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  • How to pass non-fatal warnings from a library

    - by wRAR
    A library function parses a file and returns an object. If a parser encounters unknown data, missing values etc., it shouldn't throw an exception and stop parsing (because this is not fatal), but there should be a way to pass information about these things to a caller (so that warnings can be displayed in the UI, for example). How can these warning be returned? I'm thinking of passing a callback function/object into the library, are there any other possible solutions?

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  • How to Check Authenticity of an AJAX Request

    - by Alex Reisner
    I am designing a web site in which users solve puzzles as quickly as they can. JavaScript is used to time each puzzle, and the number of milliseconds is sent to the server via AJAX when the puzzle is completed. How can I ensure that the time received by the server was not forged by the user? I don't think a session-based authenticity token (the kind used for forms in Rails) is sufficient because I need to authenticate the source of a value, not just the legitimacy of the request. Is there a way to cryptographically sign the request? I can't think of anything that couldn't be duplicated by a hacker. Is any JavaScript, by its exposed, client-side nature, subject to tampering? Am I going to have to use something that gets compiled, like Flash? (Yikes.) Or is there some way to hide a secret key? Or something else I haven't thought of? Update: To clarify, I don't want to penalize people with slow network connections (and network speed should be considered inconsistent), so the timing needs to be 100% client-side (the timer starts only when we know the user can see the puzzle). Also, there is money involved so no amount of "trusting the user" is acceptable.

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  • Language independent logic question

    - by Sam
    If one has three fields in a db that they are querying an object by.... One of these fields must always be an associations id. Concerning the other two fields "only one needs to be true" What interpretation do you take or make of "only one needs to be true"?

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  • Arguments against Create or Update

    - by Nix
    Recently someone stated that they thought all Creates should be CreateOrUpdates. Instinctively i thought bad, but now I am trying to find out if I have any grounds. Situation interface IService{ void Create(Object a); void Update(Object a); } or interface IService{ void CreateOrUpdate(Object a); } My first thought is if you implemented everything CreateOrUpdate then you have no control if someone accidentally sends you wrong data, or concurrency issues where someone changes a "primary" field right before you call update.... But if you remove those cases, are there any other cons?

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  • How do software events work internally?

    - by Duddle
    Hello! I am a student of Computer Science and have learned many of the basic concepts of what is going on "under the hood" while a computer program is running. But recently I realized that I do not understand how software events work efficiently. In hardware, this is easy: instead of the processor "busy waiting" to see if something happened, the component sends an interrupt request. But how does this work in, for example, a mouse-over event? My guess is as follows: if the mouse sends a signal ("moved"), the operating system calculates its new position p, then checks what program is being drawn on the screen, tells that program position p, then the program itself checks what object is at p, checks if any event handlers are associated with said object and finally fires them. That sounds terribly inefficient to me, since a tiny mouse movement equates to a lot of cpu context switches (which I learned are relatively expensive). And then there are dozens of background applications that may want to do stuff of their own as well. Where is my intuition failing me? I realize that even "slow" 500MHz processors do 500 million operations per second, but still it seems too much work for such a simple event. Thanks in advance!

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  • When may I ask a question to fellow developers? (Rules before asking questions).

    - by Zwei Steinen
    I assigned a quite simple task to one junior developer today, and he kept pinging me EVERY 5 minutes for HOURS, asking STEP BY STEP, what to do. Whenever something went wrong, he simply copy&pasted the log and basically wrote, "An exception occurred. What should I do?" So I finally had to tell him, "If you want to be a developer, please start thinking a little bit. Read the error message. That's what they are for!". I also however, tell junior developers to ask questions before spending too much time trying to solve it themselves. This might sound contradictory, but I feel there is some kind of an implicit rule that distinguishes questions that should be asked fairly quickly and that should not (and I try to follow those rules when I ask questions..) So my question is, do you have any rules that you follow, or expect others to follow on asking questions? If so, what are they? Let me start with my own. If you have struggled for more than 90 min, you may ask that question (exceptions exists). If you haven't struggled for more than 15 min, you may not ask that question (if you are sure that the answer can not be found within 15 min, this rule does not have to apply). If it is completely out of your domain and you do not plan to learn that domain, you may ask that question after 15 min (e.g. if I am a java programmer and need to back up the DB, I may ask the DBA what procedure to follow after googling for 15 min). If it is a "local" question, whose answer is difficult to derive or for which resources is difficult to get (e.g. asking an colleague "what method xxx does" etc.), you may ask that question after 15 min. If the answer for it is difficult to derive, and you know that the other person knows the answer, you may ask the question after 15 min (e.g. asking a hibernate expert "What do I need to change else to make this work?". If the process to derive the answer is interesting and is a good learning opportunity, you may ask for hints but you may not ask for answers! What are your rules?

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  • Is programming overrated?

    - by aengine
    [Subjective and intended to be a community wiki] I am sorry for such an offensive question: But here are my arguments Most of the progress in "computing" has came from non-programming sources. i.e. People invented faster microprocessors and better routers and novel memory devices. I dont think on average people are writting more efficient programs than those written 10 years ago. And the newer and popular languages are infact slower than C. though speed is one of the lesser criterias. Most of the progress came from novel paradigms. Web, Internet, Cloud computing and Social networking are novel paradigms and did not involve progress in programming as such. Heck even facebook was written in PHP and not some extreme language. Though it did face scalability issues (same with twitter) but i believe money and better programmers (who came in much later) took care of that. Thus ideating capability trumped programming capability/ Even things like Map-Reduce, Column oriented database and Probablistic algorithms (E.g. bloom filters) came from hardcore Algorithms research, rather than some programming convention. Thus my final point is why programming skill is so overstressed? To point a recent example about how only 10% of programmers can "write code" (binary search) without debugging. Isnt it a bit hypocritical, considering your real successs lies in coming up with better algorithm or a novel feature rather than getting right first time???

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  • Details to log when starting an application

    - by Karl
    To help support and anyone who may use one of my applications I tend to log a few things during the application startup. Currently I log: Start Time App Name App Author App Version App Classpath Current working directory Java vendor Java version Max heap size Taking into consideration this application may be used / supported by a whole host of people can anyone think of any other vital details which we / others should log for good practice?

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  • Generate unique ID from multiple values with fault tolerance

    - by ojreadmore
    Given some values, I'd like to make a (pretty darn) unique result. $unique1 = generate(array('ab034', '981kja7261', '381jkfa0', 'vzcvqdx2993883i3ifja8', '0plnmjfys')); //now $unique1 == "sqef3452y"; I also need something that's pretty close to return the same result. In this case, 20% of the values is missing. $unique2 = generate(array('ab034', '981kja7261', '381jkfa0', 'vzcvqdx2993883i3ifja8')); //also $unique2 == "sqef3452y"; I'm not sure where to begin with such an algorithm but I have some assumptions. I assume that the more values given, the more accurate the resulting ID – in other words, using 20 values is better than 5. I also assume that a confidence factor can be calculated and adjusted. What would be nice to have is a weight factor where one can say 'value 1 is more important than value 3'. This would require a multidimensional array for input instead of one dimension. I just mashed on the keyboard for these values, but in practice they may be short or long alpha numeric values.

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  • Pi/Infinite Numbers

    - by Ben Shelock
    I'm curious about infinite numbers in computing, in particular pi. For a computer to render a circle it would have to understand pi. But how can it if it is infinite? Am I looking too much into this? Would it just use a rounded value?

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  • Optimality of Binary Search

    - by templatetypedef
    Hello all- This may be a silly question, but does anyone know of a proof that binary search is asymptotically optimal? That is, if we are given a sorted list of elements where the only permitted operation on those objects is a comparison, how do you prove that the search can't be done in o(lg n)? (That's little-o of lg n, by the way.) Note that I'm restricting this to elements where the only operation permitted operation is a comparison, since there are well-known algorithms that can beat O(lg n) on expectation if you're allowed to do more complex operations on the data (see, for example, interpolation search). Thanks so much! This has really been bugging me since it seems like it should be simple but has managed to resist all my best efforts. :-)

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  • 'goto' usage

    - by Landon
    I've long been under the impression that 'goto' should never be used if possible. While perusing libavcodec (which is written in C) the other day, I noticed multiple uses of it. Is it ever advantageous to use 'goto' in a language that supports loops and functions? If so, why?

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  • Count the number of objects in an Image

    - by kunjaan
    I am investigating the possibility of image processing to identify certain objects and also count them in an image. I will be given a picture and I need to identify the number of boxes present in that image. Does anybody have any experience with any Machine Vision/ Image Processing libraries like ImageJ, Fiji, JAI, jMagick ,Java Vision Toolkit? Which do you think is best suited for the job? What do you guys suggest? If the APIs can be used from Java, it would be better. Thank you. Edit: I am dealing with warehouse brown boxes. Yes I am talking about regular photos. The source is usually a mobile phone picture.

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  • C# logic order and compiler behavior

    - by Terrapin
    In C#, (and feel free to answer for other languages), what order does the runtime evaluate a logic statement? Example: DataTable myDt = new DataTable(); if (myDt != null && myDt.Rows.Count > 0) { //do some stuff with myDt } Which statement does the runtime evaluate first - myDt != null or: myDt.Rows.Count > 0 ? Is there a time when the compiler would ever evaluate the statement backwards? Perhaps when an "OR" operator is involved?

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  • Function for creating color wheels

    - by lbrandy
    This is something I've pseudo-solved many times and never quite found a solution that's stuck with me. The problem is to come up with a way to generate N colors that are as distinguishable as possible where N is a parameter.

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  • Is it wise to rely on default features of a programming language?

    - by George Edison
    Should I frequently rely on default values? For example, in PHP, if you have the following: <?php $var .= "Value"; ?> This is perfectly fine - it works. But what if assignment like this to a previously unused variable is later eliminated from the language? (I'm not referring to just general assignment to an unused variable.) There are countless examples of where the default value of something has changed and so much existing code was then useless. On the other hand, without default values, there is a lot of code redundancy. What is the proper way of dealing with this?

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  • How to know if your Unit Test Fixture is “right-sized”?

    - by leeand00
    How do you know if you "Test Fixture" is right-sized. And by "Test Fixture" I mean a class with a bunch of tests in it. One thing that I've always noticed with my test fixtures is that they get to be kind of verbose; seeing as they could also be not verbose enough, how do you get a sense of when your unit tests are the right size? My assumption is that (at least in the context of web development) you should have one test fixture class per page. I know of a good quote for this and it's: "Perfection is achieved, not when there is nothing left to add, but when there is nothing left to remove." - Antoine de Saint-Exupery.

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  • What are the core mathematical concepts a good developer should know?

    - by Jose B.
    Since Graduating from a very small school in 2006 with a badly shaped & outdated program (I'm a foreigner & didn't know any better school at the time) I've come to realize that I missed a lot of basic concepts from a mathematical & software perspective that are mostly the foundations of other higher concepts. I.e. I tried to listen/watch the open courseware from MIT on Introduction to Algorithms but quickly realized I was missing several mathematical concepts to better understand the course. So what are the core mathematical concepts a good software engineer should know? And what are the possible books/sites you will recommend me?

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