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• Archiving Database Tables using Java

  - by HonorGod

  My application demands archiving database tables between sybase and db2 and vice-a-versa and within(db2 to db2 and sybase to sybase) using java. I am trying to understand the best strategies around in terms performance, implementation, ease of use and scalability. Here is my current process - source and destination tables with the acceptable parameters (from java) are defined within xml. the application reads the source and destination configurations and execute them sequentially. destination is sometime optional when source is just deleting data from a specific table or when the source is just calling a stored procedure. dataset between source and destination is extremely large (in millions) From top of my head, it looks like I can define dependencies between multiple source and destination combination and have them execute in parallel in multiple treads. But will this improve any performance(i hope it will)? Are there any open-source frameworks for data archiving using java? Any other thoughts on the implements side will be really helpful. Thanks

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• undefined reference to static member variable

  - by Max

  Hi. I have this class that has a static member. it is also a base class for several other classes in my program. Here's its header file: #ifndef YARL_OBJECT_HPP #define YARL_OBJECT_HPP namespace yarlObject { class YarlObject { // Member Variables private: static int nextID; // keeps track of the next ID number to be used int ID; // the identifier for a specific object // Member Functions public: YarlObject(): ID(++nextID) {} virtual ~YarlObject() {} int getID() const {return ID;} }; } #endif and here's its implementation file. #include "YarlObject.hpp" namespace yarlObject { int YarlObject::nextID = 0; } I'm using g++, and it returns three undefined reference to 'yarlObject::YarlObject::nextID linker errors. If I change the ++nextID phrase in the constructor to just nextID, then I only get one error, and if I change it to 1, then it links correctly. I imagine it's something simple, but what's going on?

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• Programming tutorials for people with zero experience

  - by www.aegisub.net

  A friend of mine is interested in learning how to program computers, but she knows nothing about programming. I suggested that Python might be a good language to start with, but after some googling, I couldn't find any tutorials that covered both programming and Python in an adequate way. I don't want her to go through the tiresome "learn algorithms in pseudocode first" routine. Instead, I'd like a tutorial that will explain the basic ideas while working towards a real goal, e.g. a very simple console game. Does anyone know of any such tutorials? Do you think that I'm mistaken in how I'm handling this? Is Python a bad choice? I know that something like C, C++ or Java won't work - too many details will be very counterproductive. On the other hand, I think that Lisp might be too mathematical and abstract. Python, on the other hand, will let her even do something like coding primitive graphical games in a short period of time.

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• In c++ is there any Events/delegates/interfaces/notifications! anything?

  - by Bach

  Say i have these classes ViewA and ViewB In objective C using the delegate pattern I could do @protocol ViewBDelegate{ - (void) doSomething(); } then in ViewB interface: id<ViewBDelegate> delegate; then in ViewA implementation i set the delegate: viewB.delegate = self; and now I can call in doSomething from viewB onto any that unknown type delegate. [delegate doSomething]; "C++ How to Program" has been the worse read an can't find simple examples that demonstrates basic design patterns. What i'm looking for in C++ is: events ActionScript and java either delegates or notifications in Objective C anything that allows class A, Class B and Class C to know that ClassX didSomething()!!! thanks

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• What is so great about STL?

  - by Zygrob

  Hello StackOverflow. I am a Java developer trying to learn C++. I have many times read over the web (including StackOverflow) that STL is the best collections library that you can get in *any* language. (Sorry, I do not have any citations atm) However after studying some STL, I am really failing to see what makes STL so special. Would you please shed some light on what sets STL apart from the collection libraries of other languages and make it the _best_ collection library? Thanks in advance, Zygr??b.

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• Double Inner Join generates unexpected error

  - by Itamar Marom

  In my database I have three tables: Users: UserID (Auto Numbering), UserName, UserPassword and a few other unimportant fields. PrivateMessages: MessageID (Auto Numbering), SenderID and a few other fields defining the message content. MessageStatus: MessageID, ReceiverID, MessageWasRead (Boolean) What I need is a query to which I input a user's id and I get all the private messages he has received. In addition, I also need to receive each message's sender UserName. For this I wrote the following query: SELECT Users.*, PrivateMessages.*, MessageStatus.* FROM PrivateMessages INNER JOIN Users ON PrivateMessages.SenderID = Users.UserID INNER JOIN MessageStatus ON PrivateMessages.MessageID = MessageStatus.MessageID WHERE MessageStatus.ReceiverID=[@userid]; But for some reason when I try saving it in my Access database, I get the following error (translated to English by me, since my office is in a different language): Syntax error (missing operator) at expression: "PrivateMessages.SenderID = Users.UserID INNER JOIN MessageStatus ON PrivateMessages.MessageID = MessageStatus.MessageI". Any ideas what could cause this? Thanks.

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• byte-sized bit pattern in C and its relevance?

  - by Nikunj Banka

  I a reading Kerninghan and Ritchie's C programming language book and on page 37 it mentions byte sized bit patterns like : '\013' for vertical tab . '\007' for bell character . My doubts : What is byte sized in it and and what's a bit pattern ? What relevance does this hold and where can I apply it ? Is it in any sense related to escape sequences ? I can't seem to find any information what so ever about these byte sized bit patterns on the web . please help . thanks .

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• Rainbow Tables: How to improve upon them??

  - by CVS-2600Hertz-wordpress-com

  I recently obtained the l0pht-CD for windows and tried it out on my PC and It WORKS!! http://2600hertz.wordpress.com/2009/12/22/100-windows-xp-vista-7-password-recovery/ I have also read http://kestas.kuliukas.com/RainbowTables/ I'm designing a "Login-Simulator" that stores pwd-s in a similar manner. The current implementation will be vulnerable to the above attack. Plz could anyone illustrate (in as simple terms as possible), how to strengthen the rainbow tables against such an attack. MY GOAL : Build "Login-Simulator" to be as secure as possible. (Read Hacking Competition ;-) ) Thank You.

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• PHP readdir() not returning files in alphabetical order

  - by Buggabill

  I am reading through a directory with some pictures and such using a pretty simple implementation of readdir() like the following: if ($handle = opendir($path)) { while (false !== ($szFilename = readdir($handle))) { if ($szFilename[0] !== '.') { if (is_file($path.$szFilename)) { // do stuff } } } } The problem that I am having is that the files are not being read in alphabetical order as the docs for readdir() state: Returns the filename of the next file from the directory. The filenames are returned in the order in which they are stored by the filesystem. Another weird thing is that, on the local testing server, the same code works great. This is running on a server using the LAMP stack in both cases. I know that I can build an array and just sort it, but I was wondering if I was missing something in what I was doing. Thanks for any insight!

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• Track someone's GitHub repo in a branch

  - by drhorrible

  I'm pretty new to Git, and like it a lot so far, but am not sure what do do here. I've forked a github project, and am currently in the process of porting it to another language. For reference, I've created a branch of the code as it was when I made the fork. My problem now is that the original project has been updated, and I can't figure out how to pull those changes into my branch from the original master (because 'origin' points to my github project). Follow-up question for my own education, what command will the owner of the original project have to run in order to pull a change in from my branch into his master branch?

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• Has anybody managed to teach themself strong OOP skills through mainly developing with JavaScript?

  - by yaya3

  I am trying to do this, I'm a full time front-end dev and am aware that I am struglling to achieve this. When I am referring to OOP skills I am referring to understanding and being familiar with concepts like inheritance, polymorphism, encapsulation, abstaction. I am aware that it may be more likely to achieve what I'm after by focusing on another language in my spare time. This is the plan, but I'd be really intrigued to hear if anybody has managed to achieve this purely through JavaScript and how you did it. It'd be even better to hear from strong OOP developers from who use different programming languages to know if they have worked with developers who have managed to achieve this.

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• Does isolation frameworks (Moq, RhinoMock, etc) lead to test overspecification?

  - by Marius

  In Osherove's great book "The Art of Unit Testing" one of the test anti-patterns is over-specification which is basically the same as testing the internal state of the object instead of some expected output. To my experience, using Isolation frameworks can cause the same unwanted side effects as testing internal behavior because one tends to only implement the behavior necessary to make your stub interact with the object under test. Now if your implementation changes later on (but the contract remains the same), your test will suddenly break because you are expecting some data from the stub which was not implemented. So what do you think is the best approach to counter this? 1) Implement your stubs/mocks fully, this has the negative side-effect of potentially making your test less readable and also specifying more than necessary to make your test pass. 2) Favor manual, fully implemented fakes. 3) Implement your stubs/fakes so that they make your test just pass, and then deal with the brittleness that this might introduce.

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• Aspect Oriented Programming vs List<IAction> To execute methods based on conditions

  - by David Robbins

  I'm new to AOP so bear with me. Consider the following scenario: A state machine is used in a workflow engine, and after the state of the application is changed, a series of commands are executed. Depending on the state, different types of commands should be executed. As I see it, one implementation is to create List<IAction> and have each individual action determine whether it should execute. Would a Aspect Oriented process work as well? That is, could you create an aspect that notifies a class when a property changes, and execute the appropriate processes from that class? Would this help centralize the state specific rules?

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• From a programmer's perspective, which is your everyday Python uses?

  - by Vimvq1987

  I've finished my thesis and now having a free time. I intend to learn another language, and Python seems to be a good choice. I'll probably have to use .NET for every day works, but I heard that Python helps programmer a lot, in mean of automation. That would be great if I can write "small" Python scripts to do something automatically. From a programmer's perspective, which is your everyday Python's uses? What did it do to have your works done?

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• Bit conversion operations in PHP

  - by Goro

  Hello, I find myself in need of performing bit-level conversion on variables in PHP. In more detail, I have a bit stream that is read as an integer by hardware, and I need to do some operations on the bits to make it into what its actually supposed to be (a float). I have to do this a few times for different formats, and the functionality I need is Being able to select and move individual bits in a variable Being able to cast statically one type of variable to the other (ie. int to float) I know php natively supports bitwise AND, OR, etc, and shift operations, but I was wondering if: there may already be a library in php that does this sort of thing I would be better off with delegating the calculations to some other language Thanks,

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• Enums With Default Throw Clause?

  - by Tom Tresansky

  I noticed the following in the Java Language spec in the section on enumerations here: link switch(this) { case PLUS: return x + y; case MINUS: return x - y; case TIMES: return x * y; case DIVIDE: return x / y; } throw new AssertionError("Unknown op: " + this); However, looking at the switch statement definition section, I didn't notice this particular syntax (the associated throw statement) anywhere. Can I use this sort of "default case is throw an exception" syntactic sugar outside of enum definitions? Does it have any special name? Is this considered a good/bad practice for short-cutting this behavior of "anything not in the list throws an exception"?

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• What could possibly cause this error when declaring an object inside a class?

  - by M4design

  I'm battling with this assignment :) I've got two classes: Ocean and Grid. When I declare an object of the Grid inside the Ocean: unsigned int sharkCount; Grid grid; The compiler/complainer says: error C2146: syntax error : missing ';' before identifier 'grid' Can you possibly predict what produces this error with the limited info I provided? It seems that as if the Ocean doesn't like the Grid class. Could this be because of the poor implementation of the grid class. BTW the Grid has a default constructor. Yet the error happens in compiling time!. EDIT: They're each in separate header file, and I've included the Grid.h in the Ocean.h.

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• Delphi: OnTimer event of my own Timer never happens

  - by Mikhail

  I need a Timer in a 'no form' Delphi unit, so I do this: unit ... interface type TMyTimer = Class(TTimer) public procedure OnMyTimer(Sender: TObject); end; var MyTimer: TMyTimer; implementation procedure TMyTimer.OnMyTimer(Sender: TObject); begin ... end; initialization MyTimer := TMyTimer.Create(nil); with MyTimer do begin Interval := 1000; Enabled := True; OnTimer := OnMyTimer; end; finalization FreeAndNil(MouseTimer); The problem is that the OnMyTimer procedure is never run. I'll truly appreciate any ideas as to why :-)

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• Auto pointer for unsigned char array?

  - by Gianluca

  I'd need a class like std::auto_ptr for an array of unsigned char*, allocated with new[]. But auto_ptr only calls delete and not delete[], so i can't use it. I also need to have a function which creates and returns the array. I came out with my own implementation within a class ArrayDeleter, which i use like in this example: #include <Utils/ArrayDeleter.hxx> typedef Utils::ArrayDeleter<unsigned char> Bytes; void f() { // Create array with new unsigned char* xBytes = new unsigned char[10]; // pass array to constructor of ArrayDeleter and // wrap it into auto_ptr return std::auto_ptr<Bytes>(new Bytes(xBytes)); } ... // usage of return value { auto_ptr<Bytes> xBytes(f()); }// unsigned char* is destroyed with delete[] in destructor of ArrayDeleter Is there a more elegant way to solve this? (Even using another "popular" library)

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• Parantheses around method invokation: why is the compiler complaining about assignment?

  - by polygenelubricants

  I know why the following code doesn't compile: public class Main { public static void main(String args[]) { main((null)); // this is fine! (main(null)); // this is NOT! } } What I'm wondering is why my compiler (javac 1.6.0_17, Windows version) is complaining "The left hand side of an assignment must be a variable". I'd expect something like "Don't put parantheses around a method invokation, dummy!", instead. So why is the compiler making a totally unhelpful complaint about something that is blatantly irrelevant? Is this the result of an ambiguity in the grammar? A bug in the compiler? If it's the former, could you design a language such that a compiler would never be so off-base about a syntax error like this?

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• Is there a better acts_as_commentable for Rails?

  - by levi rosol

  Here's what I'm looking to do. I have a site where I want the user to be able to leave comments on various Models. acts_as_commentable is the obvious starting point for this, but I'm curious if there is a gem / plug-in with a more robust feature-set. For example: Pre-built partial(s) (w/ or w/o Twitter / FB buttons) Partial(s) that utilize jQuery Twitter and / or FB tunnels (push to the users twitter / FB when they comment) Pre-built mechanism for pushing other users comments to users viewing that Model I can see how some of this functionality could be app specific, however, a generic implementation seems like it would be useful. I'm curious if something like this exists or not.

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• Reliably converting C preprocessor macros to python code

  - by manual-manuel

  Hi, I have a bunch of C macros the operation of which I need to simulate in python. I saw some pointers to pygccxml or ctypeslib etc. Are these the ways to go ? Or is there something out there that is better ? The C macros if and when they change, I would like the python implementation to be auto generated rather than having to make manual modifications. Hence the question. <my_c_header.h> /* #defines type 1 */ #ifdef OS #define NUM_FLAGS (uint16_t)(3) #define NUM_BITS (uint16_t)(8) #else #define NUM_FLAGS (uint16_t)(6) #define NUM_BITS (uint16_t)(16) #endif #define MAKE_SUB_FLAGS (uint16_t)((1<<NUMFLAGS) -1) #define MAKE_TOTAL_FLAGS(x) (uint16_t)((x & MAKE_SUB_FLAGS) >> NUM_BITS) /* #defines type 2 */ #ifdef OS #DO_SOMETHING(X) os_specifc_process(x) #else #DO_SOMETHING(x) #endif /* #defines type 3 */ enum { CASE0, CASE1, CASE2 } #define MY_CASE_0 ((uint16_t)CASE0) #define MY_CASE_1 ((uint16_t)CASE1) #define MY_CASE_2 ((uint16_t)CASE2) #define /*End of file <my_c_header.h> */ Thanks M

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• Compilation hangs for a class with field double d = 2.2250738585072012e-308

  - by 01es

  I have come across an interesting situation. A coworker committed some changes, which would not compile on my machine neither from the IDE (Eclipse) nor from a command line (Maven). The problem manifested in the compilation process taking 100% CPU and only killing the process would help to stop it. After some analysis the cause of the problem was located and resolved. It turned out be a line "double d = 2.2250738585072012e-308" (without semicolon at the end) in one of the interfaces. The following snipped duplicates it. public class WeirdCompilationIssue { double d = 2.2250738585072012e-308 } Why would compiler hang? A language edge case?

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• Using special characters as keywords in latex listings package

  - by sha

  Hi, I am using the listings package for latex. I am using the SQL language definition and am adding some new keywords that I need, using morekeywords=. I have trouble defining some special characters as keywords, for example, I need [], <, &, and - to be considered as keywords and use the keyword style. I have tried adding these verbatim or with a preceding backslash. It did not work. Your help would be greatly appreciated. Thanks.

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• Django refresh page if change data by other user

  - by Fran Sobrino

  I have a test django app. In one page the test show the same question to all users. I'd like that when a user answers correctly, send a signal to other active user's browser to refresh to the next question. I have been learning about signals in django I learning work with them but I don't now how send the "refresh signal" to client browser. I think that it can do with a javascript code that check if a certain value (actual question) change and if change reload the page but I don't know this language and the information that I find was confused. Can anybody help me? Many Thanks.

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