed in practice. I was unable to use any parameters in my methods. The methods were called but parameters were wrong. I was getting BAD_ACESS for objects and random values for primitives. I've attached a simple example below. The question: Does any one knows why the methods parameters are wrong? What is happening under the hood of the objective-c? Note: I'm interest in the details. I know how to make the example below work. An example: I've created a simple class Test that is passed to an other class using property id test. @implementation Test - (void) aSampleMethodWithFloat:(float) f andInt: (int) i { NSLog(@"Parameters: %f, %i\n", f, i); } @end Then in the class the following loop is executed: for (float f=0.0f; f < 100.0f ; f += 0.3f) { [self.test aSampleMethodWithOneFloatParameter: f]; // warning: no method found. } Here is the output that I'm getting. As you can see the method was called but the parameters were wrong. Parameters: 0.000000, 0 Parameters: -0.000000, 1069128089 Parameters: -0.000000, 1070176665 Parameters: 2.000000, 1070805811 Parameters: -0.000000, 1071225241 Parameters: 0.000000, 1071644672 Parameters: 2.000000, 1071854387 Parameters: 36893488147419103232.000000, 1072064102 Parameters: -0.000000, 1072273817 Parameters: -36893488147419103232.000000, 1072483532

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• LINQ-SQL Updating Multiple Rows in a single transaction

  - by RPM1984

  Hi guys, I need help re-factoring this legacy LINQ-SQL code which is generating around 100 update statements. I'll keep playing around with the best solution, but would appreciate some ideas/past experience with this issue. Here's my code: List<Foo> foos; int userId = 123; using (DataClassesDataContext db = new FooDatabase()) { foos = (from f in db.FooBars where f.UserId = userId select f).ToList(); foreach (FooBar fooBar in foos) { fooBar.IsFoo = false; } db.SubmitChanges() } Essentially i want to update the IsFoo field to false for all records that have a particular UserId value. Whats happening is the .ToList() is firing off a query to get all the FooBars for a particular user, then for each Foo object, its executing an UPDATE statement updating the IsFoo property. Can the above code be re-factored to one single UPDATE statement? Ideally, the only SQL i want fired is the below: UPDATE FooBars SET IsFoo = FALSE WHERE UserId = 123 EDIT Ok so looks like it cant be done without using db.ExecuteCommand. Grr...! What i'll probably end up doing is creating another extension method for the DLINQ namespace. Still require some hardcoding (ie writing "WHERE" and "UPDATE"), but at least it hides most of the implementation details away from the actual LINQ query syntax.

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• Should a developer be a coauthor to a paper presented about the application they developed?

  - by ved

  In our organization, project teams come up with a need and funding and developers are given a basic scope and are allowed to develop the solution. There is a certain degree of implementation freedom given to the developers. They drive the solution to pilot and live deployment from its inception. If the solution is presented in a conference as a technical paper/white paper what is the protocol for the list of authors: because for the most part I see the project manager's and the dev team manager's names as authors but no mention of the actual developer. Is this correct? A lot of us developers feel pretty bummed to never see our names as the coauthors. Appreciate any pointers. Answers to the FOLLOW UP questions (1) in what field of study is the paper, and what are the standards of authorship for that field? The paper is for Flood Plain Management - there is nothing on the abstract guidelines, I have called the contact person listed for comment - waiting to hear. 2) was the paper literally about the software application as your question implies, or were the software issues incidental to the topic of the paper? The paper specifically deals with a GIS Application that is used in Coastal Engineering, yes the software is not incidental, but the meat of the paper and mentioned in the Title. 2

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• Iterate through every node in a XML

  - by Rachel

  Hi I am trying to iterate through every node in a xml, be it the element node, text node or comment. With the below XSL in the very first statement prints the complete xml. How do i copy the very first node in $nodes and call the template process-nodes again removing teh first node in my next iteration? <?xml version='1.0'?> <xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <xsl:call-template name="process-nodes"> <xsl:with-param name="nodes" select="//node()" as="node()*"/> </xsl:call-template> </xsl:template> <xsl:template name="process-nodes"> <xsl:param name="nodes" as="node()*" /> <xsl:copy-of select="$nodes[1]"/> <xsl:if test="$nodes"> <xsl:call-template name="process-nodes"> <xsl:with-param name="nodes" select="remove($nodes, 1)" /> </xsl:call-template> </xsl:if> </xsl:template> </xsl:stylesheet> Note: I am looking for fixing the issue in this kind of implementation rather than changing the template match to <xsl:template match="@* | node()"> as I need to have some processing which requires this approach. Thanks.

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• RhinoMocks: how to test if method was called when using PartialMock

  - by epitka

  I have a clas that is something like this public class MyClass { public virtual string MethodA(Command cmd) { //some code here} public void MethodB(SomeType obj) { // do some work MethodA(command); } } I mocked MyClass as PartialMock (mocks.PartialMock<MyClass>) and I setup expectation for MethodA var cmd = new Command(); //set the cmd to expected state Expect.Call(MyClass.MethodA(cmd)).Repeat.Once(); Problem is that MethodB calls actual implementation of MethodA instead of mocking it up. I must be doing something wrong (not very experienced with RhinoMocks). How do I force it to mock MetdhodA? Here is the actual code: var cmd = new SetBaseProductCoInsuranceCommand(); cmd.BaseProduct = planBaseProduct; var insuredType = mocks.DynamicMock<InsuredType>(); Expect.Call(insuredType.Code).Return(InsuredTypeCode.AllInsureds); cmd.Values.Add(new SetBaseProductCoInsuranceCommand.CoInsuranceValues() { CoInsurancePercent = 0, InsuredType = insuredType, PolicySupplierType = ppProvider }); Expect.Call(() => service.SetCoInsurancePercentages(cmd)).Repeat.Once(); mocks.ReplayAll(); //act service.DefaultCoInsurancesFor(planBaseProduct); //assert service.AssertWasCalled(x => x.SetCoInsurancePercentages(cmd),x=>x.Repeat.Once());

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• Why does this program take up so much memory?

  - by Adrian

  I am learning Objective-C. I am trying to release all of the memory that I use. So, I wrote a program to test if I am doing it right: #import <Foundation/Foundation.h> #define DEFAULT_NAME @"Unknown" @interface Person : NSObject { NSString *name; } @property (copy) NSString * name; @end @implementation Person @synthesize name; - (void) dealloc { [name release]; [super dealloc]; } - (id) init { if (self = [super init]) { name = DEFAULT_NAME; } return self; } @end int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; Person *person = [[Person alloc] init]; NSString *str; int i; for (i = 0; i < 1e9; i++) { str = [NSString stringWithCString: "Name" encoding: NSUTF8StringEncoding]; person.name = str; [str release]; } [person release]; [pool drain]; return 0; } I am using a mac with snow leopard. To test how much memory this is using, I open Activity Monitor at the same time that it is running. After a couple of seconds, it is using gigabytes of memory. What can I do to make it not use so much?

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• Java Concurrency in practice sample question

  - by andy boot

  I am reading "Java Concurrency in practice" and looking at the example code on page 51. This states that if a thread has references to a shared object then other threads may be able to access that object before the constructor has finished executing. I have tried to put this into practice and so I wrote this code thinking that if I ran it enough times a RuntimeException("World is f*cked") would occur. But it isn't doing. Is this a case of the Java spec not guaranting something but my particular implementation of java guaranteeing it for me? (java version: 1.5.0 on Ubuntu) Or have I misread something in the book? Code: (I expect an exception but it is never thrown) public class Threads { private Widgit w; public static void main(String[] s) throws Exception { while(true){ Threads t = new Threads(); t.runThreads(); } } private void runThreads() throws Exception{ new Checker().start(); w = new Widgit((int)(Math.random() * 100) + 1); } private class Checker extends Thread{ private static final int LOOP_TIMES = 1000; public void run() { int count = 0; for(int i = 0; i < LOOP_TIMES; i++){ try { w.checkMe(); count++; } catch(NullPointerException npe){ //ignore } } System.out.println("checked: "+count+" times out of "+LOOP_TIMES); } } private static class Widgit{ private int n; private int n2; Widgit(int n) throws InterruptedException{ this.n = n; Thread.sleep(2); this.n2 = n; } void checkMe(){ if (n != n2) { throw new RuntimeException("World is f*cked"); } } } }

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• Most Elegant Way to write isPrime in java

  - by Anantha Kumaran

  public class Prime { public static boolean isPrime1(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } for (int i = 2; i <= Math.sqrt(n) + 1; i++) { if (n % i == 0) { return false; } } return true; } public static boolean isPrime2(int n) { if (n <= 1) { return false; } if (n == 2) { return true; } if (n % 2 == 0) { return false; } for (int i = 3; i <= Math.sqrt(n) + 1; i = i + 2) { if (n % i == 0) { return false; } } return true; } } public class PrimeTest { public PrimeTest() { } @Test public void testIsPrime() throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { Prime prime = new Prime(); TreeMap<Long, String> methodMap = new TreeMap<Long, String>(); for (Method method : Prime.class.getDeclaredMethods()) { long startTime = System.currentTimeMillis(); int primeCount = 0; for (int i = 0; i < 1000000; i++) { if ((Boolean) method.invoke(prime, i)) { primeCount++; } } long endTime = System.currentTimeMillis(); Assert.assertEquals(method.getName() + " failed ", 78498, primeCount); methodMap.put(endTime - startTime, method.getName()); } for (Entry<Long, String> entry : methodMap.entrySet()) { System.out.println(entry.getValue() + " " + entry.getKey() + " Milli seconds "); } } } I am trying to find the fastest way to check whether the given number is prime or not. This is what is finally came up with. Is there any better way than the second implementation(isPrime2).

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• java.math.BigInteger pow(exponent) question

  - by Jan Kraus

  Hi, I did some tests on pow(exponent) method. Unfortunately, my math skills are not strong enough to handle the following problem. I'm using this code: BigInteger.valueOf(2).pow(var); Results: var | time in ms 2000000 | 11450 2500000 | 12471 3000000 | 22379 3500000 | 32147 4000000 | 46270 4500000 | 31459 5000000 | 49922 See? 2,500,000 exponent is calculated almost as fast as 2,000,000. 4,500,000 is calculated much faster then 4,000,000. Why is that? To give you some help, here's the original implementation of BigInteger.pow(exponent): public BigInteger pow(int exponent) { if (exponent < 0) throw new ArithmeticException("Negative exponent"); if (signum==0) return (exponent==0 ? ONE : this); // Perform exponentiation using repeated squaring trick int newSign = (signum<0 && (exponent&1)==1 ? -1 : 1); int[] baseToPow2 = this.mag; int[] result = {1}; while (exponent != 0) { if ((exponent & 1)==1) { result = multiplyToLen(result, result.length, baseToPow2, baseToPow2.length, null); result = trustedStripLeadingZeroInts(result); } if ((exponent >>>= 1) != 0) { baseToPow2 = squareToLen(baseToPow2, baseToPow2.length, null); baseToPow2 = trustedStripLeadingZeroInts(baseToPow2); } } return new BigInteger(result, newSign); }

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• Java ternary operator and boxing Integer/int?

  - by Markus

  I tripped across a really strange NullPointerException the other day caused by an unexpected type-cast in the ternary operator. Given this (useless exemplary) function: Integer getNumber() { return null; } I was expecting the following two code segments to be exactly identical after compilation: Integer number; if (condition) { number = getNumber(); } else { number = 0; } vs. Integer number = (condition) ? getNumber() : 0; . Turns out, if condition is true, the if-statement works fine, while the ternary opration in the second code segment throws a NullPointerException. It seems as though the ternary operation has decided to type-cast both choices to int before auto-boxing the result back into an Integer!?! In fact, if I explicitly cast the 0 to Integer, the exception goes away. In other words: Integer number = (condition) ? getNumber() : 0; is not the same as: Integer number = (condition) ? getNumber() : (Integer) 0; . So, it seems that there is a byte-code difference between the ternary operator and an equivalent if-else-statement (something I didn't expect). Which raises three questions: Why is there a difference? Is this a bug in the ternary implementation or is there a reason for the type cast? Given there is a difference, is the ternary operation more or less performant than an equivalent if-statement (I know, the difference can't be huge, but still)?

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• App Crashes Loading View Controllers

  - by golfromeo

  I have the following code in my AppDelegate.h file: @class mainViewController; @class AboutViewController; @interface iSearchAppDelegate : NSObject <UIApplicationDelegate> { UIWindow *window; mainViewController *viewController; AboutViewController *aboutController; UINavigationController *nav; } @property (nonatomic, retain) IBOutlet UIWindow *window; @property (nonatomic, retain) IBOutlet mainViewController *viewController; @property (nonatomic, retain) IBOutlet AboutViewController *aboutController; @property (nonatomic, retain) IBOutlet UINavigationController *nav; [...IBActions declared here...] @end Then, in my .m file: @implementation iSearchAppDelegate @synthesize window; @synthesize viewController, aboutController, settingsData, nav, engines; (void)applicationDidFinishLaunching:(UIApplication *)application { [window addSubview:nav.view]; [window addSubview:aboutController.view]; [window addSubview:viewController.view]; [window makeKeyAndVisible]; } -(IBAction)switchToHome{ [window bringSubviewToFront:viewController.view]; } -(IBAction)switchToSettings{ [window bringSubviewToFront:nav.view]; } -(IBAction)switchToAbout{ [window bringSubviewToFront:aboutController.view]; } - (void)dealloc { [viewController release]; [aboutController release]; [nav release]; [window release]; [super dealloc]; } @end Somehow, when I run the app, the main view presents itself fine... however, when I try to execute the actions to switch views, the app crashes with an EXC_BAD_ACCESS. Thanks for any help in advance.

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• What hash algorithms are paralellizable? Optimizing the hashing of large files utilizing on mult-co

  - by DanO

  I'm interested in optimizing the hashing of some large files (optimizing wall clock time). The I/O has been optimized well enough already and the I/O device (local SSD) is only tapped at about 25% of capacity, while one of the CPU cores is completely maxed-out. I have more cores available, and in the future will likely have even more cores. So far I've only been able to tap into more cores if I happen to need multiple hashes of the same file, say an MD5 AND a SHA256 at the same time. I can use the same I/O stream to feed two or more hash algorithms, and I get the faster algorithms done for free (as far as wall clock time). As I understand most hash algorithms, each new bit changes the entire result, and it is inherently challenging/impossible to do in parallel. Are any of the mainstream hash algorithms parallelizable? Are there any non-mainstream hashes that are parallelizable (and that have at least a sample implementation available)? As future CPUs will trend toward more cores and a leveling off in clock speed, is there any way to improve the performance of file hashing? (other than liquid nitrogen cooled overclocking?) or is it inherently non-parallelizable?

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• Communicating with all network computers regardless of IP address

  - by Stephen Jennings

  I'm interested in finding a way to enumerate all accessible devices on the local network, regardless of their IP address. For example, in a 192.168.1.X network, if there is a computer with a 10.0.0.X IP address plugged into the network, I want to be able to detect that rogue computer and preferrably communicate with it as well. Both computers will be running this custom software. I realize that's a vague description, and a full solution to the problem would be lengthy, so I'm really looking for help finding the right direction to go in ("Look into using class XYZ and ABC in this manner") rather than a full implementation. The reason I want this is that our company ships imaged computers to thousands of customers, each of which have different network settings (most use the same IP scheme, but a large percentage do not, and most do not have DHCP enabled on their networks). Once the hardware arrives, we have a hard time getting it up on the network, especially if the IP scheme doesn't match, since there is no one technically oriented on-site. Ideally, I want to design some kind of console to be used from their main workstation which looks out on the network, finds all computers running our software, displays their current IP address, and allows you to change the IP. I know it's possible to do this because we sell a couple pieces of custom hardware which have exactly this capability (plug the hardware in anywhere and view it from another computer regardless of IP), but I'm hoping it's possible to do in .NET 2.0, but I'm open to using .NET 3.5 or P/Invoke if I have to.

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• Endianness and C API's: Specifically OpenSSL.

  - by Hassan Syed

  I have an algorithm that uses the following OpenSSL calls: HMAC_update() / HMAC_final() // ripe160 EVP_CipherUpdate() / EVP_CipherFinal() // cbc_blowfish These algorithm take a unsigned char * into the "plain text". My input data is comes from a C++ std::string::c_str() which originate from a protocol buffer object as a encoded UTF-8 string. UTF-8 strings are meant to be endian neutrial. However I'm a bit paranoid about how OpenSSL may perform operations on the data. My understanding is that encryption algorithms work on 8-bit blocks of data, and if a unsigned char * is used for pointer arithmetic when the operations are performed the algorithms should be endian neutral and I do not need to worry about anything. My uncertainty is compounded by the fact that I am working on a little-endian machine and have never done any real cross-architecture programming. My beliefs/reasoning are/is based on the following two properties std::string (not wstring) internally uses a 8-bit ptr and a the resulting c_str() ptr will itterate the same way regardless of the CPU architecture. Encryption algorithms are either by design, or by implementation, endian neutral. I know the best way to get a definitive answer is to use QEMU and do some cross-platform unit tests (which I plan to do). My question is a request for comments on my reasoning, and perhaps will assist other programmers when faced with similar problems.

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• MVC2 Modelbinder for List of derived objects

  - by user250773

  I want a list of different (derived) object types working with the Default Modelbinder in Asp.net MVC 2. I have the following ViewModel: public class ItemFormModel { [Required(ErrorMessage = "Required Field")] public string Name { get; set; } public string Description { get; set; } [ScaffoldColumn(true)] //public List<Core.Object> Objects { get; set; } public ArrayList Objects { get; set; } } And the list contains objects of diffent derived types, e.g. public class TextObject : Core.Object { public string Text { get; set; } } public class BoolObject : Core.Object { public bool Value { get; set; } } It doesn't matter if I use the List or the ArrayList implementation, everything get's nicely scaffolded in the form, but the modelbinder doesn't resolve the derived object type properties for me when posting back to the ActionResult. What could be a good solution for the Viewmodel structure to get a list of different object types handled? Having an extra list for every object type (e.g. List, List etc.) seems to be not a good solution for me, since this is a lot of overhead both in building the viewmodel and mapping it back to the domain model. Thinking about the other approach of binding all properties in a custom model binder, how can I make use the data annotations approach here (validating required attributes etc.) without a lot of overhead?

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• Problem with circular definition in Scheme

  - by user8472

  I am currently working through SICP using Guile as my primary language for the exercises. I have found a strange behavior while implementing the exercises in chapter 3.5. I have reproduced this behavior using Guile 1.4, Guile 1.8.6 and Guile 1.8.7 on a variety of platforms and am certain it is not specific to my setup. This code works fine (and computes e): (define y (integral (delay dy) 1 0.001)) (define dy (stream-map (lambda (x) x) y)) (stream-ref y 1000) The following code should give an identical result: (define (solve f y0 dt) (define y (integral (delay dy) y0 dt)) (define dy (stream-map f y)) y) (solve (lambda (x) x) 1 0.001) But it yields the error message: standard input:7:14: While evaluating arguments to stream-map in expression (stream-map f y): standard input:7:14: Unbound variable: y ABORT: (unbound-variable) So when embedded in a procedure definition, the (define y ...) does not work, whereas outside the procedure in the global environment at the REPL it works fine. What am I doing wrong here? I can post the auxiliary code (i.e., the definitions of integral, stream-map etc.) if necessary, too. With the exception of the system-dependent code for cons-stream, they are all in the book. My own implementation of cons-stream for Guile is as follows: (define-macro (cons-stream a b) `(cons ,a (delay ,b)))

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• How does one implement storage/retrieval of smart-search/mailbox features?

  - by humble_coder

  Hi All, I have a question regarding implementation of smart-search features. For example, consider something like "smart mailboxes" in various email applications. Let's assume you have your data (emails) stored in a database and, depending on the field for which the query will be created, you present different options to the end user. At the moment let's assume the Subject, Verb, Object approach… For instance, say you have the following: SUBJECTs: message, to_address, from_address, subject, date_received VERBs: contains, does_not_contain, is_equal_to, greater_than, less_than OBJECTs: ??????? Now, in case it isn't clear, I want a table structure (although I'm not opposed to an external XMLesque file of some sort) to store (and later retrieve/present) my criteria for smart searches/mailboxes for later use. As an example, using SVO I could easily store then reconstruct a query for "date between two dates" -- simply use "date greater than" AND "date less than". However, what if, in the same smart search, I wanted a "between" OR'ed with another criterion? You can see that it might get out of hand -- not necessarily in the query creation (as that is rather simplistic), but in the option presentation and storage mechanism. Perhaps I need to think more on a more granular level. Perhaps I need to simply allow the user to select AND or OR for each entry independently instead of making it an ALL OR NOTHING type smart search (i.e. instead of MATCH ALL or MATCH ANY, I need to simply allow them to select -- I just don't want it to turn into a Hydra). Any input would be most appreciated. My apologies if the question is a bit incoherent. It is late, and I my brain is toast. Best.

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• Performance of C# method polymorphism with generics

  - by zildjohn01

  I noticed in C#, unlike C++, you can combine virtual and generic methods. For example: using System.Diagnostics; class Base { public virtual void Concrete() {Debug.WriteLine("base concrete");} public virtual void Generic<T>() {Debug.WriteLine("base generic");} } class Derived : Base { public override void Concrete() {Debug.WriteLine("derived concrete");} public override void Generic<T>() {Debug.WriteLine("derived generic");} } class App { static void Main() { Base x = new Derived(); x.Concrete(); x.Generic<PerformanceCounter>(); } } Given that any number of versions of Generic<T> could be instantiated, it doesn't look like the standard vtbl approach could be used to resolve method calls, and in fact it's not. Here's the generated code: x.Concrete(); mov ecx,dword ptr [ebp-8] mov eax,dword ptr [ecx] call dword ptr [eax+38h] x.Generic<PerformanceCounter>(); push 989A38h mov ecx,dword ptr [ebp-8] mov edx,989914h call 76A874F1 mov dword ptr [ebp-4],eax mov ecx,dword ptr [ebp-8] call dword ptr [ebp-4] The extra code appears to be looking up a dynamic vtbl according to the generic parameters, and then calling into it. Has anyone written about the specifics of this implementation? How well does it perform compared to the non-generic case?

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• Fastest XML parser for small, simple documents in Java

  - by Varkhan

  I have to objectify very simple and small XML documents (less than 1k, and it's almost SGML: no namespaces, plain UTF-8, you name it...), read from a stream, in Java. I am using JAXP to process the data from my stream into a Document object. I have tried Xerces, it's way too big and slow... I am using Dom4j, but I am still spending way too much time in org.dom4j.io.SAXReader. Does anybody out there have any suggestion on a faster, more efficient implementation, keeping in mind I have very tough CPU and memory constraints? [Edit 1] Keep in mind that my documents are very small, so the overhead of staring the parser can be important. For instance I am spending as much time in org.xml.sax.helpers.XMLReaderFactory.createXMLReader as in org.dom4j.io.SAXReader.read [Edit 2] The result has to be in Dom format, as I pass the document to decision tools that do arbitrary processing on it, like switching code based on the value of arbitrary XPaths, but also extracting lists of values packed as children of a predefined node. [Edit 3] In any case I eventually need to load/parse the complete document, since all the information it contains is going to be used at some point. (This question is related to, but different from, http://stackoverflow.com/questions/373833/best-xml-parser-for-java )

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