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  • How do I serialise a graph in Java without getting StackOverflowException?

    - by Tim Cooper
    I have a graph structure in java, ("graph" as in "edges and nodes") and I'm attempting to serialise it. However, I get "StackOverflowException", despite significantly increasing the JVM stack size. I did some googling, and apparently this is a well known limitation of java serialisation: that it doesn't work for deeply nested object graphs such as long linked lists - it uses a stack record for each link in the chain, and it doesn't do anything clever such as a breadth-first traversal, and therefore you very quickly get a stack overflow. The recommended solution is to customise the serialisation code by overriding readObject() and writeObject(), however this seems a little complex to me. (It may or may not be relevant, but I'm storing a bunch of fields on each edge in the graph so I have a class JuNode which contains a member ArrayList<JuEdge> links;, i.e. there are 2 classes involved, rather than plain object references from one node to another. It shouldn't matter for the purposes of the question). My question is threefold: (a) why don't the implementors of Java rectify this limitation or are they already working on it? (I can't believe I'm the first person to ever want to serialise a graph in java) (b) is there a better way? Is there some drop-in alternative to the default serialisation classes that does it in a cleverer way? (c) if my best option is to get my hands dirty with low-level code, does someone have an example of graph serialisation java source-code that can use to learn how to do it?

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  • check properties of two objects for changes

    - by k-hoffmann
    Hi, i have to develop a mechanism to check two object properties for changes. All properties which are needed to check are marked with an attribute. Atm i - read all properties from acutal object via linq - read the corresponding property from old object - fill an own object with the two properties (old and new value) In Code the call to the workerclass looks like this public void CreateHistoryMap(BaseEntity actual, BaseEntity old) { CreateHistoryMap(actualEntity, oldEntity) .ForEach(mapEntry => CreateHistoryEntry(mapEntry), mapEntry => IfChangesDetected(mapEntry)); } CreateHistoryMap builds up the HistoryMapEntry which contains the two properties. CreateHistoryEntry build up the object which is saved to database, the IfChangesDetected check the object for changes. I have to handle own special application types to generate history values to database (like concatinating list values and so on). My problem is now, that i have to read the values of the properties twice - for change detection - and for the concreate CreateHistoryEntry How can i eliminate this problem or how can i implement the change tracking scenario with the nice c# 3.5 features? Thanks a lot.

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  • rails not recognizing project

    - by tipu
    I can create a new project using rails and I can use stuff like rails migration ... and i (correctly) get a error because the sqlite gem is missing. but when i try using rails migration ... with a project i checked out from github, it doesn't recognize that it is a rails project i get: Usage: rails new APP_PATH [options] Options: -d, [--database=DATABASE] # Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db) # Default: sqlite3 -O, [--skip-active-record] # Skip Active Record files [--dev] # Setup the application with Gemfile pointing to your Rails checkout -J, [--skip-prototype] # Skip Prototype files -T, [--skip-test-unit] # Skip Test::Unit files -G, [--skip-git] # Skip Git ignores and keeps -b, [--builder=BUILDER] # Path to an application builder (can be a filesystem path or URL) [--edge] # Setup the application with Gemfile pointing to Rails repository -m, [--template=TEMPLATE] # Path to an application template (can be a filesystem path or URL) -r, [--ruby=PATH] # Path to the Ruby binary of your choice # Default: /usr/bin/ruby1.8 [--skip-gemfile] # Don't create a Gemfile and it goes on. any ideas? edit: it's probably an important detail that earlier my rails wasn't working at all. i had to cp /usr/bin/ruby to /usr/bin/local/ruby

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  • Type classe, generic memoization

    - by nicolas
    Something quite odd is happening with y types and I quite dont understand if this is justified or not. I would tend to think not. This code works fine : type DictionarySingleton private () = static let mutable instance = Dictionary<string*obj, obj>() static member Instance = instance let memoize (f:'a -> 'b) = fun (x:'a) -> let key = f.ToString(), (x :> obj) if (DictionarySingleton.Instance).ContainsKey(key) then let r = (DictionarySingleton.Instance).[key] r :?> 'b else let res = f x (DictionarySingleton.Instance).[key] <- (res :> obj) res And this ones complains type DictionarySingleton private () = static let mutable instance = Dictionary<string*obj, _>() static member Instance = instance let memoize (f:'a -> 'b) = fun (x:'a) -> let key = f.ToString(), (x :> obj) if (DictionarySingleton.Instance).ContainsKey(key) then let r = (DictionarySingleton.Instance).[key] r :?> 'b else let res = f x (DictionarySingleton.Instance).[key] <- (res :> obj) res The difference is only the underscore in the dictionary definition. The infered types are the same, but the dynamic cast from r to type 'b exhibits an error. 'this runtime coercition ... runtime type tests are not allowed on some types, etc..' Am I missing something or is it a rough edge ?

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  • Can C++ do something like an ML case expression?

    - by Nathan Andrew Mullenax
    So, I've run into this sort of thing a few times in C++ where I'd really like to write something like case (a,b,c,d) of (true, true, _, _ ) => expr | (false, true, _, false) => expr | ... But in C++, I invariably end up with something like this: bool c11 = color1.count(e.first)>0; bool c21 = color2.count(e.first)>0; bool c12 = color1.count(e.second)>0; bool c22 = color2.count(e.second)>0; // no vertex in this edge is colored // requeue if( !(c11||c21||c12||c22) ) { edges.push(e); } // endpoints already same color // failure condition else if( (c11&&c12)||(c21&&c22) ) { results.push_back("NOT BICOLORABLE."); return true; } // nothing to do: nodes are already // colored and different from one another else if( (c11&&c22)||(c21&&c12) ) { } // first is c1, second is not set else if( c11 && !(c12||c22) ) { color2.insert( e.second ); } // first is c2, second is not set else if( c21 && !(c12||c22) ) { color1.insert( e.second ); } // first is not set, second is c1 else if( !(c11||c21) && c12 ) { color2.insert( e.first ); } // first is not set, second is c2 else if( !(c11||c21) && c22 ) { color1.insert( e.first ); } else { std::cout << "Something went wrong.\n"; } I'm wondering if there's any way to clean all of those if's and else's up, as it seems especially error prone. It would be even better if it were possible to get the compiler complain like SML does when a case expression (or statement in C++) isn't exhaustive. I realize this question is a bit vague. Maybe, in sum, how would one represent an exhaustive truth table with an arbitrary number of variables in C++ succinctly? Thanks in advance.

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  • What algorithms compute directions from point A to point B on a map?

    - by A. Rex
    How do map providers (such as Google or Yahoo! Maps) suggest directions? I mean, they probably have real-world data in some form, certainly including distances but also perhaps things like driving speeds, presence of sidewalks, train schedules, etc. But suppose the data were in a simpler format, say a very large directed graph with edge weights reflecting distances. I want to be able to quickly compute directions from one arbitrary point to another. Sometimes these points will be close together (within one city) while sometimes they will be far apart (cross-country). Graph algorithms like Dijkstra's algorithm will not work because the graph is enormous. Luckily, heuristic algorithms like A* will probably work. However, our data is very structured, and perhaps some kind of tiered approach might work? (For example, store precomputed directions between certain "key" points far apart, as well as some local directions. Then directions for two far-away points will involve local directions to a key points, global directions to another key point, and then local directions again.) What algorithms are actually used in practice? PS. This question was motivated by finding quirks in online mapping directions. Contrary to the triangle inequality, sometimes Google Maps thinks that X-Z takes longer and is farther than using an intermediate point as in X-Y-Z. But maybe their walking directions optimize for another parameter, too? PPS. Here's another violation of the triangle inequality that suggests (to me) that they use some kind of tiered approach: X-Z versus X-Y-Z. The former seems to use prominent Boulevard de Sebastopol even though it's slightly out of the way. (Edit: this example doesn't work anymore, but did at the time of the original post. The one above still works as of early November 2009.)

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  • This is a great job opportunity!!! [closed]

    - by Stuart Gordon
    ASP.NET MVC Web Developer / London / £450pd / £25-£50,000pa / Interested contact [email protected] ! As a web developer within the engineering department, you will work with a team of enthusiastic developers building a new ASP.NET MVC platform for online products utilising exciting cutting edge technologies and methodologies (elements of Agile, Scrum, Lean, Kanban and XP) as well as developing new stand-alone web products that conform to W3C standards. Key Responsibilities and Objectives: Develop ASP.NET MVC websites utilising Frameworks and enterprise search technology. Develop and expand content management and delivery solutions. Help maintain and extend existing products. Formulate ideas and visions for new products and services. Be a proactive part of the development team and provide support and assistance to others when required. Qualification/Experience Required: The ideal candidate will have a web development background and be educated to degree level in a Computer Science/IT related course plus ASP.NET MVC experience. The successful candidate needs to be able to demonstrate commercial experience in all or most of the following skills: Essential: ASP.NET MVC with C# (Visual Studio), Castle, nHibernate, XHTML and JavaScript. Experience of Test Driven Development (TDD) using tools such as NUnit. Preferable: Experience of Continuous Integration (TeamCity and MSBuild), SQL Server (T-SQL), experience of source control such as Subversion (plus TortioseSVN), JQuery. Learn: Fluent NHibernate, S#arp Architecture, Spark (View engine), Behaviour Driven Design (BDD) using MSpec. Furthermore, you will possess good working knowledge of W3C web standards, web usability, web accessibility and understand the basics of search engine optimisation (SEO). You will also be a quick learner, have good communication skills and be a self-motivated and organised individual.

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  • Common "truisms" needing correction the most

    - by Charles Bretana
    In addition to "I never met a man I didn't like", Will Rogers had another great little ditty I've always remembered. It went: "It's not what you don't know that'll hurt you, it's what you do know that ain't so." We all know or subscribe to many IT "truisms" that mostly have a strong basis in fact, in something in our professional careers, something we learned from others, lessons learned the hard way by ourselves, or by others who came before us. Unfortuntely, as these truisms spread throughout the community, the details—why they came about and the caveats that affect when they apply—tend to not spread along with them. We all have a tendency to look for, and latch on to, small "rules" or principles that we can use to avoid doing a complete exhaustive analysis for every decision. But even though they are correct much of the time, when we sometimes misapply them, we pay a penalty that could be avoided by understooding the details behind them. For example, when user-defined functions were first introduced in SQL Server it became "common knowledge" within a year or so that they had extremely bad performance (because it required a re-compilation for each use) and should be avoided. This "trusim" still increases many database developers' aversion to using UDFs, even though Microsoft's introduction of InLine UDFs, which do not suffer from this issue at all, mitigates this issue substantially. In recent years I have run into numerous DBAs who still believe you should "never" use UDFs, because of this. What other common not-so-"trusims" do you know, which many developers believe, that are not quite as universally true as is commonly understood, and which the developer community would benefit from being better educated about? Please include why it was "true" to start off with, and under what circumstances it's not true. Limit responses to issues that are technical, where the "common" application of a "rule or principle" is in fact correct most of the time, or was correct back when it was first elucidated, but—in the edge cases, or because of not understanding the principle thoroughly, because technology has changed since it first spread, or applying the rule today without understanding the details behind the rule—can easily backfire or cause the opposite of the intended effect.

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  • Move camera to fit 3D scene

    - by Burre
    Hi there. I'm looking for an algorithm to fit a bounding box inside a viewport (in my case a DirectX scene). I know about algorithms for centering a bounding sphere in a orthographic camera but would need the same for a bounding box and a perspective camera. I have most of the data: I have the up-vector for the camera I have the center point of the bounding box I have the look-at vector (direction and distance) from the camera point to the box center I have projected the points on a plane perpendicular to the camera and retrieved the coefficients describing how much the max/min X and Y coords are within or outside the viewing plane. Problems I have: Center of the bounding box isn't necessarily in the center of the viewport (that is, it's bounding rectangle after projection). Since the field of view "skew" the projection (see http://en.wikipedia.org/wiki/File:Perspective-foreshortening.svg) I cannot simply use the coefficients as a scale factor to move the camera because it will overshoot/undershoot the desired camera position How do I find the camera position so that it fills the viewport as pixel perfect as possible (exception being if the aspect ratio is far from 1.0, it only needs to fill one of the screen axis)? I've tried some other things: Using a bounding sphere and Tangent to find a scale factor to move the camera. This doesn't work well, because, it doesn't take into account the perspective projection, and secondly spheres are bad bounding volumes for my use because I have a lot of flat and long geometries. Iterating calls to the function to get a smaller and smaller error in the camera position. This has worked somewhat, but I can sometimes run into weird edge cases where the camera position overshoots too much and the error factor increases. Also, when doing this I didn't recenter the model based on the position of the bounding rectangle. I couldn't find a solid, robust way to do that reliably. Help please!

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  • jQuery resizable() dynamic maxWidth option

    - by Vitaliy Isikov
    I have 3 columns that are resizable. When one is made wider, the one to it's left is made smaller. Essentially there are only 2 handles. Left col and Mid col. So when Mid col is made thinner, Right col expands accordingly. All three of them are contained with a 900px parent div, so the sum of all three is always 900. They have max and min widths set statically. My issue is that if you take the left handle and move it all the way to the right you're still able to use the right handle and expand the mid col past the edge of the parent div. I thought of a way to solve that issue by writing up a function that checks the widths of the columns and then subtracts left and right columns from the parent div width, I called it mWid. This leaves me with the number I want to set as the maxWidth for Mid col. Now the issue is that mWid is not gettings updated for here "maxWidth: mWid" Here is what the function for the right handle looks like: $(function() { $("#midResizable").resizable({ handles: 'e', containment: '#container', maxWidth: mWid, // gets set once, but doesn't update! WHY? minWidth: 195, resize: function(event, ui) { contWidth = $('#container').width() newWidth = $(this).width() leftWidth = $('#leftResizable').width() rightWidth = $('#rightResizable').width() $("#rightResizable").css("width", (contWidth-15)-(newWidth)-(leftWidth)+"px"); checkWid() } }); }); function checkWid() { rightWidth = $('#rightResizable').width() leftWidth = $('#leftResizable').width() contWidth = $('#container').width() mWid = (contWidth-15)-(rightWidth)-(leftWidth) }

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  • How to make use of Grails Dependencies in your IDE

    - by raoulsson
    Hi All, So I finally got my dependencies working with Grails. Now, how can my IDE, eg IntelliJ or Eclipse, take advantage of it? Or do I really have to manually manage what classes my IDE knows about at "development time"? If the BuildConfig.groovy script is setup right (see here), you will be able to code away with vi or your favorite editor without any troubles, then run grails compile which will resolve and download the dependencies into the Ivy cache and off you go... If, however, you are using an IDE like Eclipse or IntelliJ, you will need the dependencies at hand while coding. Obviously - as these animals will need them for the "real time" error detection/compilation process. Now, while it is certainly possible to code with all the classes shining up in bright red all over the place that are unknown to your IDE, it is certainly not much fun... The Maven support or whatever it is officially called lives happily with the pom file, no extra "jar directory" pointers needed, at least in IntelliJ. I would like to be able to do the same with Grails dependencies. Currently I am defining them in the BuildConfig.groovy and additionally I copy/paste the current jars around on my local disk and let the IDE point to it. Not very satisfactory, as I am working in a highly volatile project module environment with respect to code change. And this situation ports me directly into "jar hell", as my "develop- and build-dependencies" easily get out of sync and I have to manage manually, that is, with my brain... And my brain should be busy with other stuff... Thanks! Raoul P.S: I'm currently using Grails 1.2M4 and IntelliJ 92.105. But feel free to add answers on future versions of Grails and different, future IDEs, as the come in...

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  • Is it rude to add "TODO: wtf?" in source code?

    - by mafutrct
    I encountered something ... well, you know TDWTF... something like that in an international project I'm working on. The code was written by a team mate. For a second I was tempted to add // TODO: wtf? to the infringing code but restrained myself. The project is indeed on a professional level, but for internal conversation, more colloquial language is used - but still no "bad" words as in "wtf". Usually, I'd surely not add such a comment, but I believe there are a few factors that allow consideration still: 1. It is not visible except as a comment in the source code (of course). 2. It is internal to our team - other developers may happen see it but it is not their code. 3. Comments in source code are usually accepted to be more colloquial, since it is "kept between us developers". Would you totally advise to never add such a comment? Or do you regard it as an edge case? Did you possibly add something similar yourself?

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  • Concept: Is mongo right for applying schemas?

    - by Jan
    I am currently in charge of checking wether it is valuable for one of our upcoming products to be developed on mongo. Without going too much into detail, I'll try to explain, what the app does. The app simply has "entities". These entities are technical stuff, like cell phones, TVs, Laptops, tablet pcs, and so forth. Of course, a cell phone has other attributes than a Tablet PCs and a Laptop has even other attributes, like RAM, CPU, display size and so on. Now I want to have something that we wanna call a scheme: We define that we need to have saved the display size, amount of ram size of flash devices, processor type, processor speed and so on for tablet pcs. For cell phone we might save display size, GSM, Edge, 3g, 4g, processor, ram, touch screen technology, bla bla bla. I think you got it :) What I want to realize is, that each "category" has a schema and when one of the system's users enters a new product (let's say the new iphone 4), the app constructs the form to be filled out with the appropriate attributes. So far it sounds nice and should not be a problem with mongo. But now the tough for which I could not find a clean solution.... An attribute modeled in mongo looks like: { _id: 1234456, name: "Attribute name", type: 0, "description" } But what to do, if i need this attribute in several languages, like: { en: {name: "Attribute name", type: 0, "description"}, de: {name: "Name des Attributs, type: 0, "Beschreibung"} } I also need to ensure that the german attribute gets updated as soon as the english gets updated, for instance when type changes from 0 to 1. Any ideas on that?

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  • C++ Memory Leak, Can't find where

    - by Nicholas
    I'm using Visual Studio 2008, Developing an OpenGL window. I've created several classes for creating a skeleton, one for joints, one for skin, one for a Body(which is a holder for several joints and skin) and one for reading a skel/skin file. Within each of my classes, I'm using pointers for most of my data, most of which are declared using = new int[XX]. I have a destructor for each Class that deletes the pointers, using delete[XX]. Within my GLUT display function I have it declaring a body, opening the files and drawing them, then deleting the body at the end of the display. But there's still a memory leak somewhere in the program. As Time goes on, it's memory usage just keep increasing, at a consistent rate, which I'm interpreting as something that's not getting deleted. I'm not sure if it's something in the glut display function that's just not deleting the Body class, or something else. I've followed the steps for memory leak detection in Visual Studio 2008 and it doesn't report any leak, but I'm not 100% sure if it's working right for me. I'm not fluent in C++, so there maybe something I'm overlooking, can anyone see it?

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  • In Varnish, how can I read the Set-Cookie response header?

    - by Adam Friedman
    I am trying to detect if my application has set a cookie that holds an "alert message" for the user on the next page, where the Javascript displays it if detected. In my vcl_fetch(), I need to detect if the specific cookie value "alert_message" appears anywhere in the Set-Cookie header (presumably in the VCL variable beresp.http.Set-Cookie). If detected, then I do not want to cache that next page (since Varnish strips the Set-Cookie header by default, which would obliterate the alert message before it makes it back to the browser). So here is my simple test: if(beresp.http.Set-Cookie ~ "alert_message") { set req.http.no_cache = 1; } Strangely, it fails to evaluate to true. So I throw the variable into the Server header to see what it looks like: set beresp.http.Server = " MyApp Varnish implementation - test reading set-cookie: "+beresp.http.Set-Cookie; But for some reason this only displays the FIRST Set-Cookie line in the response headers. Here are the relevant response headers: Server: MyApp Varnish implementation - test reading cookie: elstats_session=7d7279kjmsnkel31lre3s0vu24; expires=Wed, 10-Oct-2012 00:03:32 GMT; path=/; HttpOnly Set-Cookie:app_session=7d7279kjmsnkel31lre3s0vu24; expires=Wed, 10-Oct-2012 00:03:32 GMT; path=/; HttpOnly Set-Cookie:alert_message=Too+many+results.; expires=Tue, 09-Oct-2012 20:13:32 GMT; path=/; domain=.my.app.com Set-Cookie:alert_key=flash_error; expires=Tue, 09-Oct-2012 20:13:32 GMT; path=/; domain=.my.app.com Vary:Accept-Encoding How do I read and run string detection on ALL Set-Cookie header lines?

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  • How can I find out if the MainActivity is being paused from my Java class?

    - by quinestor
    I am using motion sensor detection in my application. My design is this: a class gets the sensor services references from the main activity and then it implements SensorEventListener. That is, the MainActivity does not listen for sensor event changes: public void onCreate(Bundle savedInstanceState) { // ... code mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE); mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); // The following is my java class, it does not extends any android fragment/activty mShakeUtil = new ShakeUtil(mSensorManager,mAccelerometer,this); // ..more code.. } I can't redesign ShakeUtil so it is a fragment nor activity, unfortunately. Now to illustrate the problem consider: MainActivity is on its way to be destroyed/paused. I.e screen rotation ShakeUtil's onSensorChanged(SensorEvent event) gets called in the process.. One of the things that happen inside onSensorChanged is a dialog interaction, which gives the error: java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState When the previous happens between MainActivity's onSaveInstanceState and onPause. I know this can be prevented if I successfully detect that MainActivity is being pause in ShakeUtil. How can I detect that MainActivity is being paused or onSaveInstanceState was called from ShakeUtil? Alternatively, how can I avoid this issue without making Shakeutil extend activity? So far I have tried with flag variables but that isn't good enough, I guess these are not atomic operations. I tried using Activity's isChangingConfigurations(), but I get an undocummented "NoSuchMethodFound" error.. I am unregistering the sensors by calling ShakeUtil when onPause in main ACtivity

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  • Pre-formatting text to prevent reflowing

    - by mattjn
    I've written a fairly simple script that will take elements (in this case, <p> elements are the main concern) and type their contents out like a typewriter, one by one. The problem is that as it types, when it reaches the edge of the container mid-word, it reflows the text and jumps to the next line (like word wrap in any text editor). This is, of course, expected behavior; however, I would like to pre-format the text so that this does not happen. I figure that inserting <br> before the word that will wrap would be the best solution, but I'm not quite sure what the best way to go about doing that is that supports all font sizes and container widths, while also keeping any HTML tags intact. I figure something involving a hidden <span> element, adding text to it gradually and checking its width against the container width might be on the right track, but I'm not quite sure how to actually put this together. Any help or suggestions on better methods would be appreciated.

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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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  • Saving a single entity instead of the entire context - revisited

    - by nite
    I’m looking for a way to have fine grained control over what is saved using Entity Framework, rather than the whole ObjectContext.SaveChanges(). My scenario is pretty straight forward, and I’m quite amazed not catered for in EF – pretty basic in NHibernate and all other data access paradigms I’ve seen. I’m generating a bunch of data (in a WPF UI) and allowing the user to fine tune what is proposed and choose what is actually committed to the database. For the proposed entities I’m: getting a bunch of reference entities (eg languages) via my objectcontext, creating the proposed entities and assigning these reference entities to them (as navigation properties), so by virtue of their relationship to the reference entities they’re implicitly added to the objectconext Trying to create & save individual entites based on the proposed entities. I figure this should be really simple & trivial but everything I’ve tried I’ve hit a brick wall, either I set up another objectcontext & add just the entity I need (it then tries to add the whole graph and fails as it’s on another objectcontext). I’ve tried MergeOptions = NoTracking on my reference entities to try to get the Attach/AddObject not to navigate through these to create a graph, no avail. I've removed the navigation properties from the reference entities. I've tried AcceptAllChanges, that works but pretty useless in practice as I do still want to track & save other entities. In a simple test, I can create 2 of my proposed entities, AddObject the one I want to save and then Detach the one I dont then call SaveChanges, this works but again not great in practice. Following are a few links to some of the nifty ideas which in the end don’t help in the end but illustrate the complexity of EF for something so simple. I’m really looking for a SaveSingle/SaveAtomic method, and think it’s a pretty reasonable & basic ask for any DAL, letalone a cutting edge ORM. http://stackoverflow.com/questions/1301460/saving-a-single-entity-instead-of-the-entire-context www.codeproject.com/KB/architecture/attachobjectgraph.aspx?fid=1534536&df=90&mpp=25&noise=3&sort=Position&view=Quick&select=3071122&fr=1 bernhardelbl.spaces.live.com/blog/cns!DB54AE2C5D84DB78!238.entry

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  • C# wrapper for objects

    - by Haggai
    I'm looking for a way to create a generic wrapper for any object. The wrapper object will behave just like the class it wraps, but will be able to have more properties, variable, methods etc., for e.g. object counting, caching etc. Say the wrapper class be called Wrapper, and the class to be wrapped be called Square and has the constructor Square(double edge_len) and the properties/methods EdgeLength and Area, I would like to use it as follows: Wrapper<Square> mySquare = new Wrapper<Square>(2.5); /* or */ new Square(2.5); Console.Write("Edge {0} -> Area {1}", mySquare.EdgeLength, mySquare.Area); Obviously I can create such a wrapper class for each class I want to wrap, but I'm looking for a general solution, i.e. Wrapper<T> which can handle both primitive and compound types (although in my current situation I would be happy with just wrapping my own classes). Suggestions? Thanks.

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  • Limiting the width of a TextBlock in Silverlight

    - by Druzil
    The obvious MaxWidth gets ignored and the text in the "DisplayBox" TextBlock displays the whole text even if this text continues past the parent container controls (to the edge of the silverlight area. <win:HierarchicalDataTemplate x:Key="hierarchicalTemplate" ItemsSource="{Binding _children}"> <Border BorderThickness="0" BorderBrush="Orange" HorizontalAlignment="Stretch" Background="{Binding Converter={StaticResource BackgroundConverter}}"> <toolkit:DockPanel LastChildFill="True" Width="{Binding HeirarchyLevel, Converter={StaticResource WidthConverter}}" Height="20"> <Canvas toolkit:DockPanel.Dock="Right" Width="20" MouseLeftButtonUp="Arrow_MouseLeftButtonDown"> <Rectangle Width="20" Height="20" Fill="Transparent" /> <Line Stroke="Black" X1="5" Y1="10" X2="17" Y2="10" /> <Line Stroke="Black" X1="11" Y1="5" X2="17" Y2="10" /> <Line Stroke="Black" X1="11" Y1="15" X2="17" Y2="10" /> </Canvas> <Ellipse Canvas.Top="5" Width="10" Height="10" Fill="Green" toolkit:DockPanel.Dock="Right" MouseLeftButtonDown="Ellipse_MouseLeftButtonDown" /> <Canvas Width="Auto" Loaded="TextArea_Loaded"> <TextBlock Name="DisplayBox" FontFamily="Arial" FontSize="17" Foreground="Black" Width="Auto" Text="{Binding TaskName}" MouseLeftButtonUp="TextBlock_MouseLeftButtonUp" /> <TextBox Name="EditBox" FontFamily="Arial" FontSize="10" Foreground="Black" Height="20" Text="{Binding TaskName}" Visibility="Collapsed" LostFocus="TextBox_LostFocus" /> <Line Stroke="Black" X1="0" Y1="10" X2="202" Y2="10" Width="Auto" /> </Canvas> </toolkit:DockPanel> </Border> </win:HierarchicalDataTemplate>

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  • How do you prove a function works?

    - by glenn I.
    I've recently gotten the testing religion and have started primarily with unit testing. I code unit tests which illustrate that a function works under certain cases, specifically using the exact inputs I'm using. I may do a number of unit tests to exercise the function. Still, I haven't actually proved anything other than the function does what I expect it to do under the scenarios I've tested. There may be other inputs and scenarios I haven't thought of and thinking of edge cases is expensive, particularly on the margins. This is all not very satisfying to do me. When I start to think of having to come up with tests to satisfy branch and path coverage and then integration testing, the prospective permutations can become a little maddening. So, my question is, how can one prove (in the same vein of proving a theorem in mathematics) that a function works (and, in a perfect world, compose these 'proofs' into a proof that a system works)? Is there a certain area of testing that covers an approach where you seek to prove a system works by proving that all of its functions work? Does anybody outside of academia bother with an approach like this? Are there tools and techniques to help? I realize that my use of the word 'work' is not precise. I guess I mean that a function works when it does what some spec (written or implied) states that it should do and does nothing other than that. Note, I'm not a mathematician, just a programmer.

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  • NHibernate: What are child sessions and why and when should I use them?

    - by stefando
    In the comments for the ayende's blog about the auditing in NHibernate there is a mention about the need to use a child session:session.GetSession(EntityMode.Poco). As far as I understand it, it has something to do with the order of the SQL operation which session.Flush will emit. (For example: If I wanted to perform some delete operation in the pre-insert event but the session was already done with deleting operations, I would need some way to inject them in.) However I did not find documentation about this feature and behavior. Questions: Is my understanding of child sessions correct? How and in which scenarios should I use them? Are they documented somewhere? Could they be used for session "scoping"? (For example: I open the master session which will hold some data and then I create 2 child-sessions from the master one. I'd expect that the two child-scopes will be separated but the will share objects from the master session cache. Is this the case?) Are they first class citizens in NHibernate or are they just hack to support some edge-case scenarios? Thanks in advance for any info.

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  • Make function declarations based on function definitions

    - by Clinton Blackmore
    I've written a .cpp file with a number of functions in it, and now need to declare them in the header file. It occurred to me that I could grep the file for the class name, and get the declarations that way, and it would've worked well enough, too, had the complete function declaration before the definition -- return code, name, and parameters (but not function body) -- been on one line. It seems to me that this is something that would be generally useful, and must've been solved a number of times. I am happy to edit the output and not worried about edge cases; anything that gives me results that are right 95% of the time would be great. So, if, for example, my .cpp file had: i2cstatus_t NXTI2CDevice::writeRegisters( uint8_t start_register, // start of the register range uint8_t bytes_to_write, // number of bytes to write uint8_t* buffer = 0) // optional user-supplied buffer { ... } and a number of other similar functions, getting this back: i2cstatus_t NXTI2CDevice::writeRegisters( uint8_t start_register, // start of the register range uint8_t bytes_to_write, // number of bytes to write uint8_t* buffer = 0) for inclusion in the header file, after a little editing, would be fine. Getting this back: i2cstatus_t writeRegisters( uint8_t start_register, uint8_t bytes_to_write, uint8_t* buffer); or this: i2cstatus_t writeRegisters(uint8_t start_register, uint8_t bytes_to_write, uint8_t* buffer); would be even better.

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  • Positioning objects in views during re-orientation in iPad

    - by Arni
    iPad Gurus: Apple wants us to support all orientations. I take that to mean that a particular layout should either rotate so that all objects are positioned relatively the same OR, if that doesn't look good, then they ought to be repositioned, OR two views ought to be designed and built. If I rely on the built-in rotation mechanism, the objects either get resized or they straddle the edge of the page in one orientation or the other, or they disappear from view altogether. I can't seem to find the right settings to get the objects to align clearly so they are seen in each orientation. Repositioning leads to a lot of if statements in the View Controller. So I don't think Apple had that in mind. I tried replacing views and even view controllers in "willRotateToInterfaceOrientation" method, but that either causes crashes or the portrait views end up in landscape unexpectedly and vv. Moreover, two view controllers means double the coding for the same view. There must be proper way to handle orientation changes, but I have searched the internet and documentation and sample code in vain for something that works. How is this done properly? Thanks!

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