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• Makefile trickery using VPATH and include.

  - by roe

  Hi, I'm playing around with make files and the VPATH variable. Basically, I'm grabbing source files from a few different places (specified by the VPATH), and compile them into the current directory using simply a list of .o-files that I want. So far so good, now I'm generating dependency information into a file called '.depend' and including that. Gnumake will attempt to use the rules defined so far to create the included file if it doesn't exist, so that's ok. Basically, my makefile looks like this. VPATH=A/source:B/source:C/source objects=first.o second.o third.o executable: $(objects) .depend: $(objects:.o=.c) $(CC) -MM $^ > $@ include .depend Now for the real question, can I suppress the generation of the .depend file in any way? I'm currently working in a clearcase environment - sloooow, so I'd prefer to have it a bit more under control when to update the dependency information. It's more or less an academic exercise as I could just wrap the thing in a script which is touching the .depend file before executing make (thus making it more recent than any source file), but it'd interesting to know if I can somehow suppress it using 'pure' make. I cannot remove the dependency to the source files (i.e. using simply .depend:), as I'm depending on the $^ variable to do the VPATH resolution for me. If there'd be any way to only update dependencies as a result of updated #include directives, that'd be even better of course.. But I'm not holding my breath for that one.. :)

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• Is it valid to use unsafe struct * as an opaque type instead of IntPtr in .NET Platform Invoke?

  - by David Jeske

  .NET Platform Invoke advocates declaring pointer types as IntPtr. For example, the following [DllImport("user32.dll")] static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, Int32 wParam, Int32 lParam); However, I find when interfacing with interesting native interfaces, that have many pointer types, flattening everything into IntPtr makes the code very hard to read and removes the typical typechecking that a compiler can do. I've been using a pattern where I declare an unsafe struct to be an opaque pointer type. I can store this pointer type in a managed object, and the compiler can typecheck it form me. For example: class Foo { unsafe struct FOO {}; // opaque type unsafe FOO *my_foo; class if { [DllImport("mydll")] extern static unsafe FOO* get_foo(); [DllImport("mydll")] extern static unsafe void do_something_foo(FOO *foo); } public unsafe Foo() { this.my_foo = if.get_foo(); } public unsafe do_something_foo() { if.do_something_foo(this.my_foo); } While this example may not seem different than using IntPtr, when there are several pointer types moving between managed and native code, using these opaque pointer types for typechecking is a godsend. I have not run into any trouble using this technique in practice. However, I also have not seen an examples of anyone using this technique, and I wonder why. Is there any reason that the above code is invalid in the eyes of the .NET runtime? My main question is about how the .NET GC system treats "unsafe FOO *my_foo". Is this pointer something the GC system is going to try to trace, or is it simply going to ignore it? My hope is that because the underlying type is a struct, and it's declared unsafe, that the GC would ignore it. However, I don't know for sure. Thoughts?

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• Programming test for ASP.NET C# developer job - Opinions please!

  - by Indy

  Hi all, We are hiring a .NET C# developer and I have developed a technical test for the candidates to complete. They have an hour and it has two parts, some knowledge based questions covering asp.net, C# and SQL and a small practical test. I'd appreciate feedback on the test, is it sufficient to test the programmers ability? What would you change if anything? Part One. What the are events fired as part of the ASP.NET Page lifecycle. What interesting things can you do at each? How does ViewState work and why is it either useful or bad? What is a common way to create web services in ASP.NET 2.0? What is the GAC? What is boxing? What is a delegate? The C# keyword .int. maps to which .NET type? Explain the difference between a Stored Procedure and a Trigger? What is an OUTER Join? What is @@IDENTITY? Part Two: You are provided with the Northwind Database and the attached DB relationship diagram. Please create a page which provides users with the following functionality. You don’t need to be too concerned with the presentation detail of the page. Select a customer from a list, and see all the orders placed by that customer. For the same customer, find all their orders which are Beverages and the quantity is more than 5. I was aware of setting the right balance of difficulty on this as there is an hour's test. I was able to complete the practical test in under 30 mins using SQLDatasource and the query designer in visual studio and the test questions, I am looking to see how they approach it logically and whether they use the tools available. Many thanks!

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• Best architecture for a social media app

  - by Sky

  Hey guys, Im working on promising project that develops a new social media app for web and mobile. We are at begin defining functionalities. Nevertheless, I'm thinking ahead on architecture. So I'm asking: 1 - Whats the best plataform to develop the core of this aplication that will have a Rest API interface. 2 - Whats the best database that will scale and grow with my application. As far as I researched, these were the answers I found most interesting: For database: Cassandra NoSQL DB, amazing scalabilty, amazing write performance, good read performance (will be improved on 0.6). I think i will choose that one. Zookeer for transactions on Cassandra. I think that 2 technologies rly good for that propose. What do you think guys? On the front end that will serve the REST API, i dont have a final candidate. For this one i have questions based on Perfomance X Scalabilty X Fast Development/Maintenance. Java or .Net As far as I researched, brings the best balance of this requisits. Python, pearl and Rail, has the best (Fast Development/Maintenance), but sux on all other. C or C++ I dont even consider, because its (Fast Development/Maintenance) sux... So what do you guy think about it?

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• kick off a map reduce job from my java/mysql webapp

  - by Brian

  Hi guys, I need a bit of archecture advice. I have a java based webapp, with a JPA based ORM backed onto a mysql relational database. Now, as part of the application I have a batch job that compares thousands of database records with each other. This job has become too time consuming and needs to be parallelized. I'm looking at using mapreduce and hadoop in order to do this. However, I'm not too sure about how to integrate this into my current architecture. I think the easiest initial solution is to find a way to push data from mysql into hadoop jobs. I have done some initial research on this and found the following relevant information and possibilities: 1) https://issues.apache.org/jira/browse/HADOOP-2536 this gives an interesting overview of some inbuilt JDBC support 2) This article http://architects.dzone.com/articles/tools-moving-sql-database describes some third party tools to move data from mysql to hadoop. To be honest I'm just starting out with learning about hbase and hadoop but I really don't know how to integrate this into my webapp. Any advice is greatly appreciated. cheers, Brian

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• How would I make a mouse controlled physics object in Box2D / AS3?

  - by Marty Wallace

  I recently created this tennis game using my own basic physics: http://martywallace.com/sandbox/tennis/ Basically a tennis racquet sticks to your mouse and you can hit the tennis balls upward. The physics aren't that great, and I want to make a more interesting version of this game with milestones and levels in Flash. I am planning to use Box2D because I have moderate experience with it. I'm not sure how to go about creating the racquet - as far as I understand Box2D, the racquet needs a velocity to influence the velocities of the balls when you hit them (so that you can hit them harder or softer upward to keep them up). With that said, I'm assuming I can't just have a kinematic body that will have its position set to the mouse, because it won't affect the velocities of the balls as expected. I've also thought about setting the velocity to the difference between the racquet position and the mouse each frame, but I am concerned that won't provide accurate positioning and am also thinking that the velocity could end up really large if you move the mouse quickly. What is the correct way to have a physics object locked to the mouse but also to have its displacement in the last frame (from where it was to the mouse) affect the balls?

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• notify listener inside or outside inner synchronization

  - by Jary Zeels

  Hello all, I am struggling with a decision. I am writing a thread-safe library/API. Listeners can be registered, so the client is notified when something interesting happens. Which of the two implementations is most common? class MyModule { protected Listener listener; protected void somethingHappens() { synchronized(this) { ... do useful stuff ... listener.notify(); } } } or class MyModule { protected Listener listener; protected void somethingHappens() { Listener l = null; synchronized(this) { ... do useful stuff ... l = listener; } l.notify(); } } In the first implementation, the listener is notified inside the synchronization. In the second implementation, this is done outside the synchronization. I feel that the second one is advised, as it makes less room for potential deadlocks. But I am having trouble to convince myself. A downside of the second imlementation is that the client might receive 'incorrect' notifications, which happens if it accessed the module prior to the l.notify() statement. thanks a lot

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• Understanding Hibernate saveOrUpdate

  - by Stephano

  The books that I've read regarding hibernate are, at best, reference tomes. They very seldom have good code examples, so I tend to use online resources for those needs. However, I've always had a problem understanding the basic idea of hibernate persistence. I've read the books and understand the concepts, but in practice, I often see results that I don't understand. Perhaps you all can help, as you have in the past. Let's look at a simple example of a dog and a cat that are friends. This isn't a rare occurrence. It also has the benefit of being much more interesting than my business case. We want a function called "saveFriends" that takes a dog name and a cat name. We'll save the Dog and then the Cat. For this example to work, the cat is going to have a reference back to the dog. I understand this isn't an ideal example, but it's cute and works for our purposes. FriendService.java public int saveFriends(String dogName, String catName) { Dog fido = new Dog(); Cat felix = new Cat(); fido.name = dogName; fido = animalDao.saveDog(fido); felix.name = catName; [ex.A]felix.friend = fido; [ex.B]felix.friend = animalDao.getDogByName(dogName); animalDao.saveCat(felix); } AnimalDao.java (extends HibernateDaoSupport) public Dog saveDog(Dog dog) { getHibernateTemplate().saveOrUpdate(dog); return dog } public Cat saveCat(Cat cat) { getHibernateTemplate().saveOrUpdate(cat); return cat; } public Dog getDogByName(String name) { return (Dog) getHibernateTemplate().find("from Dog where name=?", name).get(0); } Now, assume for a minute that I would like to use either example A or example B to save my friend. Is one better than the other to use? I'll understand if neither of those examples work, but please explain why.

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• Most efficient way to check for DBNull and then assign to a variable?

  - by ilitirit

  This question comes up occasionally but I haven't seen a satisfactory answer. A typical pattern is (row is a DataRow): if (row["value"] != DBNull.Value) { someObject.Member = row["value"]; } My first question is which is more efficient (I've flipped the condition): row["value"] == DBNull.Value; // Or row["value"] is DBNull; // Or row["value"].GetType() == typeof(DBNull) // Or... any suggestions? This indicates that .GetType() should be faster, but maybe the compiler knows a few tricks I don't? Second question, is it worth caching the value of row["value"] or does the compiler optimize the indexer away anyway? eg. object valueHolder; if (DBNull.Value == (valueHolder = row["value"])) {} Disclaimers: row["value"] exists. I don't know the column index of the column (hence the column name lookup) I'm asking specifically about checking for DBNull and then assignment (not about premature optimization etc). Edit: I benchmarked a few scenarios (time in seconds, 10000000 trials): row["value"] == DBNull.Value: 00:00:01.5478995 row["value"] is DBNull: 00:00:01.6306578 row["value"].GetType() == typeof(DBNull): 00:00:02.0138757 Object.ReferenceEquals has the same performance as "==" The most interesting result? If you mismatch the name of the column by case (eg. "Value" instead of "value", it takes roughly ten times longer (for a string): row["Value"] == DBNull.Value: 00:00:12.2792374 The moral of the story seems to be that if you can't look up a column by it's index, then ensure that the column name you feed to the indexer matches the DataColumn's name exactly. Caching the value also appears to be nearly twice as fast: No Caching: 00:00:03.0996622 With Caching: 00:00:01.5659920 So the most efficient method seems to be: object temp; string variable; if (DBNull.Value != (temp = row["value"]) { variable = temp.ToString(); } This was a good learning experience.

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• What is usefulness of W3C's Semantic Data Extractor in semantically correct XHTML CSS Development?

  - by metal-gear-solid

  What is the usefulness of W3C's Semantic Data Extractor? http://www.w3.org/2003/12/semantic-extractor.html This tool, geared by an XSLT stylesheet, tries to extract some information from a HTML semantic rich document. It only uses information available through a good usage of the semantics defined in HTML. The aim is to show that providing a semantically rich HTML gives much more value to your code: using a semantically rich HTML code allows a better use of CSS, makes your HTML intelligible to a wider range of user agents (especially search engines bots). As an aside, it can give clues to user agents developers on some hooks that could be interesting to add in their product. After checking validation for CSS and HTML. Should i go for Semantic Data Extractor tool. What it does. and how it can improved our coding.? Is anyone using it? And i check some site randomly with but with most of sites it gives error Using org.apache.xerces.parsers.SAXParser Exception net.sf.saxon.trans.XPathException: org.xml.sax.SAXParseException: The element type "input" must be terminated by the matching end-tag "`</input>`". org.xml.sax.SAXParseException: The element type "input" must be terminated by the matching end-tag "`</input>`".

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• What is usefulness of W3C's "Semantic Data Extractor" in semantically correct XHTML CSS Development?

  - by metal-gear-solid

  What is the usefulness of W3C's Semantic Data Extractor? http://www.w3.org/2003/12/semantic-extractor.html This tool, geared by an XSLT stylesheet, tries to extract some information from a HTML semantic rich document. It only uses information available through a good usage of the semantics defined in HTML. The aim is to show that providing a semantically rich HTML gives much more value to your code: using a semantically rich HTML code allows a better use of CSS, makes your HTML intelligible to a wider range of user agents (especially search engines bots). As an aside, it can give clues to user agents developers on some hooks that could be interesting to add in their product. After checking validation for CSS and HTML. Should i go for Semantic Data Extractor tool. What it does. and how it can improved our coding.? Is anyone using it? And i check some site randomly with but with most of sites it gives error Using org.apache.xerces.parsers.SAXParser Exception net.sf.saxon.trans.XPathException: org.xml.sax.SAXParseException: The element type "input" must be terminated by the matching end-tag "`</input>`". org.xml.sax.SAXParseException: The element type "input" must be terminated by the matching end-tag "`</input>`". Is it possible to get pass every site with this tool? on one site i got this error No top-level heading (h1) found, no outline extracted. Is it necessary to have at least a H1 in any webpage?

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• Jquery Ui DatePicker, attaches to textbox but only works once, then all click events are disabled.

  - by RubbleFord

  <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> <link rel="stylesheet" href="css/ui-lightness/jquery-ui-1.7.2.custom.css" type="text/css" media="all" /> <script type="text/javascript" src="js/jquery-1.3.2.min.js"></script> <script type="text/javascript" src="js/jquery-ui-1.7.2.custom.min.js"></script> <script type="text/javascript"> $(document).ready(function() { $('#date').datepicker(); }); </script> </head> <body> <%--<form id="form1" runat="server">--%> <div> <input type="text" id="date" /> </div> <%--</form>--%> </body> </html> I've attached a datepicker to a text box and the first time I click it, it works a treat and populates the text box with the current date. It works fine in IE7 Comp mode, Chrome and Firefox. It works once or twice on IE8 but locks the browser up after that. One interesting note is the host operating system is Windows 2008 R2. Any ideas?

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• Need help in tuning a sql-query

  - by Viper

  Hello, i need some help to boost this SQL-Statement. The execution time is around 125ms. During the runtime of my program this sql (better: equally structured sqls for different tables) will be called 300.000 times. The average row count in the tables lies around 10.000.000 rows and new rows (updates/inserts) will be added with a timestamp each day. Data which are interesting for this particular export-program lies in the last 1-3 days. Maybe this is helpful for an index to create. The data i need is the current valid row for a given id and the forerunner datarow to get the updates (if exists). We use a Oracle 11g database and Dot.Net Framework 3.5 SQL-Statement to boost: select ID_SOMETHING, -- Number(12) ID_CONTRIBUTOR, -- Char(4 Byte) DATE_VALID_FROM, -- DATE DATE_VALID_TO -- DATE from TBL_SOMETHING XID where ID_SOMETHING = :ID_INSTRUMENT and ID_CONTRIBUTOR = :ID_CONTRIBUTOR and DATE_VALID_FROM <= :EXPORT_DATE and DATE_VALID_TO >= :EXPORT_DATE order by DATE_VALID_FROM asc; Here i uploaded the current Explain-Plan for this query. I'm not a database expert so i don't know which index-type would fit best for this requirement. I have seen that there are many different possible index-types which could be applied. Maybe Oracle Optimizer Hints are helpful, too. Does anyone has a good idea for tuning this sql or can point me in a right direction?

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• PDO empy result from SELECT when using AND

  - by Jurgen

  Hello, I've come upon a rather interesting thing, which I can't seem to figure out myself. Everytime when executing a SQL statement which contains a '... AND ...' the result is empty. Example: echo('I have a user: ' . $email . $wachtwoord . '<br>'); $dbh = new PDO($dsn, $user, $password); $sql = 'SELECT * FROM user WHERE email = :email AND wachtwoord= :wachtwoord'; $stmt = $dbh->prepare($sql); $stmt->bindParam(:email,$email,PDO::PARAM_STR); $stmt->bindParam(:wachtwoord,$wachtwoord,PDO::PARAM_STR); $stmt->execute(); while($row = $stmt->fetchObject()) { echo($row-email . ',' . $row-wachtwoord); $user[] = array( 'email' = $row-email, 'wachtwoord' = $row-wachtwoord ); } The first echo displays the correct values, however the line with echo($row->email . ',' . $row->wachtwoord); is never reached. A few things I want to add: 1) I am connected to the database since other queries work, only the ones where I add an 'AND' after my 'WHERE's fail. 2) Working with the while works perfectly with queries that do not contain '... AND ...' 3) Error reporting is on, PDO gives no exceptions on my query (or anything else) 4) Executing the query directly on the database does give what I want: SELECT * FROM user WHERE email = '[email protected]' AND wachtwoord = 'jurgen' I can stare at it all day long again (which I already did once, but I managed to work around the 'AND'), but maybe one of you can give me a helping hand. Thank you in advance. Jurgen

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• Visual Studio 2008 freeze after save

  - by Klay

  I recently added about a dozen classes from another solution into my current solution in Visual Studio. After adding these classes, Visual Studio started freezing for about 10 seconds whenever I Save. The cursor disappears and mouse clicks and keys do nothing. Some interesting points: Even after I removed the classes, the freezing behavior is still there. Freezing occurs whether I've made changes to the code or not. This behavior ONLY seems to affect this particular version of this solution. No other solutions exhibit this behavior. Older versions of this solution are not affected. In Sysinternals Process Explorer, whenever I save in Visual Studio, the I/O bytes graph jumps from 0 to 2MB for about 5 seconds, then drops to about 1 MB for a split second, then jumps back to 2MB for another 5 seconds. Processor use goes up to about 3-5% during this time. Here are the details of my setup: C# Silverlight project (maybe 20 classes), .NET version 3.5 SP1, Visual Studio 2008 v9.0.30729 SP1. EDIT: I edited this question extensively to reflect the more detailed information. I thought this might be preferable to starting a new question.

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• Web Servicet Client in JBOSS 5.1 with JDK6

  - by dcp

  This is a continuation of the question here: http://stackoverflow.com/questions/2435286/jboss-does-app-have-to-be-compiled-under-same-jdk-as-jboss-is-running-under It's different enough though that it required a new question. I am trying to use jdk6 to run JBOSS 5.1, and I downloaded the JDK6 version of JBOSS 5.1. This works fine and my EAR application deploys fine. However, when I want to run a web service client with code like this: public static void main(String[] args) throws Exception { System.out.println("creating the web service client..."); TestClient client = new TestClient("http://localhost:8080/tc_test_project-tc_test_project/TestBean?wsdl"); Test service = client.getTestPort(); System.out.println("calling service.retrieveAll() using the service client"); List<TestEntity> list = service.retrieveAll(); System.out.println("the number of elements in list retrieved using the client is " + list.size()); } I get the following exception: javax.xml.ws.WebServiceException: java.lang.UnsupportedOperationException: setProperty must be overridden by all subclasses of SOAPMessage at org.jboss.ws.core.jaxws.client.ClientImpl.handleRemoteException(ClientImpl.java:396) at org.jboss.ws.core.jaxws.client.ClientImpl.invoke(ClientImpl.java:302) at org.jboss.ws.core.jaxws.client.ClientProxy.invoke(ClientProxy.java:170) at org.jboss.ws.core.jaxws.client.ClientProxy.invoke(ClientProxy.java:150) Now, here's the really interesting part. If I change the JDK that my the code above is running under from JDK6 to JDK5, the exception above goes away! It's really strange. The only way I found for the code above to run under JDK6 was to take the JBOSS_HOME/lib/endorsed folder and copy it to JDK6_HOME/lib. This seems like it shouldn't be necessary, but it is. Is there any other way to make this work other than using the workaround I just described?

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• In C#, are event handler arguments covariant?

  - by Roger Lipscombe

  Maybe covariant's not the word, but if I have a class that raises an event, with (e.g.) FrobbingEventArgs, am I allowed to handle it with a method that takes EventArgs? Here's some code: class Program { static void Main(string[] args) { Frobber frobber = new Frobber(); frobber.Frobbing += FrobberOnFrobbing; frobber.Frob(); } private static void FrobberOnFrobbing(object sender, EventArgs e) { // Do something interesting. Note that the parameter is 'EventArgs'. } } internal class Frobber { public event EventHandler<FrobbingEventArgs> Frobbing; public event EventHandler<FrobbedEventArgs> Frobbed; public void Frob() { OnFrobbing(); // Frob. OnFrobbed(); } private void OnFrobbing() { var handler = Frobbing; if (handler != null) handler(this, new FrobbingEventArgs()); } private void OnFrobbed() { var handler = Frobbed; if (handler != null) handler(this, new FrobbedEventArgs()); } } internal class FrobbedEventArgs : EventArgs { } internal class FrobbingEventArgs : EventArgs { } The reason I ask is that ReSharper seems to have a problem with (what looks like) the equivalent in XAML, and I'm wondering if it's a bug in ReSharper, or a mistake in my understanding of C#.

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• C# naming convention for enum and matching property

  - by Serge - appTranslator

  Hi All, I often find myself implementing a class maintaining some kind of own status property as an enum: I have a Status enum and ONE Status property of Status type. How should I solve this name conflict? public class Car { public enum Status { Off, Starting, Moving }; Status status = Status.Off; public Status Status // <===== Won't compile ===== { get { return status; } set { status = value; DoSomething(); } } } If the Status enum were common to different types, I'd put it outside the class and the problem would be solved. But Status applies to Car only hence it doesn't make sense to declare the enum outside the class. What naming convention do you use in this case? NB: This question was partially debated in comments of an answer of this question. Since it wasn't the main question, it didn't get much visibility. EDIT: Filip Ekberg suggests an IMO excellent workaround for the specific case of 'Status'. Yet I'd be interesting to read about solutions where the name of the enum/property is different, as in Michael Prewecki's answer. EDIT2 (May 2010): My favorite solution is to pluralize the enum type name, as suggested by Chris S. According to MS guidelines, this should be used for flag enums only. But I've come to like it more and more. I now use it for regular enums as well.

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• Is there a library that can decompile a method into an Expression tree, with support for CLR 4.0?

  - by Daniel Earwicker

  Previous questions have asked if it is possible to turn compiled delegates into expression trees, for example: http://stackoverflow.com/questions/767733/converting-a-net-funct-to-a-net-expressionfunct The sane answers at the time were: It's possible, but very hard and there's no standard library solution. Use Reflector! But fortunately there are some greatly-insane/insanely-great people out there who like reverse engineering things, and they make difficult things easy for the rest of us. Clearly it is possible to decompile IL to C#, as Reflector does it, and so you could in principle instead target CLR 4.0 expression trees with support for all statement types. This is interesting because it wouldn't matter if the compiler's built-in special support for Expression<> lambdas is never extended to support building statement expression trees in the compiler. A library solution could fill the gap. We would then have a high-level starting point for writing aspect-like manipulations of code without having to mess with raw IL. As noted in the answers to the above linked question, there are some promising signs but I haven't succeeded in finding if there's been much progress since by searching. So has anyone finished this job, or got very far with it? Note: CLR 4.0 is now released. Time for another look-see.

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• What Scheme Does Ghuloum Use?

  - by Don Wakefield

  I'm trying to work my way through Compilers: Backend to Frontend (and Back to Front Again) by Abdulaziz Ghuloum. It seems abbreviated from what one would expect in a full course/seminar, so I'm trying to fill in the pieces myself. For instance, I have tried to use his testing framework in the R5RS flavor of DrScheme, but it doesn't seem to like the macro stuff: src/ghuloum/tests/tests-driver.scm:6:4: read: illegal use of open square bracket I've read his intro paper on the course, An Incremental Approach to Compiler Construction, which gives a great overview of the techniques used, and mentions a couple of Schemes with features one might want to implement for 'extra credit', but he doesn't mention the Scheme he uses in the course. Update I'm still digging into the original question (investigating options such as Petit Scheme suggested by Eli below), but found an interesting link relating to Gholoum's work, so I am including it here. [Ikarus Scheme](http://en.wikipedia.org/wiki/Ikarus_(Scheme_implementation)) is the actual implementation of Ghuloum's ideas, and appears to have been part of his Ph.D. work. It's supposed to be one of the first implementations of R6RS. I'm trying to install Ikarus now, but the configure script doesn't want to recognize my system's install of libgmp.so, so my problems are still unresolved. Example The following example seems to work in PLT 2.4.2 running in DrEd using the Pretty Big (require lang/plt-pretty-big) (load "/Users/donaldwakefield/ghuloum/tests/tests-driver.scm") (load "/Users/donaldwakefield/ghuloum/tests/tests-1.1-req.scm") (define (emit-program x) (unless (integer? x) (error "---")) (emit " .text") (emit " .globl scheme_entry") (emit " .type scheme_entry, @function") (emit "scheme_entry:") (emit " movl $~s, %eax" x) (emit " ret") ) Attempting to replace the require directive with #lang scheme results in the error message foo.scm:7:3: expand: unbound identifier in module in: emit which appears to be due to a failure to load tests-driver.scm. Attempting to use #lang r6rs disables the REPL, which I'd really like to use, so I'm going to try to continue with Pretty Big. My thanks to Eli Barzilay for his patient help.

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• Objects in JavaScript defined and undefined at the same time (in a FireFox extension)

  - by Alexey Romanov

  I am chasing down a bug in a FireFox extension. I've finally managed to see it for myself (I've only had reports before) and I can't understand how what I saw is possible. One error message from my extension in the Error Console is "gBrowser is not defined". This by itself would be surprising enough, since the overlay is over browser.xul and navigator.xul, and I expect gBrowser to be available from both. Even worse is the actual place where it happens: line 101 of nextplease.js. That is, inside the function isTopLevelDocument, which is only called from onContentLoaded, which is only called from onLoad here: gBrowser.addEventListener(this.loadType, function (event) { nextplease.loadListener.onContentLoaded(event); }, true); So gBrowser is defined in onLoad, but somehow undefined in isTopLevelDocument. When I tried to actually use the extension, I got another error: "nextplease is not defined". The interesting thing is that it happened on lines 853 and 857. That is, inside the functions nextplease.getNextLink = function () { nextplease.getLink(window.content, nextplease.NextPhrasesMap, nextplease.NextImagesMap, nextplease.isNextRegExp, nextplease.NEXT_SEARCH_TYPE); } nextplease.getPrevLink = function () { nextplease.getLink(window.content, nextplease.PrevPhrasesMap, nextplease.PrevImagesMap, nextplease.isPrevRegExp, nextplease.PREV_SEARCH_TYPE); } So nextplease is somehow defined enough to call these functions, but isn't defined inside them. Finally, executing typeof(nextplease) in Execute JS returns "object". Same for gBrowser. How can this happen? Any ideas?

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• Why does the Chrome spacing work in one JS file and not the other?

  - by Matrym

  If you highlight and copy the text in the first paragraph on this page, then paste it into a rich text editor (dreamweaver or gmail in rich text mode), you will see that some of the text is automagically linked. Basically, it works: http://seox.org/link-building-pro.html -- http://seox.org/lbp/old-pretty.js I'm trying to build a second version, but somewhere along the way I broke it. If you go along with the same process on this new url, spacing before and after the link are removed in Chrome: http://seox.org/test.html -- http://seox.org/lbp/lb-core.js Why does the spacing work correctly in the first one, but not in the second? More importantly, how do I fix the second one so that it doesn't bug out? I asked a variation of this question before, and got a helpful and interesting answer, but hopefully I've asked the question with full detail this time around. Thanks in advance for your time! Edit: I've added a bounty to this post, and would greatly appreciate precise instructions on how to fix the bug (rather than general suggestions. To better illustrate the bug, I've copied the gray box (from the second page) below. Note how the spacing is removed before and after the a tags: Link Building 2 is an amazing tool that helps your website visitors share your content, with proper attribution. It connects to email, social sharing sites, eCommerce sites, and is the<a href="http://seox.org/test.html#seo">SEO</a>'s best friend. Think of it as the sneeze in the viral marketing metaphor. <div> <p id="credit"><br /> Read more about<a href="http://seox.org/test.html">Text Citations</a>by<a href="http://seox.org">seox.org</a></p> </div>

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• Code golf: combining multiple sorted lists into a single sorted list

  - by Alabaster Codify

  Implement an algorithm to merge an arbitrary number of sorted lists into one sorted list. The aim is to create the smallest working programme, in whatever language you like. For example: input: ((1, 4, 7), (2, 5, 8), (3, 6, 9)) output: (1, 2, 3, 4, 5, 6, 7, 8, 9) input: ((1, 10), (), (2, 5, 6, 7)) output: (1, 2, 5, 6, 7, 10) Note: solutions which concatenate the input lists then use a language-provided sort function are not in-keeping with the spirit of golf, and will not be accepted: sorted(sum(lists,[])) # cheating: out of bounds! Apart from anything else, your algorithm should be (but doesn't have to be) a lot faster! Clearly state the language, any foibles and the character count. Only include meaningful characters in the count, but feel free to add whitespace to the code for artistic / readability purposes. To keep things tidy, suggest improvement in comments or by editing answers where appropriate, rather than creating a new answer for each "revision". EDIT: if I was submitting this question again, I would expand on the "no language provided sort" rule to be "don't concatenate all the lists then sort the result". Existing entries which do concatenate-then-sort are actually very interesting and compact, so I won't retro-actively introduce a rule they break, but feel free to work to the more restrictive spec in new submissions. Inspired by http://stackoverflow.com/questions/464342/combining-two-sorted-lists-in-python

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• Are Parameters really enough to prevent Sql injections?

  - by Rune Grimstad

  I've been preaching both to my colleagues and here on SO about the goodness of using parameters in SQL queries, especially in .NET applications. I've even gone so far as to promise them as giving immunity against SQL injection attacks. But I'm starting to wonder if this really is true. Are there any known SQL injection attacks that will be successfull against a parameterized query? Can you for example send a string that causes a buffer overflow on the server? There are of course other considerations to make to ensure that a web application is safe (like sanitizing user input and all that stuff) but now I am thinking of SQL injections. I'm especially interested in attacks against MsSQL 2005 and 2008 since they are my primary databases, but all databases are interesting. Edit: To clarify what I mean by parameters and parameterized queries. By using parameters I mean using "variables" instead of building the sql query in a string. So instead of doing this: SELECT * FROM Table WHERE Name = 'a name' We do this: SELECT * FROM Table WHERE Name = @Name and then set the value of the @Name parameter on the query / command object.

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• NSDate out of scope

  - by therealtkd

  Having problems with out of scope for NSDate in an iphone app. I have an interface defined like this: @interface MyObject : NSoObject { NSMutableArray *array; BOOL checkThis; NSDate *nextDue; } Now in the implementation I have this: -(id) init { if( (self=[super init]) ) { checkThis = NO; array = [[NSMutableArray alloc] init]; nextDue = [[NSDate date] retain]; NSDate *testDate = [NSDate date]; } return self; } Now, if I trace through the init, before I actually assign the variables checkThis shows as boolean. array shows as pointer 0x0 because it hasn't ben assigned. But the nextDue is showing as 'out of scope'. I don't understand why this is out of scope but the other variables aren't. If I trace through the code until after the variables are assigned, array now shows as being correctly assigned but nextDue is still out of scope. Interestingly, the testDate variable is assigned just fine and the debugger shows this as a valid date. Further interesting point is if I move the mouse over the testDate variable while I am debugging, it shows as an 'NSDate *' type which I would expect since that's its definition. Yet the nextDue, which to me is defined the same way is showing as a '_NSCFDate *'. Any googling I did on the subject said that the retain is the problem, but its actually out of scope before I even try to assign the variable. However, in another class, the same definition for NSDate work ok. It shows as nil before a value is assigned to it. Arghhh

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