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• centos: linking lib that doesn't have a .pc file for pkg-config

  - by Paulie

  I'm trying to compile svg2pdf on centos. I think I've managed to get the required dependencies installed using yum: sudo yum install librsvg2 sudo yum install cairo The Makefile contains: MYCFLAGS=`pkg-config --cflags librsvg-2.0 cairo-pdf` -Wall -Wpointer-arith -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations - Wnested-externs -fno-strict-aliasing MYLDFLAGS=`pkg-config --libs librsvg-2.0 cairo-pdf` After typing 'make', the first couple of lines of output are: cc `pkg-config --cflags librsvg-2.0 cairo-pdf` -Wall -Wpointer-arith -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wnested-externs -fno-strict-aliasing `pkg-config --libs librsvg-2.0 cairo-pdf` svg2pdf.c -o svg2pdf Package librsvg-2.0 was not found in the pkg-config search path. Perhaps you should add the directory containing `librsvg-2.0.pc' to the PKG_CONFIG_PATH environment variable No package 'librsvg-2.0' found There is no librsvg-2.0.pc on this system (but there is when I installed this using macports on my macbookpro). How should I get this package linked? Should I change the Makefile, and if so, to what? Should I generate the .pc files, and if so, how? Or is there another way to resolve this? Or, has anyone been successful at installing svg2pdf on centos, and, if so, how did you manage it? I don't have much experience on linux, so I might be missing something obvious.

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• Using GKPeerPickerController within a selector from a Cocos2D CCMenuItem

  - by Mark Hazlett

  Hey everyone, So i'm trying to use GameKit along with Cocos2D so that when a user clicks on the multiplayer menu item it will display the GKPeerPickerController. I'm however, running into some snags. It doesn't seem to want to compile. However, it doesn't give me an error inside of the code that's in my selector. Anyways here's the code... @implementation GameOverLayer - (id) init { self = [super init]; if (self != nil) { [CCMenuItemFont setFontSize:20]; [CCMenuItemFont setFontName:@"Helvetica"]; CCMenuItem *start = [CCMenuItemFont itemFromString:@"Play Again!" target:self selector:@selector(startGame:)]; CCMenuItem *connect = [CCMenuItemFont itemFromString:@"Multiplayer" target:self selector:@selector(connect:)]; CCMenu *menu = [CCMenu menuWithItems:start,connect, nil]; [menu alignItemsVertically]; [self addChild:menu]; } return self; } -(void)startGame: (id)sender { [[CCDirector sharedDirector] replaceScene: [HelloWorld scene]]; } -(void)connect: (id)sender { GKPeerPickerController *peerPicker; peerPicker = [[GKPeerPickerController alloc] init]; peerPicker.delegate = self; peerPicker.connectionTypesMask = GKPeerPickerConnectionTypeOnline | GKPeerPickerConnectionTypeNearby; [peerPicker show]; } @end The error message i'm getting is... ".obj_class_name_GKPeerPickerController", referenced from: Literal-Pointer@_OBJC@_cls_refs@GKPeerPickerController in GameOverScene.o Symbol(s) not found Collect2: id returned 1 exit status Any ideas?

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• NHibernate with Framework .NET Framework 2

  - by Daniel Dolz

  Hi. I can not make NHibernate 2.1 work in machines without framework 3.X (basically, windows 2000 SP4, although it happens with XP too). NHibernate doc do no mention this. Maybe you can help? I NEED to make NHibernate 2.1 work in Windows 2000 PCs, so you think this can be done? Thanks! PD: DataBase is SQL 2000/2005. Error is: NHibernate.MappingException: Could not compile the mapping document: Datos.NH_VEN_ComprobanteBF.hbm.xml ---> NHibernate.HibernateException: Could not instantiate dialect class NHibernate.Dialect.MsSql2000Dialect ---> System.Reflection.TargetInvocationException: Se produjo una excepción en el destino de la invocación. ---> System.TypeInitializationException: Se produjo una excepción en el inicializador de tipo de 'NHibernate.NHibernateUtil'. ---> System.TypeLoadException: No se puede cargar el tipo 'System.DateTimeOffset' del ensamblado'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. en NHibernate.Type.DateTimeOffsetType.get_ReturnedClass() en NHibernate.NHibernateUtil..cctor() --- Fin del seguimiento de la pila de la excepción interna --- en NHibernate.Dialect.Dialect..ctor() en NHibernate.Dialect.MsSql2000Dialect..ctor() --- Fin del seguimiento de la pila de la excepción interna --- en System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandle& ctor, Boolean& bNeedSecurityCheck) en System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean fillCache) en System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache) en System.Activator.CreateInstance(Type type, Boolean nonPublic) en NHibernate.Bytecode.ActivatorObjectsFactory.CreateInstance(Type type) en NHibernate.Dialect.Dialect.InstantiateDialect(String dialectName) --- Fin del seguimiento de la pila de la excepción interna --- en NHibernate.Dialect.Dialect.InstantiateDialect(String dialectName) en NHibernate.Dialect.Dialect.GetDialect(IDictionary`2 props) en NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) --- Fin del seguimiento de la pila de la excepción interna --- en NHibernate.Cfg.Configuration.LogAndThrow(Exception exception) en NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) en NHibernate.Cfg.Configuration.ProcessMappingsQueue() and continues...

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• IntelliJ IDEA plugin development: Get classes VirtualFile (or paths) for a specific source VirtualFi

  - by Ran Biron

  Hi all. This is a cross-post from http://www.jetbrains.net/devnet/message/5264436#5264436 - I failed to get any answer on that forum for two weeks now, so I'm re-asking it here (please don't flame). This question refers to plugin development for the IntelliJ IDEA IDE, specifically targeting java development: Is there any API to get the list of .class files for given source file? I'm trying to write a plugin that creates a binary patch jar based on a changelist. I've managed to get the changelist and, from it, a list of source files (VirtualFile). Now I'm trying to get the compiled class files for these source files (I don't mind preforming a "make" or relying on the previous compile output). I've played a bit with ProjectFileIndex but could only find the classes root. I'd hate to do a "dumb" path-based search because inner classes (and inner anonymous classes) would make it difficult to get correctly. Is there such an API? Or am I doomed to parse the paths? Thanks, Ran.

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• Does this use of Monitor.Wait/Pulse have a race condition?

  - by jw

  I have a simple producer/consumer scenario, where there is only ever a single item being produced/consumed. Also, the producer waits for the worker thread to finish before continuing. I realize that kind of obviates the whole point of multithreading, but please just assume it really needs to be this way (: This code doesn't compile, but I hope you get the idea: // m_data is initially null // This could be called by any number of producer threads simultaneously void SetData(object foo) { lock(x) // Line A { assert(m_data == null); m_data = foo; Monitor.Pulse(x) // Line B while(m_data != null) Monitor.Wait(x) // Line C } } // This is only ever called by a single worker thread void UseData() { lock(x) // Line D { while(m_data == null) Monitor.Wait(x) // Line E // here, do something with m_data m_data = null; Monitor.Pulse(x) // Line F } } Here is the situation that I am not sure about: Suppose many threads call SetData() with different inputs. Only one of them will get inside the lock, and the rest will be blocked on Line A. Suppose the one that got inside the lock sets m_data and makes its way to Line C. Question: Could the Wait() on Line C allow another thread at Line A to obtain the lock and overwrite m_data before the worker thread even gets to it? Supposing that doesn't happen, and the worker thread processes the original m_data, and eventually makes its way to Line F, what happens when that Pulse() goes off? Will only the thread waiting on Line C be able to get the lock? Or will it be competing with all the other threads waiting on Line A as well? Essentially, I want to know if Pulse()/Wait() communicate with each other specially "under the hood" or if they are on the same level with lock(). The solution to these problems, if they exist, is obvious of course - just surround SetData() with another lock - say, lock(y). I'm just curious if it's even an issue to begin with.

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• How to use references, avoid header bloat, and delay initialization?

  - by Kyle

  I was browsing for an alternative to using so many shared_ptrs, and found an excellent reply in a comment section: Do you really need shared ownership? If you stop and think for a few minutes, I'm sure you can pinpoint one owner of the object, and a number of users of it, that will only ever use it during the owner's lifetime. So simply make it a local/member object of the owners, and pass references to those who need to use it. I would love to do this, but the problem becomes that the definition of the owning object now needs the owned object to be fully defined first. For example, say I have the following in FooManager.h: class Foo; class FooManager { shared_ptr<Foo> foo; shared_ptr<Foo> getFoo() { return foo; } }; Now, taking the advice above, FooManager.h becomes: #include "Foo.h" class FooManager { Foo foo; Foo& getFoo() { return foo; } }; I have two issues with this. First, FooManager.h is no longer lightweight. Every cpp file that includes it now needs to compile Foo.h as well. Second, I no longer get to choose when foo is initialized. It must be initialized simultaneously with FooManager. How do I get around these issues?

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• Why is an Add method required for { } initialization?

  - by Dan Tao

  To use initialization syntax like this: var contacts = new ContactList { { "Dan", "[email protected]" }, { "Eric", "[email protected]" } }; ...my understanding is that my ContactList type would need to define an Add method that takes two string parameters: public void Add(string name, string email); What's a bit confusing to me about this is that the { } initializer syntax seems most useful when creating read-only or fixed-size collections. After all it is meant to mimic the initialization syntax for an array, right? (OK, so arrays are not read-only; but they are fixed size.) And naturally it can only be used when the collection's contents are known (at least the number of elements) at compile-time. So it would almost seem that the main requirement for using this collection initializer syntax (having an Add method and therefore a mutable collection) is at odds with the typical case in which it would be most useful. I'm sure I haven't put as much thought into this matter as the C# design team; it just seems that there could have been different rules for this syntax that would have meshed better with its typical usage scenarios. Am I way off base here? Is the desire to use the { } syntax to initialize fixed-size collections not as common as I think? What other factors might have influenced the formulation of the requirements for this syntax that I'm simply not thinking of?

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• Should I have different models and views for no user data than for some user data?

  - by Sam Holder

  I'm just starting to learn asp.net mvc and I'm not sure what the right thing to do is. I have a user and a user has a collection of (0 or more) reminders. I have a controller for the user which gets the reminders for the currently logged in user from a reminder service. It populates a model which holds some information about the user and the collection of reminders. My question is should I have 2 different views, one for when there are no reminders and one for when there are some reminders? Or should I have 1 view which checks the number of reminders and displays different things? Having one view seems wrong as then I end up with code in my view which says if (Model.Reminders.Count==0){//do something} else {do something else}, and having logic in the view feels wrong. But if I want to have 2 different views then I'd like to have some code like this in my controller: [Authorize] public ActionResult Index() { MembershipUser currentUser = m_membershipService.GetUser(); IList<Reminder> reminders = m_reminderRepository.GetReminders(currentUser); if (reminders.Count == 0) { var model = new EmptyReminderModel { Email = currentUser.Email, UserName = currentUser.UserName }; return View(model); } else { var model = new ReminderModel { Email = currentUser.Email, UserName = currentUser.UserName, Reminders = reminders }; return View(model); } but obviously this doesn't compile as the View can't take both different types. So if I'm going to do this should I return a specific named view from my controller, depending on the emptiness of the reminders, or should my Index() method redirect to other actions like so: [Authorize] public ActionResult Index() { MembershipUser currentUser = m_membershipService.GetUser(); IList<Reminder> reminders = m_reminderRepository.GetReminders(currentUser); if (reminders.Count == 0) { return RedirectToAction("ShowEmptyReminders"); } else { return RedirectToAction("ShowReminders"); } } which seems nicer but then I need to re-query the reminders for the current user in the ShowReminders action. Or should I be doing something else entirely?

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• Open source file upload with no timeout on IIS6 with ASP, ASP.NET 2.0 or PHP5

  - by Christopher Done

  I'm after a cross-platform cross-browser way of uploading files such that there is no timeout. Uploads aren't necessarily huge -- some just take a long time to upload because of the uploader's slow connection -- but the server times out anyway. I hear that there are methods to upload files in chunks so that somehow the server decides not to timeout the upload. After searching around all I can see is proprietary upload helpers and Java and Flash (SWFUpload) widgets that aren't cross-platform, don't upload in chunks, or aren't free. I'd like a way to do it in any of these platforms (ASP, ASP.NET 2.0 or PHP5), though I am not very clued up on all this .NET class/controller/project/module/visual studio/compile/etc stuff, so some kind of runnable complete project that runs on .NET 2.0 would be helpful. PHP and ASP I can assume will be more straight-forward. Unless I am completely missing something, which I suspect/hope I am, reasonable web uploads are bloody hard work in any language or platform. So my question is: how can I perform web browser uploads, cross-platform, so that they don't timeout, using free software? Is it possible at all?

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• Calculate car filled up times

  - by Ivan

  Here is the question: The driving distance between Perth and Adelaide is 1996 miles. On the average, the fuel consumption of a 2.0 litre 4 cylinder car is 8 litres per 100 kilometres. The fuel tank capacity of such a car is 60 litres. Design and implement a JAVA program that prompts for the fuel consumption and fuel tank capacity of the aforementioned car. The program then displays the minimum number of times the car’s fuel tank has to be filled up to drive from Perth to Adelaide. Note that 62 miles is equal to 100 kilometres. What data will you use to test that your algorithm works correctly? Here is what I've done so far: import java.util.Scanner;// public class Ex4{ public static void main( String args[] ){ Scanner input = new Scanner( System.in ); double distance, consumption, capacity, time; distance = Math.sqrt(1996/62*100); consumption = Math.sqrt(8/100); capacity = 60; time = Math.sqrt(distance*consumption/capacity); System.out.println("The car's fuel tank need to be filled up:" + time + "times"); } } I can compile it but the problem is that the result is always 0.0, can anyone help me what's wrong with it ?

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• How can I share variables between a base class and subclass in Perl?

  - by Jonathan

  I have a base class like this: package MyClass; use vars qw/$ME list of vars/; use Exporter; @ISA = qw/Exporter/; @EXPORT_OK = qw/ many variables & functions/; %EXPORT_TAGS = (all => \@EXPORT_OK ); sub my_method { } sub other_methods etc { } --- more code--- I want to subclass MyClass, but only for one method. package MySubclass; use MyClass; use vars qw/@ISA/; @ISA = 'MyClass'; sub my_method { --- new method } And I want to call this MySubclass like I would the original MyClass, and still have access to all of the variables and functions from Exporter. However I am having problems getting the Exporter variables from the original class, MyClass, to export correctly. Do I need to run Exporter again inside the subclass? That seems redundant and unclear. Example file: #!/usr/bin/perl use MySubclass /$ME/; -- rest of code But I get compile errors when I try to import the $ME variable. Any suggestions?

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• Regex problem in Java in code sample

  - by JaneNY

  I have job with regex in my expressions: example !(FA1_A.i & FA1_M.i) I have operators ! ( ) & | operands have names [a-zA-Z_]*.[a-zA-Z_] I wrote in Java to split on tokens, but it doesn't split on operators and operands If should be !, (, FA1_A.i, &, FA1_m.i, ) . Can anybody tell me what is wrong ? String stringOpеrator = "([!|&()])"; String stringOperand = "(([a-zA-Z_]*)\\.([a-zA-Z_]*))"; String reg=stringOpеrator+"|"+stringOperand; Pattern pattern = Pattern.compile(reg); Matcher m = pattern.matcher(expression); // System.out.println("func: " + function + " item: " + item); while (m.find()) { int a=m.start(); int b=m.end(); String test=expression.substring(m.start(), m.end()); String g=test; tokens.add(new Token(expression.substring(m.start() , m.end()))); //m = pattern.matcher(expression); }

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• Need help in resolving a compiler error: error: invalid conversion from ‘int’ to ‘GIOCondition’

  - by michael

  I have a simple cpp file which uses GIO. I have stripped out everything to show my compile error: Here is the error I get: My.cpp:16: error: invalid conversion from ‘int’ to ‘GIOCondition’ make[2]: *** [My.o] Error 1 Here is the complete file: #include <glib.h> static gboolean read_socket (GIOChannel *gio, GIOCondition condition, gpointer data) { return false; } void createGIOChannel() { GIOChannel* gioChannel = g_io_channel_unix_new(0); // the following is the line causing the error: g_io_add_watch(gioChannel, G_IO_IN|G_IO_HUP, read_socket, NULL); } I have seen other example using gio, and I am doing the same thing in term of calling G_IO_IN|G_IO_HUP. And the documentation http://www.gtk.org/api/2.6/glib/glib-IO-Channels.html, said I only need to include , which I did. Can you please tell me how to resolve my error? One thing I can think of is I am doing this in a cpp file. But g_io_add_watch is a c function? Thank you for any help. I have spent hours on this but did not get anywhere.

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• Find max integer size that a floating point type can handle without loss of precision

  - by Checkers

  Double has range more than a 64-bit integer, but its precision is less dues to its representation (since double is 64-bit as well, it can't fit more actual values). So, when representing larger integers, you start to lose precision in the integer part. #include <boost/cstdint.hpp> #include <limits> template<typename T, typename TFloat> void maxint_to_double() { T i = std::numeric_limits<T>::max(); TFloat d = i; std::cout << std::fixed << i << std::endl << d << std::endl; } int main() { maxint_to_double<int, double>(); maxint_to_double<boost::intmax_t, double>(); maxint_to_double<int, float>(); return 0; } This prints: 2147483647 2147483647.000000 9223372036854775807 9223372036854775800.000000 2147483647 2147483648.000000 Note how max int can fit into a double without loss of precision and boost::intmax_t (64-bit in this case) cannot. float can't even hold an int. Now, the question: is there a way in C++ to check if the entire range of a given integer type can fit into a loating point type without loss of precision? Preferably, it would be a compile-time check that can be used in a static assertion, and would not involve enumerating the constants the compiler should know or can compute.

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• How to call a .NET COM method with an array from delphi using PSafeArray?

  - by Sebastian Godelet

  Hello. I have an .NET (4.0) interface which is implemented with a ServicedComponent COM+ class: interface DotNetIface { void MethodRef(var System.Guid guid); void MethodArray(System.Guid[] guids, params object[] parameters); void MethodCStyle([MarshalAs(UnmanagedType.LPArray, ArraySubType=UnmanagedType.Struct, SizeConst=5)]System.Guid[] guids); } Now I used the Delphi 2007 import wizard to import the type library, and as expected I get the following signatures: procedure MethodRef(var guid : TGuid); procedure MethodArray(guids : PSafeArray); procedure MethodCStyle(var guids : ClrGuid /* from mscorlib_TLB */); If i now call the "ref" method like this it works fine: procedure CallByRef(guid : TGuid); var test : TGuid; begin test := ... comRef.MethodRef(guid); end; Now I also need the array method procedure CallArray(); var localGuid : TGuid; arrayVariant : OleVariant; begin arrayVariant := VarArrayCreate([0,4], varVariant /* dont know here */); arrayVariant[0] := localGuid; /* compile error, cannot cast implicitly */ comRef.MethodArray(PSafeArray(TVarData(arrayVariant.VArray)), /* here this object... PSafeArray works actually*/); end; Now lastly i tried with a c array procedure CallCStyle(); var localGuid : TGuid; arrayOfGuid : array [0..4] of ClrGuid; begin arrayOfGuid[0] := ClrGuid(localGuid); comRef.MethodCStyle(PSafeArray(/* now i dont know put it*/, /* here this object... PSafeArray works actually*/); end; I seriously dont know how to make this work. I hope someone has more experience with COM marshalling thx Side node: I found VT_CLSID which i think can be passed for SafeArrayCreate, but I am not sure how to sue that

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• Windows console

  - by b-gen-jack-o-neill

  Hello. Well, I have a simple question, at least I hope its simple. I was interested in win32 console for a while. Our teacher told us, that windows console is just for DOS and real mode emulation purposes. Well, I know it is not true, becouse DOS applications are runned by emulator which only uses console to display output. Another thing I learned is that console is built into Windows since NT. Well. But what I could not find is, how actually are console programs written to use console. I use Visual C++ for programming (well, for learning). So, the only thing I need to do for using console is select console project. I first thought that windows decides wheather it run app in console or tries to run app in window mode. So I created win32 program and tried printf(). Well, I could not compile it. I know that by definition printf() prints text or variables to stdout. I also found that stdout is the console interface for output. But, I could not find what actually stdout is. So, basicly what I want to ask is, where is the difference between console app and win32 app. I thought that windows starts console when it gets command from "console-family" functions. But obvisously it does not, so there must be some code that actually commands windows to create console interface. And the second question is, when the console is created, how does windows recognize which console terminal is used for what app? I mean, what actually is stdout? Is it a area in memory , or some windows routine that is called? Thanks.

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• Is is possible to populate a datatable using a Lambda expression(C#3.0)

  - by deepak.kumar.goyal

  I have a datatable. I am populating some values into that. e.g. DataTable dt =new DataTable(); dt.Columns.Add("Col1",typeof(int)); dt.Columns.Add("Col2",typeof(string)); dt.Columns.Add("Col3",typeof(DateTime)); dt.Columns.Add("Col4",typeof(bool)); for(int i=0;i< 10;i++) dt.Rows.Add(i,"String" + i.toString(),DateTime.Now,(i%2 == 0)?true:false); There is nothing wrong in this program and gives me the expected output. However, recently , I am learning Lambda and has done some basic knowledge. With that I was trying to do the same thing as under Enumerable.Range(0,9).Select(i = > { dt.Rows.Add(i,"String" + i.toString(),DateTime.Now,(i%2 == 0)?true:false); }); But I am unsuccessful. Is my approach correct(Yes I know that I am getting compile time error; since not enough knowledge on the subject so far)? Can we achieve this by the way I am doing is a big doubt(as I donot know.. just giving a shot). If so , can some one please help me in this regard. I am using C#3.0 and dotnet framework 3.5 Thanks

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• Why String.replaceAll() don't work on this String ?

  - by Aloong

  //This source is a line read from a file String src = "23570006,music,**,wu(),1,exam,\"Monday9,10(H2-301)\",1-10,score,"; //This sohuld be from a matcher.group() when Pattern.compile("\".*?\"") String group = "\"Monday9,10(H2-301)\""; src = src.replaceAll("\"", ""); group = group.replaceAll("\"", ""); String replacement = group.replaceAll(",", "#@"); System.out.println(src.contains(group)); src = src.replaceAll(group, replacement); System.out.println(group); System.out.println(replacement); System.out.println(src); I'm trying to replace the "," between \"s so I can ues String.split() latter. But the above just not working , the result is: true Monday9,10(H2-301) Monday9#@10(H2-301) 23570006,music,**,wu(),1,exam,Monday9,10(H2-301),1-10,score, but when I change the src string to String src = "123\"9,10\"123"; String group = "\"9,10\""; It works well true 9,10 9#@10 1239#@10123 What's the matter with the string???

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• combobox dropdown problem when load AS2 swf file in Flex

  - by him_aeng

  I found the problem about combobox dropdown list in AS2 swf file. My scenario is: There are multiple swf file that was compile from ActionScript2.0 and use Flex to load those swf files in swfLoader component. There are two issue that I found and can't solve it: 1. When I load multiple as2.0 swf file in one flex application the first file that was load will work perfectly but the second and so on file have problem. When I click in their combobox component the dropdown list was not show. 2. swf file that was not first load have problem with popup window also. When the popup was show they can't work properly, I can't make any operation on it such as click button, close popup etc. I solve it by add the empty content AS2.0 swf file in flex to be first swf file that was load and it make something weird happen: When I click button on combobox the dropdown list was appear but it appear on position (x:0, y:0) of its container. I also add the code: this._lockroot = true; in every ActionScript2.0 code but it not solve the problem. I don't know the source of problem. Please help me. Thank.

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• "Ambigous type variable" error when defining custom "read" function

  - by Tener

  While trying to compile the following code, which is enhanced version of read build on readMay from Safe package. readI :: (Typeable a, Read a) => String -> a readI str = case readMay str of Just x -> x Nothing -> error ("Prelude.read failed, expected type: " ++ (show (typeOf > (undefined :: a))) ++ "String was: " ++ str) I get an error from GHC: WavefrontSimple.hs:54:81: Ambiguous type variable `a' in the constraint: `Typeable a' arising from a use of `typeOf' at src/WavefrontSimple.hs:54:81-103 Probable fix: add a type signature that fixes these type variable(s)` I don't understand why. What should be fixed to get what I meant? EDIT: Ok, so the solution to use ScopedTypeVariables and forall a in type signature works. But why the following produces very similar error to the one above? The compiler should infer the right type since there is asTypeOf :: a -> a -> a used. readI :: (Typeable a, Read a) => String -> a readI str = let xx = undefined in case readMay str of Just x -> x `asTypeOf` xx Nothing -> error ("Prelude.read failed, expected type: " ++ (show (typeOf xx)) ++ "String was: " ++ str)

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• Suppress Eclipse compiler errors in in a plug-in

  - by Jan Gorzny

  Hi, I'm currently working on a plug-in for Eclipse that translates some custom Java code (which doesn't necessarily run/compile), to runnable Java code. In particular, the plug-in allows code to be written using classes created or imported during the translation. In general, the pre-translation code runs/compiles fine provided the writer uses import statements at the top of their class files. However, it would be convenient for my users if it was not necessary to import these classes. At the moment, the lack of import statements results in (obvious) compiler errors. Would it be possible to empower my plug-in to either a) suppress/ignore these errors, or b) have Eclipse find these classes automatically, without the use of import statements? I should point out that the translated code would these include the required import statements--but this is not a problem for me. I'm also aware that this could lead to lazy programmers and some bad habits. To clarify, consider the following example of pre-translated code: File f = new File("Somefilename.txt"); which clearly requires the possibly imported class File. Without an import statement (import java.io.File;), Eclipse reports that File can not be resolved to a type. This is the error I'd like to hide in files pertaining to projects created for use with my plug-in. (The translated code would include import java.io.File; so that it would be runnable) In closing, I should point out I'm not necessarily looking for code (though I wouldn't be opposed to it), but rather some links to some relevant tutorials (if they exist), or helpful tips/ideas. Also, as this is my first plug-in, it's entirely possible that what I'd like to do is not possible and that I don't realize it--if this is the case, please let me know, preferably with some justification. Thanks!

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• errors when using c++ bison ---- in the file position.hh

  - by Eric

  firstly I'm not good at English so forgive me. I compile my program with the bison generated files in visual studio and get these errors: ...\position.hh(83): error C2589: '(' : illegal token on right side of '::' ...\position.hh(83): error C2059: syntax error : '::' ...\position.hh(83): error C2589: '(' : illegal token on right side of '::' ...\position.hh(83): error C2059: syntax error : '::' and the corresponding code is: inline void columns (int count = 1) { column = std::max (1u, column + count); } I think the problem is with std::max. If I change std::max to equivalent code then there is problem anymore, but is there a better solution instead of changing the generated code? here is the *.yy file I wrote. // // bison.yy // %skeleton "lalr1.cc" %require "2.4.2" %defines %define parser_class_name "cmd_parser" %locations %debug %error-verbose %code requires { class ParserDriver; } %parse-param { ParserDriver& driver } %lex-param { ParserDriver& driver } %union { struct ast *a; double d; struct symbol *s; struct symlist *sl; int fn; } %code { #include "helper_func.h" #include "ParserDriver.h" std::string error_msg = ""; } %token <d> NUMBER %token <s> NAME %token <fn> FUNC %token EOL %token IF THEN ELSE WHILE DO LET %token SYM_TABLE_OVERFLOW %token UNKNOWN_CHARACTER %nonassoc <fn> CMP %right '=' %left '+' '-' %left '*' '/' %nonassoc '|' UMINUS %type <a> exp stmt list explist %type <sl> symlist %{ extern int yylex(yy::cmd_parser::semantic_type *yylval, yy::cmd_parser::location_type* yylloc); %} %start calclist %% ... grammar rules ...

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• Bubble sort algorithm implementations (Haskell vs. C)

  - by kingping

  Hello. I have written 2 implementation of bubble sort algorithm in C and Haskell. Haskell implementation: module Main where main = do contents <- readFile "./data" print "Data loaded. Sorting.." let newcontents = bubblesort contents writeFile "./data_new_ghc" newcontents print "Sorting done" bubblesort list = sort list [] False rev = reverse -- separated. To see rev2 = reverse -- who calls the routine sort (x1:x2:xs) acc _ | x1 > x2 = sort (x1:xs) (x2:acc) True sort (x1:xs) acc flag = sort xs (x1:acc) flag sort [] acc True = sort (rev acc) [] False sort _ acc _ = rev2 acc I've compared these two implementations having run both on file with size of 20 KiB. C implementation took about a second, Haskell — about 1 min 10 sec. I have also profiled the Haskell application: Compile for profiling: C:\Temp ghc -prof -auto-all -O --make Main Profile: C:\Temp Main.exe +RTS -p and got these results. This is a pseudocode of the algorithm: procedure bubbleSort( A : list of sortable items ) defined as: do swapped := false for each i in 0 to length(A) - 2 inclusive do: if A[i] > A[i+1] then swap( A[i], A[i+1] ) swapped := true end if end for while swapped end procedure I wonder if it's possible to make Haskell implementation work faster without changing the algorithm (there's are actually a few tricks to make it work faster, but neither implementations have these optimizations)

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• program that writes the even and odd numbers

  - by user292489

  enter code herei was writting a program that can read a set of numbers file called dog.txt; and also writes to two file separating odd and even. i was able to compile my program however, the output expected is not the same which was supposed to be even numbers in one file called EVEN, odd numbers in file odd. #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { int i; int even,odd; int num; if (argc != 4) { printf("Usage: executable in_file output_file\n"); exit(0); } FILE *dog = fopen(argv[1], "r"); FILE *feven= fopen(argv[2], "w"); FILE *fodd= fopen (argv[3], "w"); while (fscanf(dog, "%d", &num) != EOF) { if (0==i%2){ i++; printf("even= %d\n", num); } else if(i!=0){ i++; printf("odd= %d\n", num); } } fclose(feven); fclose(fodd); fclose(dog); return 0; } output: even= 1 odd= 2 even= 34 odd= 44 even= 66 odd= 78 even= 94 odd= 21 even= 23 odd= 54 even= 44 odd= 65 even= 78 odd= 68 even= 92

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• Can I build this XPath query dynamically in XSLT?

  - by Martin Doms

  I have a document that looks something like <root> <element> <subelement1 /> <subelement2 /> </element> <element> <subelement2 /> <subelement1 /> </element> </root> In my XSLT sheet in the context of /element[2]/[someNode] I want to get a number that represents the distance of /element[1]/[someNode] (ie, the number of preceding siblings of /element1/[someNode]). For example, in the context of /element[2]/subelement1 I'd like to have some way to get the number 2, the distance from /element[1] to /element[1]/subelement2. I only ever need the distance of the given node name from the first instance of . Intuitively I thought I could construct this like <xsl:variable name="nodename" select="name()" /> <xsl:value-of select="/element[1]/$nodename/preceding-sibling::*" /> but unfortunately this sheet doesn't compile. Is what I'm trying to achieve possible in XSLT?

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