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  • WPF custom user widgets. Will UI components be standardized?

    - by Andrew Florko
    There are lots of articles and video lessons that describe how to create your unique user widget (graphical control) with WPF. There are tons of technical details what is behind the scene and I feel people enthusiasm with ability to customize widgets as never before. I remember those days when VCL library (Delphi) appeared and there was the same enthusiasm in VCL widgets area. Ability to create VCL controls was nearly the must when you was applying for a job as Delphi developer. This situation continued for several years till professional sophisticated 3'd party UI libraries appeared. Hardly you'll have to create your own VCL widget nowadays. Will WPF widgets enthusiasm die as VCL one?

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  • System.Linq.Dynamic and DateTime

    - by Matthew Hood
    I am using System.Linq.Dynamic to do custom where clauses from an ajax call in .Net MVC 1.0. It works fine for strings, int etc but not for DateTime, I get the exception cannot compare String to DateTime. The very simple test code is items = items.Where(string.Format(@" {0} {1}{2}{1} ", searchField, delimiter, searchString)); Where searchField will be for example start_date and the data type is DateTime, delimiter is " (tried with nothing as well) and searchString will be 01-Jan-2009 (tried with 01/01/2009 as well) and items is an IQueryable from LinqToSql. Is there a way of specifying the data type in a dynamic where, or is there a better approach. It is currently already using some reflection to work out what type of delimiter is required.

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  • Scalable (half-million files) version control system

    - by hashable
    We use SVN for our source-code revision control and are experimenting using it for non-source-code files. We are working with a large set (300-500k) of short (1-4kB) text files that will be updated on a regular basis and need to version control it. We tried using SVN in flat-file mode and it is struggling to handle the first commit (500k files checked in) taking about 36 hours. On a daily basis, we need the system to be able to handle 10k modified files per commit transaction in a short time (<5 min). My questions: Is SVN the right solution for my purpose. The initial speed seems too slow for practical use. If Yes, is there a particular svn server implementation that is fast? (We are currently using the gnu/linux default svn server and command line client.) If No, what are the best f/oss/commercial alternatives Thanks

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  • What is an efficient way to find a non-colliding rectangle nearest to a location

    - by hyn
    For a 2D game I am working on, I am using y axis sorting in a simple rectangle-based collision detection. This is working fine, and now I want to find the nearest empty rectangle at a given location with a given size, efficiently. How can I do this? Is there an algorithm? I could think of a simple brute force grid test (with each grid the size of the empty space we're looking for) but obviously this is slow and not even a complete test.

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  • When does it make sense to use a map?

    - by kiwicptn
    I am trying to round up cases when it makes sense to use a map (set of key-value entries). So far I have two categories (see below). Assuming more exist, what are they? Please limit each answer to one unique category and put up an example. Property values (like a bean) age -> 30 sex -> male loc -> calgary Presence, with O(1) performance peter -> 1 john -> 1 paul -> 1

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  • How does the Amazon Recommendation feature work?

    - by Rachel
    What technology goes in behind the screens of Amazon recommendation technology? I believe that Amazon recommendation is currently the best in the market, but how do they provide us with such relevant recommendations? Recently, we have been involved with similar recommendation kind of project, but would surely like to know about the in and outs of the Amazon recommendation technology from a technical standpoint. Any inputs would be highly appreciated. Update: This patent explains how personalized recommendations are done but it is not very technical, and so it would be really nice if some insights could be provided. From the comments of Dave, Affinity Analysis forms the basis for such kind of Recommendation Engines. Also here are some good reads on the Topic Demystifying Market Basket Analysis Market Basket Analysis Affinity Analysis Suggested Reading: Data Mining: Concepts and Technique

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  • How strict should I be in the "do the simplest thing that could possible work" while doing TDD

    - by Support - multilanguage SO
    For TDD you have to Create a test that fail Do the simplest thing that could possible work to pass the test Add more variants of the test and repeat Refactor when a pattern emerge With this approach you're supposing to cover all the cases ( that comes to my mind at least) but I'm wonder if am I being too strict here and if it is possible to "think ahead" some scenarios instead of simple discover them. For instance, I'm processing a file and if it doesn't conform to a certain format I am to throw an InvalidFormatException So my first test was: @Test void testFormat(){ // empty doesn't do anything... processor.validate("empty.txt"); try { processor.validate("invalid.txt"); assert false: "Should have thrown InvalidFormatException"; } catch( InvalidFormatException ife ) { assert "Invalid format".equals( ife.getMessage() ); } } I run it and it fails because it doesn't throw an exception. So the next thing that comes to my mind is: "Do the simplest thing that could possible work", so I : public void validate( String fileName ) throws InvalidFormatException { if(fileName.equals("invalid.txt") { throw new InvalidFormatException("Invalid format"); } } Doh!! ( although the real code is a bit more complicated, I found my self doing something like this several times ) I know that I have to eventually add another file name and other test that would make this approach impractical and that would force me to refactor to something that makes sense ( which if I understood correctly is the point of TDD, to discover the patterns the usage unveils ) but: Q: am I taking too literal the "Do the simplest thing..." stuff?

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  • Why does C++ mandate that complex only be instantiated for float, double, or long double?

    - by templatetypedef
    According to the C++ ISO spec, §26.2/2: The effect of instantiating the template complex for any type other than float, double or long double is unspecified. Why would the standard authors explicitly add this restriction? This makes it unspecified, for example, what happens if you make complex<int> or a complex<MyCustomFixedPointType> and seems like an artificial restriction. Is there a reason for this limitation? Is there a workaround if you want to instantiate complex with your own custom type? I'm primarily asking this question because of this earlier question, in which the OP was confused as to why abs was giving bizarre outputs for complex<int>. That said, this still doesn't quite make sense given that we also might want to make complex numbers out of fixed-points types, higher-precision real numbers, etc. Thanks!

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  • Problem Naming an Interface

    - by Jens Schauder
    I have an interface named PropertyFilter which used to take a Propertyand decide if accepts it or not. And the world was good. But now the interface changed, so that implementations may choose to add additional Propertys. For example a Customer property might get expanded into Name and Address properties. I think it is obvious this is not a Filter anymore, but how would you call such a thing?

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  • Reusability, testability, code complexity reduction and showing-off-ability programming importance

    - by Andrew Florko
    There are lots of programming and architecture patterns. Patterns allow to make code cleaner, reusable, more testable & at last (but not at least) to feel the follower a real cool developer. How do you rank these considerations for you? What does affect you most when you decide to apply pattern? I wonder how many times code reusability (especially for MVP, MVC patterns) was important? For example DAL library often shared between projects (it's reusable) but how often controllers/views (abstracted via interfaces) are reused?

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  • What is the preferred way to indent cases in a switch?

    - by neutrino
    Hey there, As I was writing another switch in Eclipse, I once again came across a rather weird (to me, at least) default indentation, which is applied to 'switch' statements: switch (i) { case 1: ... case n: ... } I tend to prefer another way: switch (i) { case 1: ... case n: ... } Which way is more readable and eye-pleasing for you? I'm still not hundred percent determined what's best for me, so I'd like to stick to what's best for other people who would read my code. BTW, you're free to close this question if this is too subjective. :)

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  • MVP pattern. Presenter requires new view instance. Best practice

    - by Andrew Florko
    I try to apply MVP pattern for win.forms application. I have 2 forms: main & child. Main has a button and when you click it - child form should appear. There are 2 views interfaces that forms implement IMainView { event OnClick; ... } IChildView { ... } There are two presenters MainPresenter(IMainView) & ChildPresenter(IChildView) MainPresenter listens to OnClick event and then should create IChildView implementation. MainPresenter { ... MainClicked() { // it's required to create IChildView instance here } } How would you implement such creation typically? Shall IMainView has factory method for IChildView or may be it should be separate Views factory. What would you advise? Or maybe there is some misunderstanding of MVP here? Thank you in advance!

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  • Flow Based Programming

    - by Software Monkey
    I have been doing a little reading on Flow Based Programming over the last few days. There is a wiki which provides further detail. And wikipedia has a good overview on it too. My first thought was, "Great another proponent of lego-land pretend programming" - a concept harking back to the late 80's. But, as I read more, I must admit I have become intrigued. Have you used FBP for a real project? What is your opinion of FBP? Does FBP have a future? In some senses, it seems like the holy grail of reuse that our industry has pursued since the advent of procedural languages.

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  • Fast, Vectorizable method of taking floating point number modulus of special primes?

    - by caffiend
    Is there a fast method for taking the modulus of a floating point number? With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31 without needing division. Can any similar tricks be applied for floating point numbers? Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. The primes I'm interested in would be 2^7 and 2^31, although if there are more efficient ones for floating point numbers, those would be welcome.

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  • Integration tests - "no exceptions are thrown" approach. Does it make sense?

    - by Andrew Florko
    Sometimes integration tests are rather complex to write or developers have no enough time to check output - does it make sense to write tests that make sure "no exceptions are thrown" only? Such tests provide some input parameters set(s) and doesn't check the result, but only make sure code not failed with exception? May be such tests are not very useful but appropriate in situations when you have no time?

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  • Data clean up: are there libraries of common permutations that we can use? Or is there a better appr

    - by anyaelena
    We are working on clean-up and analysis of a lot of human-entered customer data. We need to decide programmatically whether 2 addresses (for example) are the same, even though the data was entered with slight variations. Right now we run each address through fairly simplistic string replacement (replacing avenue with ave, for example), concatenate the fields and compare the results. We are doing something similar with names. At the very least, it seems like our list of search-replace values should already exist somewhere. Or perhaps you can suggest a totally different and superior way to detect matches?

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  • Testing When Correctness is Poorly Defined?

    - by dsimcha
    I generally try to use unit tests for any code that has easily defined correct behavior given some reasonably small, well-defined set of inputs. This works quite well for catching bugs, and I do it all the time in my personal library of generic functions. However, a lot of the code I write is data mining code that basically looks for significant patterns in large datasets. Correct behavior in this case is often not well defined and depends on a lot of different inputs in ways that are not easy for a human to predict (i.e. the math can't reasonably be done by hand, which is why I'm using a computer to solve the problem in the first place). These inputs can be very complex, to the point where coming up with a reasonable test case is near impossible. Identifying the edge cases that are worth testing is extremely difficult. Sometimes the algorithm isn't even deterministic. Usually, I do the best I can by using asserts for sanity checks and creating a small toy test case with a known pattern and informally seeing if the answer at least "looks reasonable", without it necessarily being objectively correct. Is there any better way to test these kinds of cases?

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  • validation of special characters

    - by jpallavi
    I want to validate login name with special characters !@#S%^*()+_-?/<:"';. space using regular expression in ruby on rails. These special characters should not be acceptable. What is the code for that? Thanks, Pallavi

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  • How do I generate a random string of up to a certain length?

    - by slavy13
    I would like to generate a random string (or a series of random strings, repetitions allowed) of length between 1 and n characters from some (finite) alphabet. Each string should be equally likely (in other words, the strings should be uniformly distributed). The uniformity requirement means that an algorithm like this doesn't work: alphabet = "abcdefghijklmnopqrstuvwxyz" len = rand(1, n) s = "" for(i = 0; i < len; ++i) s = s + alphabet[rand(0, 25)] (pseudo code, rand(a, b) returns a integer between a and b, inclusively, each integer equally likely) It doesn't work because shorter lengths are as likely as longer ones, meaning it's more likely to generate a shorter string than a longer one, so the result is not uniform.

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  • How few a files does it take to load a program on Linux?

    - by BCS
    The (hypothetical for now) situation is the user of my system is going to be given a chunk of C code and needs my system to compile and run it in a chroot sandbox that is generated on the fly and I want to require the fewest files in the box as possible. I'm only willing to play with compiler and linker settings (e.g. static link everything I can expect to be able to find) and make some moderate restriction on what the code can expect use (e.g. they can't use arbitrary libs). The question is how simple can I get the sandbox. Clearly I need the executable, but what about an ELF loader and a .so for the system calls? Can I dump either of them and is there something else I'll need?

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