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• Am I Writing Assembly Or NASM?

  - by cam

  I'm fed up with this. I've been trying to just get a grip on assembly for awhile, but I feel like I'm coding towards my compiler rather than a language. I've been using this tutorial, and so far it's giving me hell. I'm using NASM, which may be the problem, but I figured it was the most popular one. I'm simply trying to learn the most general form of assembly, so I decided to learn x86. I keep running into stupid errors, like not being able to increment a variable. Here's the latest one: not being able to use div. mov bx, 0; mov cx, 0; jmp start; start: inc cx; mov ax, cx; div 3; <-- invalid combination of opcode and operand cmp ah,0; jz totalvalue; mov ax, cx; div 5; <-- invalid combination of opcode and operand cmp ah, 0; jz totalvalue; cmp cx, 1000; jz end; totalvalue: add bx,cx; jmp start; jmp end; end: mov ah,4ch; mov al,00; int 21h; Should I change compilers? It seems like division should be standard. Do I need to read two tutorials (one on NASM, and one on x86?). Any specific help on this problem?

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• Eclipse CDT: cannot debug or terminate application

  - by Paul Lammertsma

  I have Eclipse set up fairly nicely to run the G++ compiler through Cygwin. Even the character encoding is set up correctly! There still seems to be something wrong with my configuration: I can't debug. The pause button in the debug view is simply disabled, and no threads appear in my application tree. It seems that gdb is simply not communicating with Eclipse. Presently, I have the debug settings as follows: Debugger: "Cygwin gdb Debugger" GDB debugger: gdb GDB command file: .gdbinit Protocol: Default I should mention here that I have no idea what .gdbinit does; in my project it is merely an empty file. What is wrong with my configuration? Debugging When attempting to terminate the application in debug mode, Eclipse displays the following error: Target request failed: failed to interrupt. I can't kill the process, either; I have to kill its parent gdb.exe, which in turn kills my application. Running When running it normally, a bunch of kill.exes are called, doing nothing, while Eclipse displays the following error: Terminate failed. I can kill FaceDetector.exe from the task manager. Process Explorer This is what it looks like in Process Explorer (debugging left, running right):

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• Default template parameters with forward declaration

  - by Seth Johnson

  Is it possible to forward declare a class that uses default arguments without specifying or knowing those arguments? For example, I would like to declare a boost::ptr_list< TYPE > in a Traits class without dragging the entire Boost library into every file that includes the traits. I would like to declare namespace boost { template<class T> class ptr_list< T >; }, but that doesn't work because it doesn't exactly match the true class declaration: template < class T, class CloneAllocator = heap_clone_allocator, class Allocator = std::allocator<void*> > class ptr_list { ... }; Are my options only to live with it or to specify boost::ptr_list< TYPE, boost::heap_clone_allocator, std::allocator<void*> in my traits class? (If I use the latter, I'll also have to forward declare boost::heap_clone_allocator and include <memory>, I suppose.) I've looked through Stroustrup's book, SO, and the rest of the internet and haven't found a solution. Usually people are concerned about not including STL, and the solution is "just include the STL headers." However, Boost is a much more massive and compiler-intensive library, so I'd prefer to leave it out unless I absolutely have to.

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• Why doesen't it work to write this NSMutableArray to a plist?

  - by Emil

  edited. Hey, I am trying to write an NSMutableArray to a plist. The compiler does not show any errors, but it does not write to the plist anyway. I have tried this on a real device too, not just the Simulator. Basically, what this code does, is that when you click the accessoryView of a UITableViewCell, it gets the indexPath pressed, edits an NSMutableArray and tries to write that NSMutableArray to a plist. It then reloads the arrays mentioned (from multiple plists) and reloads the data in a UITableView from the arrays. Code: NSIndexPath *indexPath = [table indexPathForRowAtPoint:[[[event touchesForView:sender] anyObject] locationInView:table]]; [arrayFav removeObjectAtIndex:[arrayFav indexOfObject:[NSNumber numberWithInt:[[arraySub objectAtIndex:indexPath.row] intValue]]]]; NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; NSString *plistPath = [rootPath stringByAppendingPathComponent:@"arrayFav.plist"]; NSLog(@"%@ - %@", rootPath, plistPath); [arrayFav writeToFile:plistPath atomically:YES]; // Reloads data into the arrays [self loadDataFromPlists]; // Reloads data in tableView from arrays [tableFarts reloadData];

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• How close can I get C# to the performance of C++ for small intensive tasks?

  - by SLC

  I was thinking about the speed difference of C++ to C# being mostly about C# compiling to byte-code that is taken in by the JIT compiler (is that correct?) and all the checks C# does. I notice that it is possible to turn a lot of these functions off, both in the compile options, and possibly through using the unsafe keyword as unsafe code is not verifiable by the common language runtime. Therefore if you were to write a simple console application in both languages, that flipped an imaginary coin an infinite number of times and displayed the results to the screen every 10,000 or so iterations, how much speed difference would there be? I chose this because it's a very simple program. I'd like to test this but I don't know C++ or have the tools to compile it. This is my C# version though: static void Main(string[] args) { unsafe { Random rnd = new Random(); int heads = 0, tails = 0; while (true) { if (rnd.NextDouble() > 0.5) heads++; else tails++; if ((heads + tails) % 1000000 == 0) Console.WriteLine("Heads: {0} Tails: {1}", heads, tails); } } } Is the difference enough to warrant deliberately compiling sections of code "unsafe" or into DLLs that do not have some of the compile options like overflow checking enabled? Or does it go the other way, where it would be beneficial to compile sections in C++? I'm sure interop speed comes into play too then. To avoid subjectivity, I reiterate the specific parts of this question as: Does C# have a performance boost from using unsafe code? Do the compile options such as disabling overflow checking boost performance, and do they affect unsafe code? Would the program above be faster in C++ or negligably different? Is it worth compiling long intensive number-crunching tasks in a language such as C++ or using /unsafe for a bonus? Less subjectively, could I complete an intensive operation faster by doing this?

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• How To Get the Name of the Current Procedure/Function in Delphi (As a String)

  - by Andreas Rejbrand

  Is it possible to obtain the name of the current procedure/function as a string, within a procedure/function? I suppose there would be some "macro" that is expanded at compile-time. My scenario is this: I have a lot of procedures that are given a record and they all need to start by checking the validity of the record, and so they pass the record to a "validator procedure". The validator procedure raises an exception if the record is invalid, and I want the message of the exception to include not the name of the validator procedure, but the name of the function/procedure that called the validator procedure (naturally). That is, I have procedure ValidateStruct(const Struct: TMyStruct; const Sender: string); begin if <StructIsInvalid> then raise Exception.Create(Sender + ': Structure is invalid.'); end; and then procedure SomeProc1(const Struct: TMyStruct); begin ValidateStruct(Struct, 'SomeProc1'); ... end; ... procedure SomeProcN(const Struct: TMyStruct); begin ValidateStruct(Struct, 'SomeProcN'); ... end; It would be somewhat less error-prone if I instead could write something like procedure SomeProc1(const Struct: TMyStruct); begin ValidateStruct(Struct, {$PROCNAME}); ... end; ... procedure SomeProcN(const Struct: TMyStruct); begin ValidateStruct(Struct, {$PROCNAME}); ... end; and then each time the compiler encounters a {$PROCNAME}, it simply replaces the "macro" with the name of the current function/procedure as a string literal.

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• With PascalMock how do I mock a method with an untyped out parameter and an open array parameter?

  - by Oliver Giesen

  I'm currently in the process of getting started with unit testing and mocking for good and I stumbled over the following method that I can't seem to fabricate a working mock implementation for: function GetInstance(const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID = CID_DEFAULT): Boolean; (TImplContextID is just an alias for Integer) I thought it would have to look something like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; begin Result := AddCall('GetInstance') .WithParams([@AIID, AContextID]) .ReturnsOutParams([AInstance]) .ReturnValue; end; But the compiler complains about the .ReturnsOutParams([AInstance]) saying "Bad argument type in variable type array constructor.". Also I haven't found a way to specify the open array parameter AArgs at all. Also, is using the @-notation for the TGUID-typed parameter the right way to go? Is it possible to mock this method with the current version of PascalMock at all?

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• Common practice for higher-order-polymorphism in scala

  - by raichoo

  Hi, I'm trying to grasp higher-order-polymophism in scala by implementing a very basic interface that describes a monad but I come across a problem that I don't really understand. I implemented the same with C++ and the code looks like this: #include <iostream> template <typename T> class Value { private: T value; public: Value(const T& t) { this->value = t; } T get() { return this->value; } }; template < template <typename> class Container > class Monad { public: template <typename A> Container<A> pure(const A& a); }; template <template <typename> class Container> template <typename A> Container<A> Monad<Container>::pure(const A& a) { return Container<A>(a); } int main() { Monad<Value> m; std::cout << m.pure(1).get() << std::endl; return 0; } When trying to do the same with scala I fail: class Value[T](val value: T) class Monad[Container[T]] { def pure[A](a: A): Container[A] = Container[A](a) } object Main { def main(args: Array[String]): Unit = { val m = new Monad[Value] m.pure(1) } } The compiler complains about: [raichoo@lain:Scala]:434> scalac highorder.scala highorder.scala:5: error: not found: value Container Container[A](a) ^ one error found What am I doing wrong here? There seems to be a fundamental concept I don't seem to understand about scala typeconstructors. Regards, raichoo

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• SFINAE failing with enum template parameter

  - by zeroes00

  Can someone explain the following behaviour (I'm using Visual Studio 2010). header: #pragma once #include <boost\utility\enable_if.hpp> using boost::enable_if_c; enum WeekDay {MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY}; template<WeekDay DAY> typename enable_if_c< DAY==SUNDAY, bool >::type goToWork() {return false;} template<WeekDay DAY> typename enable_if_c< DAY!=SUNDAY, bool >::type goToWork() {return true;} source: bool b = goToWork<MONDAY>(); compiler this gives error C2770: invalid explicit template argument(s) for 'enable_if_c<DAY!=6,bool>::type goToWork(void)' and error C2770: invalid explicit template argument(s) for 'enable_if_c<DAY==6,bool>::type goToWork(void)' But if I change the function template parameter from the enum type WeekDay to int, it compiles fine: template<int DAY> typename enable_if_c< DAY==SUNDAY, bool >::type goToWork() {return false;} template<int DAY> typename enable_if_c< DAY!=SUNDAY, bool >::type goToWork() {return true;} Also the normal function template specialization works fine, no surprises there: template<WeekDay DAY> bool goToWork() {return true;} template<> bool goToWork<SUNDAY>() {return false;} To make things even weirder, if I change the source file to use any other WeekDay than MONDAY or TUESDAY, i.e. bool b = goToWork<THURSDAY>(); the error changes to this: error C2440: 'specialization' : cannot convert from 'int' to 'const WeekDay' Conversion to enumeration type requires an explicit cast (static_cast, C-style cast or function-style cast)

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• ArrayList in Java, adding code to methods

  - by yaz

  Why am I getting a compile time error for the two method headers at the end of my code in my class ArrayListTest? ArrayListTest: http://pastebin.com/dUHn9vPr Student: http://pastebin.com/3Vz1Aytr I have a compiler error at the two lines: delete(CS242, s3) replace(CS242, s, s4); When I try to run the code it states: Exception in thread "main" java.lang.Error: Unresolved compilation problems: The method replace(ArrayList<Student>, Student, Student)in the type ArrayListTest is not applicable for the arguments (List<Student>, Student, Student) The method delete(ArrayList<Student>, Student) in the type ArrayListTest is not applicable for the arguments (List<Student>, Student) at ArrayListTest.main(ArrayListTest.java:54) I fixed the compile time errors since I use Eclipse and Eclipse gives options of code you can use to fix the compile time error. I chose to "Change method to 'replace(ArrayList, Student, Student)' to 'replace(List, Student, Student)' Although it fixed that compile time error, I don't understand why I was getting a compile time error to begin with and why that effectively fixed the error I don't really know what missing code I need to write to correct these two methods below: public static void replace(List<Student> cS242, Student oldItem, Student newItem) { public static void delete(List<Student> cS242, Student target){

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• How to force the build to be out of date, when a text file is modified?

  - by demoncodemonkey

  The Scenario My project has a post-build phase set up to run a batch file, which reads a text file "version.txt". The batch file uses the information in version.txt to inject the DLL with a version block using this tool. The version.txt is included in my project to make it easy to modify. It looks a bit like this: @set #Description="TankFace Utility Library" @set #FileVersion="0.1.2.0" @set #Comments="" Basically the batch file renames this file to version.bat, calls it, then renames it back to version.txt afterwards. The Problem When I modify version.txt (e.g. to increment the file version), and then press F7, the build is not seen as out-of-date, so the post-build step is not executed, so the DLL's version doesn't get updated. I really want to include the .txt file as an input to the build, but without anything actually trying to use it. If I #include the .txt file from a CPP file in the project, the compiler fails because it obviously doesn't understand what "@set" means. If I add /* ... */ comments around the @set commands, then the batch file has some syntax errors but eventually succeeds. But this is a poor solution I think. So... how would you do it?

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• Invert a string: Recursion vs iteration in javascript

  - by steweb

  Hi all, one month ago I've been interviewed by some google PTO members. One of the questions was: Invert a string recursively in js and explain the running time by big O notation this was my solution: function invert(s){ return (s.length > 1) ? s.charAt(s.length-1)+invert(s.substring(0,s.length-1)) : s; } Pretty simple, I think. And, about the big-o notation, I quickly answered O(n) as the running time depends linearly on the input. - Silence - and then, he asked me, what are the differences in terms of running time if you implement it by iteration? I replied that sometimes the compiler "translate" the recursion into iteration (some programming language course memories) so there are no differences about iteration and recursion in this case. Btw since I had no feedback about this particular question, and the interviewer didn't answer "ok" or "nope", I'd like to know if you maybe agree with me or if you can explain me whether there could be differences about the 2 kind of implementations. Thanks a lot and Regards!

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• Can I use a *.tag from another *.tag file in the same /WEB-INF/tags folder?

  - by Ytsejammer

  Hello, I am trying to refactor my JSP code so that a small conditional test condition gets reused through a *.tag file. There are some big parts of my UI that depend on the value of a two-state property of an object present in the request. Let's say the property is 'gender' and the object is of type Person. Like I said, I would like to simplify & centralize the test on the gender property using a tag. For this purpose, I created two tag files: /WEB-INF/tags/if-male.tag /WEB-INF/tags/if-female.tag Now, I have another tiny spot that gets repeated in all over my application; let's say is the salutation to my site user. With this idea, I created a tag like this: /WEB-INF/tags/salutation.tag As you can imagine, I am trying to use the if-male/if-female test within the salutation.tag file to output 'Mrs.' or 'Mr.' like this: <%@ tag body-content="empty" %> <%@ taglib prefix="g" uri="/WEB-INF/tags" %> <g:if-male> Mr. </g:if-male> <g:if-female> Mrs. </g:if-female> Is the use of the if-male/if-female tags legal within the salutation.tag file? I have tried with such arrangement, but it looks like the JDeveloper 10.1.3.4 compiler gets confused and cannot deal with the salutation.tag tag invoking the other two tags in the same 'library' (folder under /WEB-INF/tags). The reference works perfectly in Jetty 6 and it looks like it works as well if I deploy the application to OC4J directly without relying on JDeveloper to pre-compile all my JSPs. I hope someone can shed some light on this. Thanks, YJ

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• In languages which create a new scope each time in a loop block, a new local copy of the local loop

  - by Jian Lin

  It seems that in language like C, Java, and Ruby (as opposed to Javascript), a new scope is created for each iteration of a loop block, and the local variable defined for the loop is actually made into a local variable every single time and recorded in this new scope? For example, in Ruby: p RUBY_VERSION $foo = [] (1..5).each do |i| $foo[i] = lambda { p i } end (1..5).each do |j| $foo[j].call() end the print out is: [MacBook01:~] $ ruby scope.rb "1.8.6" 1 2 3 4 5 [MacBook01:~] $ So, it looks like when a new scope is created, a new local copy of i is also created and recorded in this new scope, so that when the function is executed at a later time, the "i" is found in those scope chains as 1, 2, 3, 4, 5 respectively. Is this true? (It sounds like a heavy operation). Contrast that with p RUBY_VERSION $foo = [] i = 0 (1..5).each do |i| $foo[i] = lambda { p i } end (1..5).each do |j| $foo[j].call() end This time, the i is defined before entering the loop, so Ruby 1.8.6 will not put this i in the new scope created for the loop block, and therefore when the i is looked up in the scope chain, it always refer to the i that was in the outside scope, and give 5 every time: [MacBook01:~] $ ruby scope2.rb "1.8.6" 5 5 5 5 5 [MacBook01:~] $ I heard that in Ruby 1.9, i will be treated as a local defined for the loop even when there is an i defined earlier? The operation of creating a new scope, creating a new local copy of i each time through the loop seems heavy, as it seems it wouldn't have matter if we are not invoking the functions at a later time. So when the functions don't need to be invoked at a later time, could the interpreter and the compiler to C / Java try to optimize it so that there is not local copy of i each time?

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• question/problem regarding assigning an array of char *

  - by Fantastic Fourier

  Hi I'm working with C and I have a question about assigning pointers. struct foo { int _bar; char * _car[MAXINT]; // this is meant to be an array of char * so that it can hold pointers to names of cars } int foofunc (void * arg) { int bar; char * car[MAXINT]; struct foo thing = (struct foo *) arg; bar = arg->_bar; // this works fine car = arg->_car; // this gives compiler errors of incompatible types in assignment } car and _car have same declaration so why am I getting an error about incompatible types? My guess is that it has something to do with them being pointers (because they are pointers to arrays of char *, right?) but I don't see why that is a problem. when i declared char * car; instead of char * car[MAXINT]; it compiles fine. but I don't see how that would be useful to me later when I need to access certain info using index, it would be very annoying to access that info later. in fact, I'm not even sure if I am going about the right way, maybe there is a better way to store a bunch of strings instead of using array of char *?

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• C++ Returning a Reference

  - by Devil Jin

  Consider the following code where I am returning double& and a string&. The thing works fine in the case of a double but not in the case of a string. Why is this difference in the behavior? In both the cases compiler does not even throws the Warning: returning address of local variable or temporary as I am returning a reference. #include <iostream> #include <string> using namespace std; double &getDouble(){ double h = 46.5; double &hours = h; return hours; } string &getString(){ string str = "Devil Jin"; string &refStr = str; return refStr; } int main(){ double d = getDouble(); cout << "Double = " << d << endl; string str = getString(); cout << "String = " << str.c_str() << endl; return 0; } Output: $ ./a.exe Double = 46.5 String =

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• PHP autoloader: ignoring non-existing include

  - by Bart van Heukelom

  I have a problem with my autoloader: public function loadClass($className) { $file = str_replace(array('_', '\\'), '/', $className) . '.php'; include_once $file; } As you can see, it's quite simple. I just deduce the filename of the class and try to include it. I have a problem though; I get an exception when trying to load a non-existing class (because I have an error handler which throws exceptions). This is inconvenient, because it's also fired when you use class_exists() on a non-existing class. You don't want an exception there, just a "false" returned. I fixed this earlier by putting an @ before the include (supressing all errors). The big drawback with this, though, is that any parser/compiler errors (that are fatal) in this include won't show up (not even in the logs), resulting in a hard to find bug. What would be the best way to solve both problems at once? The easiest way would be to include something like this in the autoloader (pseudocode): foreach (path in the include_path) { if (is_readable(the path + the class name)) readable = true; } if (!readable) return; But I worry about the performance there. Would it hurt a lot? (Solved) Made it like this: public function loadClass($className) { $file = str_replace(array('_', '\\'), '/', $className) . '.php'; $paths = explode(PATH_SEPARATOR, get_include_path()); foreach ($paths as $path) { if (is_readable($path . '/' . $file)) { include_once $file; return; } } }

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• Creating spotlight in OpenGL scene

  - by Victor Oliveira

  Im studying OpenGL and trying to create a spot light at my application. The code that Im using for my #vertex-shader is below: #:vertex-shader #{ #version 150 core in vec3 in_pos; in vec2 in_tc; out vec2 tc; glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 20.0f); GLfloat spot_direction[] = { -1.0, -1.0, 0.0 }; glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, spot_direction); glEnable(GL_LIGHT0); void main() { vec4 pos= vec4(vec3(1.0)*in_pos - vec3(1.0), 1.0); pos.z=0.0; gl_Position = pos; tc = in_tc; } } The thing is, everytime Im trying to run the code an Error that says: Type: other, Source: api, ID: 131169, Severity: low Message: Framebuffer detailed info: The driver allocated storage for renderbuffer 1. len = 157, written = 0 failed to compile vertex shader of deferred: directional info log for shader deferred: directional vertex info log for shader deferred: directional: ERROR: Unbound variable: when Specifications: Renderer: GeForce GTX 580/PCIe/SSE2 Version: 3.3.0 NVIDIA 319.17 GLSL: 3.30 NVIDIA via Cg compiler Status: Using GLEW 1.9.0 1024 x 768 OS: Linux debian I guess to create this spotlight is pretty much simple, but since Im really new to OpenGL I dont have a clue how to do it until now, even reading sources like: http://www.glprogramming.com/red/chapter05.html#name3 Read also in some place that light spots can get really hard to understand, but I cant avoid this step right now since Im following my lecture schedule. Could anybody help me?

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• rewrite not a member of LiftRules

  - by José Leal

  Hi guys, I was following http://www.assembla.com/wiki/show/liftweb/URL_Rewriting tutorial for url rewritting in liftweb.. but I get this error: error: value rewrite is not a member of object net.liftweb.http.LiftRules .. it is really odd.. and the documentation says that it exists. I'm using idea IDE, and I've done everything from scratch, using the lift maven blank archifact. Some more info: [INFO] ------------------------------------------------------------------------ [INFO] Building Joseph3 [INFO] task-segment: [tomcat:run] [INFO] ------------------------------------------------------------------------ [INFO] Preparing tomcat:run [INFO] [resources:resources {execution: default-resources}] [WARNING] Using platform encoding (UTF-8 actually) to copy filtered resources, i.e. build is platform dependent! [INFO] Copying 0 resource [INFO] [yuicompressor:compress {execution: default}] [INFO] nb warnings: 0, nb errors: 0 [INFO] artifact org.mortbay.jetty:jetty: checking for updates from scala-tools.org [INFO] artifact org.mortbay.jetty:jetty: checking for updates from central [INFO] [compiler:compile {execution: default-compile}] [INFO] Nothing to compile - all classes are up to date [INFO] [scala:compile {execution: default}] [INFO] Checking for multiple versions of scala [INFO] /home/dpz/Scala/Doit/Joseph3/src/main/scala:-1: info: compiling [INFO] Compiling 2 source files to /home/dpz/Scala/Doit/Joseph3/target/classes at 1274922123910 [ERROR] /home/dpz/Scala/Doit/Joseph3/src/main/scala/bootstrap/liftweb/Boot.scala:16: error: value rewrite is not a member of object net.liftweb.http.LiftRules [INFO] LiftRules.rewrite.prepend(NamedPF("ProductExampleRewrite") { [INFO] ^ [ERROR] one error found [INFO] ------------------------------------------------------------------------ [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] wrap: org.apache.commons.exec.ExecuteException: Process exited with an error: 1(Exit value: 1) [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: 19 seconds [INFO] Finished at: Thu May 27 03:02:07 CEST 2010 [INFO] Final Memory: 20M/175M [INFO] ------------------------------------------------------------------------ Process finished with exit code 1 enter code here

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• Does this mimic perfectly a function template specialization?

  - by zeroes00

  Since the function template in the following code is a member of a class template, it can't be specialized without specializing the enclosing class. But if the compiler's full optimizations are on (assume Visual Studio 2010), will the if-else-statement in the following code get optimized out? And if it does, wouldn't it mean that for all practical purposes this IS a function template specialization without any performance cost? template<typename T> struct Holder { T data; template<int Number> void saveReciprocalOf(); }; template<typename T> template<int Number> void Holder<T>::saveReciprocalOf() { //Will this if-else-statement get completely optimized out if(Number == 0) data = (T)0; else data = (T)1 / Number; } //----------------------------------- void main() { Holder<float> holder; holder.saveReciprocalOf<2>(); cout << holder.data << endl; }

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• write to fifo/pipe from shell, with timeout

  - by Tim

  I have a pair of shell programs that talk over a named pipe. The reader creates the pipe when it starts, and removes it when it exits. Sometimes, the writer will attempt to write to the pipe between the time that the reader stops reading and the time that it removes the pipe. reader: while condition; do read data <$PIPE; do_stuff; done writer: echo $data >>$PIPE reader: rm $PIPE when this happens, the writer will hang forever trying to open the pipe for writing. Is there a clean way to give it a timeout, so that it won't stay hung until killed manually? I know I can do #!/bin/sh # timed_write <timeout> <file> <args> # like "echo <args> >> <file>" with a timeout TIMEOUT=$1 shift; FILENAME=$1 shift; PID=$$ (X=0; # don't do "sleep $TIMEOUT", the "kill %1" doesn't kill the sleep while [ "$X" -lt "$TIMEOUT" ]; do sleep 1; X=$(expr $X + 1); done; kill $PID) & echo "$@" >>$FILENAME kill %1 but this is kind of icky. Is there a shell builtin or command to do this more cleanly (without breaking out the C compiler)?

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• What is faster- Java or C# (Or good old C)?

  - by Rexsung

  I'm currently deciding on a platform to build a scientific computational product on, and am deciding on either C#, Java, or plain C with Intels compiler on Core2 Quad CPU's. It's mostly integer arithmetic. My benchmarks so far show Java and C are about on par with each other, and dotNET/C# trails by about 5%- however a number of my coworkers are claiming that dotNET with the right optimizations will beat both of these given enough time for the JIT to do its work. I always assume that the JIT would have done it's job within a few minutes of the app starting (Probably a few seconds in my case, as it's mostly tight loops), so I'm not sure whether to believe them Can anyone shed any light on the situation? Would dotNET beat Java? (Or am I best just sticking with C at this point?). The code is highly multithreaded and data sets are several terabytes in size. Haskell/erlang etc are not options in this case as there is a significant quantity of existing legacy C code that will be ported to the new system, and porting C to Java/C# is a lot simpler than to Haskell or Erlang. (Unless of course these provide a significant speedup). Edit: We are considering moving to C# or Java because they may, in theory, be faster. Every percent we can shave off our processing time saves us tens of thousands of dollars per year. At this point we are just trying to evaluate whether C, Java, or c# would be faster.

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• BlackBerry Library problems. (jre6 + NET_RIM_BLACKBERRY)

  - by kimera84

  Hi Everyone, I'm new in blackberry environement programming, I'm developing an application for this device and there are some probs about libraries that I don't understand. I have the main project called: npoBBerry - his library is NET_RIM_BLACKBERRY (from 4.6.1 version...) it includes other two projects: Npo - his library is standard jre6 (Npo inlcudes NpoCore) NpoCore - his library is standard jre6 Compliance was set... In Java Compiler level is set to 1.4 for all. Now the problem is that I'm not able to build my project. 4 errors: Error preverifying class ch.yek.npo.model.Advertising Error preverifying class ch.yek.npo.repository.Repository$1 Error!: Error: preverifier failed: C:\Program Files\eclipse\plugins\net.rim.eide.componentpack4.6.1_4.6.1.27\components\bin\preverify.ex ... Error!: Error: preverifier failed: C:\Program Files\eclipse\plugins\net.rim.eide.componentpack4.6.1_4.6.1.27\components\bin\preverify.ex ... I know that libraries are differents but maybe I'm missing something. NpoCore represents models, interfaces Npo just take data from a repository NpoBBeryy just use this data from Services... Please help and thanks in advance... :)

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• Ambiguous access to base class template member function

  - by Johann Gerell

  In Visual Studio 2008, the compiler cannot resolve the call to SetCustomer in _tmain below and make it unambiguous: template <typename TConsumer> struct Producer { void SetConsumer(TConsumer* consumer) { consumer_ = consumer; } TConsumer* consumer_; }; struct AppleConsumer { }; struct MeatConsumer { }; struct ShillyShallyProducer : public Producer<AppleConsumer>, public Producer<MeatConsumer> { }; int _tmain(int argc, _TCHAR* argv[]) { ShillyShallyProducer producer; AppleConsumer consumer; producer.SetConsumer(&consumer); // <--- Ambiguous call!! return 0; } This is the compilation error: // error C2385: ambiguous access of 'SetConsumer' // could be the 'SetConsumer' in base 'Producer<AppleConsumer>' // or could be the 'SetConsumer' in base 'Producer<MeatConsumer>' I thought the template argument lookup mechanism would be smart enough to deduce the correct base Producer. Why isn't it? I could get around this by changing Producer to template <typename TConsumer> struct Producer { template <typename TConsumer2> void SetConsumer(TConsumer2* consumer) { consumer_ = consumer; } TConsumer* consumer_; }; and call SetConsumer as producer.SetConsumer<AppleConsumer>(&consumer); // Unambiguous call!! but it would be nicer if I didn't have to...

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• Can't install egenix-mx-base on Django production VPS

  - by Shane

  I have been following these instructions for setting up a Django production server with postgres, apache, nginx, and memcache. My problem is that I cannot get egenix-mx-base to install and without this I cannot get psycopg2 to work and therefore no database access :(. I am attempting this on a VPS running a clean install of Ubuntu Hardy (8.04) and have followed all instructions on the site to a T. The error message is as follows: $ easy_install egenix-mx-base Searching for egenix-mx-base Reading http://pypi.python.org/simple/egenix-mx-base/ Reading http://www.egenix.com/products/python/mxBase/ Reading http://www.lemburg.com/python/mxExtensions.html Reading http://www.egenix.com/ Best match: egenix-mx-base 3.1.3 Downloading http://downloads.egenix.com/python/egenix-mx-base-3.1.3.tar.gz Processing egenix-mx-base-3.1.3.tar.gz Running egenix-mx-base-3.1.3/setup.py -q bdist_egg --dist-dir /tmp/easy_install-iF7qzl/egenix-mx-base-3.1.3/egg-dist-tmp-laxvcS Warning: Can't read registry to find the necessary compiler setting Make sure that Python modules _winreg, win32api or win32con are installed. In file included from mx/TextTools/mxTextTools/mxte.c:42: mx/TextTools/mxTextTools/mxte_impl.h: In function ‘mxTextTools_TaggingEngine’: mx/TextTools/mxTextTools/mxte_impl.h:345: warning: pointer targets in initialization differ in signedness mx/TextTools/mxTextTools/mxte_impl.h:364: warning: pointer targets in initialization differ in signedness mx/URL/mxURL/mxURL.c: In function ‘mxURL_SetFromString’: mx/URL/mxURL/mxURL.c:676: warning: pointer targets in initialization differ in signedness mx/UID/mxUID/mxUID.c: In function ‘mxUID_Verify’: mx/UID/mxUID/mxUID.c:333: warning: pointer targets in passing argument 1 of ‘sscanf’ differ in signedness mx/UID/mxUID/mxUID.c: In function ‘mxUID_New’: mx/UID/mxUID/mxUID.c:462: warning: pointer targets in passing argument 1 of ‘mxUID_CRC16’ differ in signedness error: Setup script exited with error: build/bdist.linux-x86_64-py2.5_ucs4/dumb/egenix_mx_base-3.1.3-py2.5.egg-info: Is a directory Thank you to anyone who takes the time to try to help me.

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