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  • Inexpensive generation of hierarchical unique IDs

    - by romaninsh
    My application is building a hierarchical structure like this: root = { 'id': 'root', 'children': [ { 'name': 'root_foo', 'children': [] }, { 'id': 'root_foo2', 'children': [ { 'id': 'root_foo2_bar', 'children': [] } ] } ] } in other words, it's a tree of nodes, where each node might have child elements and unique identifier I call "id". When a new child is added, I need to generate a unique identifier for it, however I have two problems: identifiers are getting too long adding many children takes slower, as I need to find first available id My requirement is: naming of a child X must be determined only from the state in their ancestors When I re-generate tree with same contents, the IDs must be same or in other words, when we have nodes A and B, creating child in A, must not affect the name given to children of B. I know that one way to optimize would be to introduce counter in each node and append it to the names which will solve my performance issue, but will not address the issue with the "long identifiers". Could you suggest me the algorithm for quickly coming up with new IDs?

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  • Do objects maintain identity under all non-cloning conditions in PHP?

    - by Buttle Butkus
    PHP 5.5 I'm doing a bunch of passing around of objects with the assumption that they will all maintain their identities - that any changes made to their states from inside other objects' methods will continue to hold true afterwards. Am I assuming correctly? I will give my basic structure here. class builder { protected $foo_ids = array(); // set in construct protected $foo_collection; protected $bar_ids = array(); // set in construct protected $bar_collection; protected function initFoos() { $this->foo_collection = new FooCollection(); foreach($this->food_ids as $id) { $this->foo_collection->addFoo(new foo($id)); } } protected function initBars() { // same idea as initFoos } protected function wireFoosAndBars(fooCollection $foos, barCollection $bars) { // arguments are passed in using $this->foo_collection and $this->bar_collection foreach($foos as $foo_obj) { // (foo_collection implements IteratorAggregate) $bar_ids = $foo_obj->getAssociatedBarIds(); if(!empty($bar_ids) ) { $bar_collection = new barCollection(); // sub-collection to be a component of each foo foreach($bar_ids as $bar_id) { $bar_collection->addBar(new bar($bar_id)); } $foo_obj->addBarCollection($bar_collection); // now each foo_obj has a collection of bar objects, each of which is also in the main collection. Are they the same objects? } } } } What has me worried is that foreach supposedly works on a copy of its arrays. I want all the $foo and $bar objects to maintain their identities no matter which $collection object they become of a part of. Does that make sense?

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  • license and copyright assignment

    - by corintiumrope
    I'm currently working on a wordpress plugin. My client gives me a specs doc (a powerpoint presentation, if you can call that a specs doc), and I code the requested functionality. Every time I send him code every file containing code starts with these lines: Author: My Name Copyright: The_client's_company.com License: MIT Expat (http://en.wikipedia.org/wiki/Expat_License) My intention being giving my client complete right to relicense and distribute the code under any other license (as the TOS of the freelancing website requires, plus I know he intends to sell it under a proprietary license), but at the same time giving myself the right to expand and redistribute the plugin under MIT license if I wish to (not that I do). The reason is I am paid only 10USD/hour (this is my first gig) so I want to at least keep the right to reuse parts of the code in other projects or expand it if I want to start a similar project myself when I finish the contract (unlikely, but who knows...) or show it to potential employees. The contract we agreed upon doesn't include any licensing specifications but I've informed him on the emails we've interchanged that although all my work is licensed by default as MIT I'm giving my clients the copyright of the code I produce so they can relicense it at will before distribution. Is this the correct way of achieving that?

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  • What web oriented language would work best with binary data?

    - by Qqwy
    I want to create a service where people can upload files. However, since file storage costs money, I want to compress the files so they take less space. I would want to write my own compression algorithm, however, PHP doesn't have good ways to handle binary data (which is needed for many compression algorithms). So I wondered, what would be a better language to create such a website in? I have knowledge of PHP (and Javascript, HTML and CSS) but no experience with other things like Ruby, Perl, Python, and other web development languages.

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  • How is determined an impact of a requirement change on the existing code?

    - by MainMa
    Hi, How companies working on large projects evaluate an impact of a single modification on an existing code? Since my question is probably not very clear, here's an example: Let's take a sample business application which deals with tasks. In the database, each task has a state, 0 being "Pending", ... 5 - "Finished". A new requirement adds a new state, between 2nd and 3rd one. It means that: A constraint on the values 1 - 5 in the database must be changed, Business layer and code contracts must be changed to add a new state, Data access layer must be changed to take in account that, for example the state StateReady is now 6 instead of 5, etc. The application must implement a new state visually, add new controls for it, new localized strings for tool-tips, etc. When an application is written recently by one developer, it's more or less easy to predict every change to do. On the other hand, when an application was written for years by many people, no single person can anticipate every change immediately, without any investigation. So since this situation (such changes in requirements) is very frequent, I imagine there are already some clever techniques and ways to predict the impact. Is there any? Do you know any books which deal about this subject? Note: my question is not related to How do you deal with changing requirements? question. In fact, I'm not interested in evaluating the cost of a change, but rather the way to predict the parts of an application which will be concerned by the change. What will be those changes and how difficult they are really doesn't matter in my question.

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  • What is a good design model for my new class?

    - by user66662
    I am a beginning programmer who, after trying to manage over 2000 lines of procedural php code, now has discovered the value of OOP. I have read a few books to get me up to speed on the beginning theory, but would like some advice on practical application. So,for example, let's say there are two types of content objects - an ad and a calendar event. what my application does is scan different websites (a predefined list), and, when it finds an ad or an event, it extracts the data and saves it to a database. All of my objects will share a $title and $description. However, the Ad object will have a $price and the Event object will have $startDate. Should I have two separate classes, one for each object? Should I have a 'superclass' with the $title and $description with two other Ad and Event classes with their own properties? The latter is at least the direction I am on now. My second question about this design is how to handle the logic that extracts the data for $title, $description, $price, and $date. For each website in my predefined list, there is a specific regex that returns the desired value for each property. Currently, I have an extremely large switch statement in my constructor which determines what website I am own, sets the regex variables accordingly, and continues on. Not only that, but now I have to repeat the logic to determine what site I am on in the constructor of each class. This doesn't feel right. Should I create another class Algorithms and store the logic there for each site? Should the functions of to handle that logic be in this class? or specific to the classes whos properties they set? I want to take into account in my design two things: 1) I will add different content objects in the future that share $title and $description, but will have their own properties, so, I want to be able to easily grow these as needed. 2) I will add more websites constantly (each with their own algorithms for data extraction) so I would like to plan efficienty managing and working with these now. I thought about extending the Ad or Event class with 'websiteX' class and store its functions there. But, this didn't feel right either as now I have to manage 100s of little website specific class files. Note, I didn't know if this was the correct site or stackoverflow was the better choice. If so, let me know and I'll post there.

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  • How to make a queue switches from FIFO mode to priority mode?

    - by enzom83
    I would like to implement a queue capable of operating both in the FIFO mode and in the priority mode. This is a message queue, and the priority is first of all based on the message type: for example, if the messages of A type have higher priority than the messages of the B type, as a consequence all messages of A type are dequeued first, and finally the messages of B type are dequeued. Priority mode: my idea consists of using multiple queues, one for each type of message; in this way, I can manage a priority based on the message type: just take first the messages from the queue at a higher priority and progressively from lower priority queues. FIFO mode: how to handle FIFO mode using multiple queues? In other words, the user does not see multiple queues, but it uses the queue as if it were a single queue, so that the messages leave the queue in the order they arrive when the priority mode is disabled. In order to achieve this second goal I have thought to use a further queue to manage the order of arrival of the types of messages: let me explain better with the following code snippet. int NUMBER_OF_MESSAGE_TYPES = 4; int CAPACITY = 50; Queue[] internalQueues = new Queue[NUMBER_OF_MESSAGE_TYPES]; Queue<int> queueIndexes = new Queue<int>(CAPACITY); void Enqueue(object message) { int index = ... // the destination queue (ie its index) is chosen according to the type of message. internalQueues[index].Enqueue(message); queueIndexes.Enqueue(index); } object Dequeue() { if (fifo_mode_enabled) { // What is the next type that has been enqueued? int index = queueIndexes.Dequeue(); return internalQueues[index].Dequeue(); } if (priority_mode_enabled) { for(int i=0; i < NUMBER_OF_MESSAGE_TYPES; i++) { int currentQueueIndex = i; if (!internalQueues[currentQueueIndex].IsEmpty()) { object result = internalQueues[currentQueueIndex].Dequeue(); // The following statement is fundamental to a subsequent switching // from priority mode to FIFO mode: the messages that have not been // dequeued (since they had lower priority) remain in the order in // which they were queued. queueIndexes.RemoveFirstOccurrence(currentQueueIndex); return result; } } } } What do you think about this idea? Are there better or more simple implementations?

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  • Is it bad practice to pass instances through several layers?

    - by Puckl
    In my program design, I often come to the point where I have to pass object instances through several classes. For example, if I have a controller that loads an audio file, and then passes it to a player, and the player passes it to the playerRunnable, which passes it again somewhere else etc. It looks kind of bad, but I don´t know how to avoid it. Or is it OK to do this? EDIT: Maybe the player example is not the best because I could load the file later, but in other cases that does not work.

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  • How can I make eclipse look like VS.NET 2010?

    - by Juan Manuel
    I am constantly switching between a project written in C# 4.0 and another one written in Java. I find it very difficult to read the code in Java, and I think it's because of its colors (or lack of them really) Is there any way to mimic the colors that VS.NET 2010 has inside eclipse? (even better would be to replace all its hotkeys for their equivalent in VS.NET, like ctrl+k for ctrl+f3, but I believe it would be utopic)

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  • How to market R at your institute?

    - by ran2
    Okay, I admit there are lots of threads R vs. something. The strengths of R are obvious to most people here. Still though advertising R in an environment that has been preferring various kinds of other software for quite some time is not easy. Moreover, even in the limited time I´ve been dealing with R, it improved so dramatically that I would mention things among its strengths that I would not have listed when I started my personal R-evolution. So, what I am trying to do here is to collect the most recent and striking arguments that can be put in nutshell and be presented easily. What I got on my list so far is: the Springer useR series ggplot2 and its documentation open source CRAN Rapache rcpp rsocket What can you add to this list? SO threads are also very welcome as answers. EDIT: so far, though indeed very helpful, most answers are arguments (pros) why one would want to use R. Do you have some specific hints that I could include in some kind of overview presentation? EDIT2: I wanted to add this link about R's future to the list...

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  • Etiquette when asking questions in an IRC channel

    - by Zarkonnen
    Many larger OSS projects maintain IRC channels to discuss their usage or development. When I get stuck on using a project, having tried and failed to find information on the web, one of the ways I try to figure out what to do is to go into the IRC channel and ask. But my questions are invariably completely ignored by the people in the channel. If there was silence when I entered, there will still be silence. If there is an ongoing conversation, it carries on unperturbed. I leave the channel open for a few hours, hoping that maybe someone will eventually engage me, but nothing happens. So I worry that I'm being rude in some way I don't understand, or breaking some unspoken rule and being ignored for it. I try to make my questions polite, to the point, and grammatical, and try to indicate that I've tried the obvious solutions and why they didn't work. I understand that I'm obviously a complete stranger to the people on the channel, but I'm not sure how to fix this. Should I just lurk in the channel, saying nothing, for a week? That seems absurd too. A typical message I send might be "Hello all - I've been trying to get Foo to work, but I keep on getting a BarException. I tried resetting the Quux, but this doesn't seem to do anything. Does anyone have a suggestion on what I could try?"

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  • Are unit tests really used as documentation?

    - by stijn
    I cannot count the number of times I read statements in the vein of 'unit tests are a very important source of documentation of the code under test'. I do not deny they are true. But personally I haven't found myself using them as documentation, ever. For the typical frameworks I use, the method declarations document their behaviour and that's all I need. And I assume the unit tests backup everything stated in that documentation, plus likely some more internal stuff, so on one side it duplicates the ducumentation while on the other it might add some more that is irrelevant. So the question is: when are unit tests used as documentation? When the comments do not cover everything? By developpers extending the source? And what do they expose that can be useful and relevant that the documentation itself cannot expose?

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  • Can coding style cause or influence memory fragmentation?

    - by Robert Dailey
    As the title states, I'd like to know if coding style can cause or influence memory fragmentation in a native application, specifically one written using C++. If it does, I'd like to know how. An example of what I mean by coding style is using std::string to represent strings (even static strings) and perform operations on them instead of using the C Library (such as strcmp, strlen, and so on) which can work both on dynamic strings and static strings (the latter point is beneficial since it does not require an additional allocation to access string functions, which is not the case with std::string). A "forward-looking" attitude I have with C++ is to not use the CRT, since to do so would, in a way, be a step backwards. However, such a style results in more dynamic allocations, and especially for a long living application like a server, this causes some speculation that memory fragmentation might become a problem.

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  • Non-blocking ORM issues

    - by Nikolay Fominyh
    Once I had question on SO, and found that there are no non-blocking ORMs for my favorite framework. I mean ORM with callback support for asynchronous retrieval. The ORM would be supplied with a callback or some such to "activate" when data has been received. Otherwise ORM needs to be split of in a separate thread to guarantee UI responsiveness. I want to create one, but I have some questions that blocking me from starting development: What issues we can meet when developing ORM? Does word "non-blocking" before word "ORM" will dramatically increase complexity of ORM? Why there are not much non-blocking ORMs around? Update: It looks, that I have to improve my question. We have solutions that already allows us to receive data in non-blocking way. And I believe that not all companies that use such solutions - using raw SQL. We want to create more generic solution, that we can reuse in future projects. What difficulties we can meet?

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  • Languages with a clear distinction between subroutines that are purely functional, mutating, state-changing, etc?

    - by CPX
    Lately I've become more and more frustrated that in most modern programming languages I've worked with (C/C++, C#, F#, Ruby, Python, JS and more) there is very little, if any, language support for determining what a subroutine will actually do. Consider the following simple pseudo-code: var x = DoSomethingWith(y); How do I determine what the call to DoSomethingWith(y) will actually do? Will it mutate y, or will it return a copy of y? Does it depend on global or local state, or is it only dependent on y? Will it change the global or local state? How does closure affect the outcome of the call? In all languages I've encountered, almost none of these questions can be answered by merely looking at the signature of the subroutine, and there is almost never any compile-time or run-time support either. Usually, the only way is to put your trust in the author of the API, and hope that the documentation and/or naming conventions reveal what the subroutine will actually do. My question is this: Does there exist any languages today that make symbolic distinctions between these types of scenarios, and places compile-time constraints on what code you can actually write? (There is of course some support for this in most modern languages, such as different levels of scope and closure, the separation between static and instance code, lambda functions, et cetera. But too often these seem to come into conflict with each other. For instance, a lambda function will usually either be purely functional, and simply return a value based on input parameters, or mutate the input parameters in some way. But it is usually possible to access static variables from a lambda function, which in turn can give you access to instance variables, and then it all breaks apart.)

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  • Just getting started in Spring and my preference is XML config over annotations. Correct or not?

    - by John Munsch
    After having read through some of the Spring docs my inclination is towards using a XML config file rather than annotations on the classes themselves. My reasoning is that by doing so you avoid tying your POJOs to a particular framework. Based on your experience with Spring, are there any advantages that XML configuration have over an annotation based configuration, and if not what are the disadvantages?

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  • How to get lookahead symbol when constructing LR(1) NFA for parser?

    - by greenoldman
    I am reading an explanation (awesome "Parsing Techniques" by D.Grune and C.J.H.Jacobs; p.292 in the 2nd edition) about how to construct an LR(1) parser, and I am at the stage of building the initial NFA. What I don't understand is how to get/compute a lookahead symbol. Here is the example from the book, the grammar: S -> E E -> E - T E -> T T -> ( E ) T -> n n is terminal. The "weird" transitions for me are is the sequence: 1) S -> . E eof 2) E -> . E - T eof 3) E -> . E - T - 4) E -> E . - T - 5) E -> E - . T - (Note: In the above table, the state numbers are in front and the lookahead symbol is at the end.) What puzzles me is that transition from (4) to (5) means reading - token, right? So how is it that - is still a lookahead symbol and even more important why is it that eof is no longer a lookahead symbol? After all in an input such as n - n eof there is only one - symbol. My naive thinking tells me (5) should be written as: 5) E -> E - . T - eof And another thing -- n is terminal. Why it is not used at all as a lookahead symbol? I mean -- we expect to see - or (, it is ok, but lack of n means we are sure it won't appear in input? Update: after more reading I am only more confused ;-) I.e. what is really a lookahead? Because I see such state as (p.292, 2nd column, 2nd row): E -> E . - T eof Lookahead says eof but the incoming input says -. Isn't it a contradiction? And it is not only in this book.

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  • Continuous integration (with iOS and Android projects)

    - by paxx
    I'm trying to make some positive changes in my company and one of the changes is implementing continuous integration. We do mobile development (iOS/Android) so I need a CI that supports both types of projects. As you can tell I don't know a lot about CI but I've googled a little bit and I think that Jenkins and Hudson are the two most popular. I have a two part questions. Your thought on Jenkins and Hudson? Is there a way for CI to check if the project is compiling to the coding standards (like loose coupling and so on)?

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  • Logging in JSON Effect on Performance

    - by Pius
    I see more and more articles about logging in JSON. You can also find one on NodeJS blog. Why does everyone like it so much? I can only see more operations getting involved: A couple new objects being created. Stringifying objects, which either involves calculating string length or multiple string allocations. GCing all the crap that was created. Is there any test on performance when using JSON logging and regular string logging? Do people use JSON (for logging) in enterprise projects?

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  • Is Perforce as good at merging as DVCSs?

    - by dukeofgaming
    I've heard that Perforce is very good at merging, I'm guessing this has to do with that it tracks changes in the form of changelists where you can add differences across several files in a single blow. I think this implies Perforce gathers more metadata and therefore has more information to do smarter merging (at least smarter than Subversion, being Perforce centralized). Since this is similar to how Mercurial and Git handle changes (I know DVCSs track content rather than files), I was wondering if somebody knew what were the subtle differences that makes Perforce better or worse than a DVCS like Mercurial or Git.

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  • I have a library and several small programs that use it: how should I structure my git repositories?

    - by Dan
    I have some code that uses a library that I and others frequently modify (usually only by adding functions and methods). We each keep a local fork of the library for our own use. I also have a lot of small "driver" programs (~100 lines) that use the library and are used exclusively by me. Currently, I have both the driver programs and the library in the same repository, because I frequently make changes to both that are logically connected (adding a function to the library and then calling it). I'd like to merge my fork of the library with my co-workers' forks, but I don't want the driver programs to be part of the merged library. What's the best way to organize the git repositories for a large, shared library that needs to be merged frequently and a number of small programs that have changes that are connected to changes in the library?

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  • Question about a simple design problem

    - by Uri
    At work I stumbled uppon a method. It made a query, and returned a String based on the result of the query, such as de ID of a customer. If the query didn't return a single customer, it'd return a null. Otherwise, it'd return a String with the ID's of them. It looked like this: String error = getOwners(); if (error != null) { throw new Exception("Can't delete, the flat is owned by: " + error); } ... Ignoring the fact that getCustomers() returns a null when it should instead return an empty String, two things are happening here. It checks if the flat is owned by someone, and then returns them. I think a more readable logic would be to do this: if (isOwned) { throw new Exception("Can't delete, the flat is owned by: " + getOwners()); } ... The problem is that the first way does with one query what I do with two queries to the database. What would be a good solution involving good design and efficiency for this?

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  • Shouldn't recruitment be the other way round?

    - by Fanatic23
    I really don't know why nobody's thought of this so far, but recruitment should be the other way round. Engineers should have some sort of a common platform where they register skills or domains they are interested in, demonstrate their capabilities and companies should take it up from there. I think this is way more effective since if you are paid well to do work that you love doing, you will generally make a fine job out of it. Does anybody know of some recruitment platform like this?

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  • Is MUMPS alive?

    - by ern0
    At my first workplace we were using Digital Standard MUMPS on a PDP 11-clone (TPA 440), then we've switched to Micronetics Standard MUMPS running on a Hewlett-Packard machine, HP-UX 9, around early 90's. Is still MUMPS alive? Are there anyone using it? If yes, please write some words about it: are you using it in character mode, does it acts as web server? etc. (I mean Caché, too.) If you've been used it, what was your feelings about it? Did you liked it?

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  • .NET Dependency Management Systems

    - by StriplingWarrior
    I have some .NET projects that are starting to get large enough to merit looking into Dependency Management solutions, so we don't have to copy binaries from one project to another. Here's what I've found so far: NPanday is based on a port of Maven. I can't tell how recently it was worked on, but the last release was in May 2011. NuGet seems to be under active development, and it appears to have support directly from Microsoft. Some people complained that it "only addresses dependency resolution," but I don't know what else it should address, or whether it has added more features since that point. It does appear to have recently added the ability to import binaries as part of the build process so we don't have to commit them to our repositories. Refix appears to still be in Beta, after having received no attention since Sept 2011. Would somebody with recent experience using any of these dependency management tools (or any others that work well) share your experience? Is NuGet mature enough to use it for dependency management? If not, what does it lack?

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