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  • How do I write a constant-space length function in Haskell?

    - by Bill
    The canonical implementation of length :: [a] -> Int is: length [] = 0 length (x:xs) = 1 + length xs which is very beautiful but suffers from stack overflow as it uses linear space. The tail-recursive version: length xs = length' xs 0 where length' [] n = n length' (x:xs) n = length xs (n + 1) doesn't suffer from this problem, but I don't understand how this can run in constant space in a lazy language. Isn't the runtime accumulating numerous (n + 1) thunks as it moves through the list? Shouldn't this function Haskell to consume O(n) space and lead to stack overflow? (if it matters, I'm using GHC)

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  • JPA : Inheritance - Discriminator value not taken into account in generated SQL

    - by Julien
    I try to use this mapping : @Entity @Table(name="ecc.\"RATE\"") @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(name="DISCRIMINATOR", discriminatorType= DiscriminatorType.STRING) public abstract class Rate extends GenericBusinessObject { ... } @Entity @DiscriminatorValue("E") public class EntranceRate extends Rate { @ManyToOne @JoinColumn(name = "\"RATES_GRID_ID\"") protected RatesGrid ratesGrid; ... } @Entity @Table(name="ecc.\"RATES_GRID\"") public class RatesGrid extends GenericBusinessObject { /** */ @OneToMany(mappedBy = "ratesGrid", targetEntity = EntranceRate.class, fetch=FetchType.LAZY) private List<EntranceRate> entranceRates; } When I try to access my entranceRates list from a ratesGrid object, I get this error : Object with id: 151 was not of the specified subclass: com.ecc.bo.rate.EntranceRate (loaded object was of wrong class class com.ecc.bo.rate.AnnualRate) Looking at the sql generated, I found no trace of "discriminator=" in the where clause. What am I doing wrong ? I use a PostGreSQL database and a Hibernate as JPA provider.

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  • VS2012 equivalent of Eclipse's default Ctrl-Shift-O?

    - by x3chaos
    I'm used to Java (in Eclipse), which has its import statements, but I'm writing a DLL in Visual C# (in Visual Studio 2012), which has its using statements. I'm used to Eclipse's default keyboard shortcut Ctrl-Shift-O, which updates the list of import statements in the Java perspective, deleting unused imports and adding necessary imports found on the build path. Is there an equivalent operation in VS2012 with VC#? I've just been selecting the word, opening the Office-style popup, and added the "using" statement that way, but it conflicts with my workflow (read: I'm lazy and I like having my shortcuts).

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  • Nibernate, DynamicProxy, and Spring AOP

    - by jeff
    We have an Spring IOC managed application that uses NHibernate in its persistence layer. We have use the Spring AOP and understand its terminology and capabilities. We have some investment in Spring proxies. Now, we want to add a PropertyChangedMixin and a ValidatorInterceptor (not nhibernate validator, but based on Spring validation) onto our NHibernate managed objects. I've looked at the hooks for NHiberate IInterceptor and EventListeners and that gives me a place to apply the desired proxies. If I use the Spring proxies is it going to play nice with the existing nhibernate proxies. We don't lazy load. From the simple nhibernate stuff the benefits of DynamicProxy look appealing. I can go either way, but I'd like to hear suggestions. Thanks, jeff

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  • streaming XML serialization in .net

    - by Luca Martinetti
    Hello, I'm trying to serialize a very large IEnumerable<MyObject> using an XmlSerializer without keeping all the objects in memory. The IEnumerable<MyObject> is actually lazy.. I'm looking for a streaming solution that will: Take an object from the IEnumerable<MyObject> Serialize it to the underlying stream using the standard serialization (I don't want to handcraft the XML here!) Discard the in memory data and move to the next I'm trying with this code: using (var writer = new StreamWriter(filePath)) { var xmlSerializer = new XmlSerializer(typeof(MyObject)); foreach (var myObject in myObjectsIEnumerable) { xmlSerializer.Serialize(writer, myObject); } } but I'm getting multiple XML headers and I cannot specify a root tag <MyObjects> so my XML is invalid. Any idea? Thanks

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  • WCF DataContract deserialization of complex types

    - by Meidan Alon
    Hi, I have a service that returns a collection of MyClass objects. If all of the MyClass instances have null in MyClass2Reference then everything works fine. Otherwise, I get a "Connection reset" error on the client side. What am I doing wrong? Nevrmind: was a problem with NHibernate lazy proxy objects. [DataContract] public MyClass { [DataMember] int ID; [DataMember] MyClass2 MyClass2Reference; } [DataContract] public MyClass2 { [DataMember] int ID; [DataMember] string Name; }

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  • CODE1 at SPOJ - cannot solve it

    - by VaioIsBorn
    I am trying to solve the problem Secret Code on SPOJ, and it's obviously a math problem. The full problem For those who are lazy to go and read, it's like this: a0, a1, a2, ..., an - sequence of N numbers B - a Complex Number (has both real and imaginary components) X = a0 + a1*B + a2*(B^2) + a3*(B^3) + ... + an*(B^n) So if you are given B and X, you should find a0, a1, ..an. I don't know how or where to start, because not even N is known, just X and B. The problem is not as easy as expressing a number in a base B, because B is a complex number. How can it be solved?

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  • Entity Framework associations killing performance

    - by Chris
    Here is the performance test i am looking at. I have 8 different entities that are table per type. Some of the entities contain over 100 thousand rows. This particular application does several recursive calculations on the client so I think it may be best to preload the data instead of lazy loading. If there are no associations I can load the entire database in about 3 seconds. As I add associations in any way the performance starts to drastically decline. I am loading all the data the same way (just calling toList() on the entity attached to the context). I ran the test with edmx generated classes and self tracking entities and had similar results. I am sure if I were to try and deal with the associations myself, similar to how I would in a dataset, the performance problem would go away. On the other hand I am pretty sure this is not how the entity framework was intended to being used. Any thoughts or ideas?

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  • How to scroll and zoom in/out large images on iPhone?

    - by Horace Ho
    I have a large image, size around 30000 (w) x 6000 (h) pixels. You may consider it's like a big map. I assume I need to crop it up into smaller tiles. Questions: what are the right ViewControllers to use? (link) what is the tile strategy? (I put this in another question, as it's not iPhone specific) Requirements: whole image (though cropped) can be scrolled up/down/left/right by swipes zoom in (up to pixel-to-pixel) out (down to screen-fit-by-height) by the 2-finger operation memory efficiency by lazy loading tiles Bonus requirements: automatic scroll, say from left to right slowly and smoothly Thanks!

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  • Joomla template parameters and params.ini - file becomes unwritable after save.

    - by Moak
    I am using wamp and creating a Joomla template with changeable parameters. initially the message is The parameter file \templates\ssc_2010\params.ini is writable! once I make changes everything works as expected, except now i get the message: The parameter file \templates\ssc_2010\params.ini is unwritable! One solution is to brows to the directory, right click the file, select properties, and uncheck read-only. Again the file is writable but once I modify the parameters again it becomes read only again. I'm quite lazy and would like to prevent this from happening again, I've notice this happening in past projects, but now I have to work a lot with parameters so it becomes quite boring doing manual labor like that :P

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  • Any clever way to fix 'string or binary data would be truncated' warning with LINQ

    - by Simon_Weaver
    Is there a clever way to determine which field is causing 'string or binary data would be truncated' with LINQ. I've always ended up doing it manually by stepping through a debugger, but with a batch using 'SubmitChanges' I have to change my code to inserting a single row to find the culprit in a batch of rows. Am I missing something or in this day and age do I really have to still use a brute force method to find the problem. Please dont give me advice on avoiding this error in future (unless its something much cleverer than 'validate your data'). The source data is coming from a different system where I dont have full control anyway - plus I want to be lazy. PS. Does SQL Server 2008 actually tell me the field name. Please tell me it does! I'll upgrade!

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  • Auto-generate WebControls

    - by Adrian K
    I want to generate .net code from a template so that it more rapid, so lazy developers (and I mean that in the nicest possible way!) don't have to write them in the IDE, compile them, etc... I know I can roll my own tool which generates the code using reflection (by reading in some text file, etc), but I just wondered if there was an easier than starting from scratch since this is what ASP.NET basically does already; so is there anyway to leverage this? E.g. to quote Peter A. Bromberg: Even an ASPX page with no code on it gets turned into an instance of the System.Web.UI.Page class. The page is parsed by the ASP.NET engine when it is first requested, and then its JIT compiled version is cached in the Temporary ASP.NET Files folder as long as the application is running and the .aspx page hasn't been changed. Ideally I want to auto-generate WebControls, but examples of anything closely related will do. C# Examples preferred also, but anything considered :)

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  • creating PHP C/C++ extension modules using SWIG

    - by morpheous
    I have written some C/C++ extension modules for PHP, using the 'old fashioned way' - i.e. by using the manual way (as described by Sarah Golemon in her book). This is too fiddly for me, and since I am lazy, and would like to automate as much as possible. Also, I have used SWIG now to generate extensions to Python, and I am getting to like using it quite a lot. I am thinking of using SWIG to generate my future PHP extensions. I am using PHP v5.2 (and above) on my production servers. My questions are: Is SWIG PHP interface stable yet (i.e. ready for production)? If you answered yes to question 1 -are YOU using it in YOUR production site? Are there any 'gotchas' I need to be aware of when creating PHP extension ,modules using SWIG?

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  • Scala simple dummy project.

    - by Lukasz Lew
    Currently my whole work cycle is: edit foo.scala fsc foo.scala && scala -cp . FooMain But my project is getting bigger and I would like to split files, make unit tests, etc. But I'm too lazy for reading sbt documentation and doing whatever needs to be done to get a sbt's "Makefile". Similarly for unit tests (there are so many frameworks, which to choose?) What would make my day is a simple zipped dummy project with a dummy unit tests using sbt. Do you know whether such thing exists?

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  • How do I create a Launcher in Ubuntu 9.1 that runs a shell script?

    - by mkelley33
    Here's my situation: New to Ubuntu (just nstalled 9.10 Karmic Koala 64 bit) Purpose: to easily run PyCharm without too much typing (ie. cd... ./pycharm.sh) Want to create desktop Launcher instead of terminal & typing (without resorting to the "Run in Terminal" option) Tried to create Launcher to executes .sh script in Document directory Right-clicked Desktop Create Launcher a. Type == Application; Browse [insert absolute path to .sh script]; no luck b. Type == Application in Terminal; Browse ...ditto I'm open to any other alternatives that involve as little typing as possible. I would like to just start Ubuntu, click Launcher icons, and have terminals spring to life, running the intended scripts. Crazy? No. Lazy? Probably. Productive? Hopefully :)

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  • Git remove directory

    - by hrickards
    I've got a repository on GitHub (http://github.com/hrickards/PHP-Crypto) for a little project me and a couple of others are working on. My development environment is Aptana Studio, and I use the EGit plugin as Aptana is basically Eclipse underneath. Today the designer sent the HTML and CSS for the website with the images in a folder named img. Previously the images were in a folder called images. Thinking nothing of it and being too lazy to update the CSS and HTML, I simply kept the images in the img directory and commited to Git. However, the GitHub web interface shows both the img and images directories, with the images directory being empty. I've tried deleting the images directory with git rm -r images and git rm images, and even mkdir images; git add images; git rm -r images but whatever I try I get the same result: fatal: pathspec 'images' did not match any files. Has anyone got any advice on how to remove images, or am I misunderstanding Git or something?

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  • When are you truly forced to use UUID as part of the design?

    - by Pyrolistical
    I don't really see the point of UUID. I know the probability of a collision is effectively nil, but effectively nil is not even close to impossible. Can somebody give an example where you have no choice but to use UUID? From all the uses I've seen, I can see an alternative design without UUID. Sure the design might be slightly more complicated, but at least it doesn't have a non-zero probability of failure. UUID smells like global variables to me. There are many ways global variables make for simpler design, but its just lazy design.

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  • flex/actionscript client entity state refresh on JPA update using Pimento EntityManager

    - by Chris
    My Flex application uses a client-side pimento EntityManager which fetches quite a few objects and associations. It does this by forcing eager fetching of particular association ends in the form of fetch plans. I would like to update the client whenever a change has been made to an entity existing in the EntityManager's cache. Is it possible to update the state of the changed entity ONLY, including updating which entities are associated, without resetting the state of these associated entities? I have setup an EntityListener with a JPA post-update method that notifies clients when a persisted entity has been updated. I want this to trigger a refresh for the modified client-side entity, but calling EntityManager.refresh(entity) resets all lazy associations to proxies. Initializing these proxies resets the associated entities, even if they were loaded previously. I'm looking for an efficient way to keep the client's state in synch with the server's state, at least with respect to the entities that have already been retrieved by the initial load.

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  • NHibernate bag is always null

    - by Neville Chinan
    I have set up my mapping file and classes as suggested by many articles class A { ... IList BBag {get;set;} ... } class B { ... A aObject {get;set;} ... } <class name="A">...<bag name="BBag" table="B" inverse="true" lazy="false"><key column="A_ID" /><one-to-many class="B" /></bag>... <class name="B">...<many-to-one name="aObject" class="A" column="A_ID" />... I added a set of A's to the A table and a set of B's to the B table, all the data is stored as expected. However if I try and access aInstance.BBag.Count I get a null reference exception. I think I missing some key knowledge on how an bag gets instantiated. Thanks

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  • Joomla Template Parameters and params.ini

    - by Moak
    I am using wamp and creating a Joomla template with changeable parameters. initially the message is The parameter file \templates\ssc_2010\params.ini is writable! once I make changes everything works as expected, except now i get the message: The parameter file \templates\ssc_2010\params.ini is unwritable! One solution is to brows to the directory, right click the file, select properties, and uncheck read-only. Again the file is writable but once I modify the parameters again it becomes read only again. I'm quite lazy and would like to prevent this from happening again, I've notice this happening in past projects, but now I have to work a lot with parameters so it becomes quite boring doing manual labor like that :P

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  • How to handle an "infinite" IEnumerable?

    - by Danvil
    A trivial example of an "infinite" IEnumerable would be IEnumerable<int> Numbers() { int i=0; while(true) { yield return i++; } } I know, that foreach(int i in Numbers().Take(10)) { Console.WriteLine(i); } and var q = Numbers(); foreach(int i in q.Take(10)) { Console.WriteLine(i); } both work fine (and print out the number 0-9). But are there any pitfalls when copying or handling expressions like q? Can I rely on the fact, that they are always evaluated "lazy"? Is there any danger to produce an infinite loop?

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  • Is there a SQL Server error numbers C# wrapper anyone knows of?

    - by Mr Grok
    I really want to do something useful when a PK violation occurs but I hate trapping error numbers... they just don't read right without comments (they're certainly not self documenting). I know I can find all the potential error numbers at SQL Server books online but I really want to be able to pass the error number to some helper class or look it up against a Dictionary of some sort rather than have non-descript err numbers everywhere. Has anyone got / seen any code anywhere that encapsulates the SQL Server Error numbers in this way as I don't want to re-invent the wheel (or I'm lazy maybe).

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  • Why does dojo parsing time depend on css and images availability?

    - by Kniganapolke
    I have been profiling javascript on my page that uses dojo widgets. I don't use explicit parsing - the parser runs on page load. What I noticed is that if I clear browser cache before refreshing the page, dojo parsing takes much more time than if all the files are already cached. Note that we build all the required dojo modules into a layer (a single file), so we don't lazy-load any js files. I wonder if dojo parsing process depends on images and css resources, as far as I know it only instantiates widgets and injects dom nodes. Do you have any ideas why dojo parser runs longer (2-3 times longer in my case) when the cache is cleared?

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  • Method hiding with interfaces

    - by fearofawhackplanet
    interface IFoo { int MyReadOnlyVar { get; } } class Foo : IFoo { int MyReadOnlyVar { get; set; } } public IFoo GetFoo() { return new Foo { MyReadOnlyVar = 1 }; } Is the above an acceptable way of implementing a readonly/immutable object? The immutability of IFoo can be broken with a temporary cast to Foo. In general (non-critical) cases, is hiding functionality through interfaces a common pattern? Or is it considered lazy coding? Or even an anti-pattern?

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  • Clojure: Avoiding stack overflow in Sieve of Erathosthene?

    - by nixx
    Here's my implementation of Sieve of Erathosthene in Clojure (based on SICP lesson on streams): (defn nats-from [n] (iterate inc n)) (defn divide? [p q] (zero? (rem q p))) (defn sieve [stream] (lazy-seq (cons (first stream) (sieve (remove #(divide? (first stream) %) (rest stream)))))) (def primes (sieve (nats-from 2))) Now, it's all OK when i take first 100 primes: (take 100 primes) But, if i try to take first 1000 primes, program breaks because of stack overflow. I'm wondering if is it possible to change somehow function sieve to become tail-recursive and, still, to preserve "streamnes" of algorithm? Any help???

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