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• What is "elegant" code?

  - by Breton

  I see a lot of lip service and talk about the most "elegant" way to do this or that. I think if you spend enough time programming you begin to obtain a sort of intuitive feel for what it is we call "elegance". But I'm curious. Even if we can look at a bit of code, and say instinctively "That's elegant", or "That's messy", I wonder if any of us really understands what that means. Is there a precise definition for this "elegance" we keep referring to? If there is, what is it? Now, what I mean by a precise definition, is a series of statements which can be used to derive questions about a peice of code, or a program as a whole, and determine objectively, or as objectively as possible, whether that code is "elegant" or not. May I assert, that perhaps no such definition exists, and it's all just personal preference. In this case, I ask you a slightly different question: Is there a better word for "elegance", or a better set of attributes to use for judging code quality that is perhaps more objective than merely appealing to individual intuition and taste? Perhaps code quality is a matter of taste, and the answer to both of my questions is "no". But I can't help but feel that we could be doing better than just expressing wishy washy feelings about our code quality. For example, user interface design is something that to a broad range of people looks for all the world like a field of study that oughtta be 100% subjective matter of taste. But this is shockingly and brutally not the case, and there are in fact many objective measures that can be applied to a user interface to determine its quality. A series of tests could be written to give a definitive and repeatable score to user interface quality. (See GOMS, for instance). Now, okay. is Elegance simply "code quality" or is it something more? Is it something that can be measured? Or is it a matter of taste? Does our profession have room for taste? Maybe I'm asking the wrong questions altogether. Help me out here. Bonus Round If there is such a thing as elegance in code, and that concept is useful, do you think that justifies classifying the field of programming as an "Art" capital A, or merely a "craft". Or is it just an engineering field populated by a bunch of wishful thinking humans? Consider this question in the light of your thoughts about the elegance question. Please note that there is a distinction between code which is considered "art" in itself, and code that was written merely in the service of creating an artful program. When I ask this question, I ask if the code itself justifies calling programming an art. Bounty Note I liked the answers to this question so much, I think I'd like to make a photographic essay book from it. Released as a free PDF, and published on some kind of on demand printing service of course, such as "zazz" or "tiggle" or "printley" or something . I'd like some more answers, please!

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• Vista/7: How to get glass color?

  - by Ian Boyd

  How do you use DwmGetColorizationColor? The documentation says it returns two values: a 32-bit 0xAARRGGBB containing the color used for glass composition a boolean parameter that is true "if the color is an opaque blend" (whatever that means) Here's a color that i like, a nice puke green: You can notice the color is greeny, and the translucent title bar (against a white background) shows the snot color very clearly: i try to get the color from Windows: DwmGetColorizationColor(dwCcolorization, bIsOpaqueBlend); And i get dwColorization: 0x0D0A0F04 bIsOpaqueBlend: false According to the documentation this value is of the format AARRGGBB, and so contains: AA: 0x0D (13) RR: 0x0A (10) GG: 0x0F (15) BB: 0x04 (4) This supposedly means that the color is (10, 15, 4), with an opacity of ~5.1%. But if you actually look at this RGB value, it's nowhere near my desired snot green. Here is (10, 15, 4) with zero opacity (the original color), and (10,15,4) with 5% opacity against a white/checkerboard background: So the question is: How to get glass color in Windows Vista/7? i tried using DwmGetColorizationColor, but that doesn't work very well. A person with same problem, but a nicer shiny picture to attract you squirrels: So, it boils down to – DwmGetColorizationColor is completely unusable for applications attempting to apply the current color onto an opaque surface. i love this guy's screenshots much better than mine. Using his screenshots as a template, i made up a few more sparklies: For the last two screenshots, the alpha blended chip is a true partially transparent PNG, blending to your browser's background. Cool! (i'm such a geek) Edit 2: Had to arrange them in rainbow color. (i'm such a geek) Edit 3: Well now i of course have to add Yellow. Undocumented/Unsupported/Fragile Workarounds There is an undocumented export from DwmApi.dll at entry point 137, which we'll call DwmGetColorizationParameters: HRESULT GetColorizationParameters_Undocumented(out DWMCOLORIZATIONPARAMS params); struct DWMCOLORIZATIONPARAMS { public UInt32 ColorizationColor; public UInt32 ColorizationAfterglow; public UInt32 ColorizationColorBalance; public UInt32 ColorizationAfterglowBalance; public UInt32 ColorizationBlurBalance; public UInt32 ColorizationGlassReflectionIntensity; public UInt32 ColorizationOpaqueBlend; } We're interested in the first parameter: ColorizationColor. We can also read the value out of the registry: HKEY_CURRENT_USER\Software\Microsoft\Windows\DWM ColorizationColor: REG_DWORD = 0x6614A600 So you pick your poison of creating appcompat issues. You can rely on an undocumented API (which is bad, bad, bad, and can go away at any time) use an undocumented registry key (which is also bad, and can go away at any time) See also Is there a list of valid parameter combinations for GetThemeColor / Visual Styles API How does Windows change Aero Glass color? DWM - Colorization Color Handling Using DWMGetColorizationColor Retrieving Aero Glass base color for opaque surface rendering i've been wanting to ask this question for over a year now. i always knew that it's impossible to answer, and that the only way to get anyone to actually pay attention is to have colorful screenshots; developers are attracted to shiny things. But on the downside it means i had to put all kinds of work into making the lures.

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• C# Windows Service XML

  - by Goober

  Scenario I have a windows service written in C# that performs some processing based on parsing an XML file and use that data to carry out various tasks. The service also does various bits of logging - which uses settings from an APP.Config file. The Problem When the service is compiled, installed and run, the XML file seems to disappear. I'm getting the impression that it is just ignored or something like that. So far I've tried using TWO App.Config files, one named App.Config that contains settings for the service, and the other called MyService.exe.config that contains all of the data that was used in the XML file (the idea being that I can parse the XML from a config file that actually gets compiled and appears in my installation directory. However When I do this, all that happens is that ONE config file appears (with the name MyService.exe.config), but it contains the contents of the App.Config file and not the XML data that I want to parse. What I need All I want is to have a config file for my settings, and an XML file for my data. Question Is this possible? I know the application works as it was originally built as a console application that ran fine. Other The application has to be designed this way (as in, I need my data stored as XML, and my settings stored in a config file). Thoughts If I could somehow combine the contents of the two files into ONE config file, that would be one way of solving the problem. However, I have tried this and of course I get a "Type Initialisation Exception", as the config file cannot interprate the XML data (probably because the tags are custom and do not form any part of the config schema - or something like that). Ideas Please could someone explain to me if it is possible for me to have an XML file AND a config file that will actually be compiled and stored in my installation directory for the service when it is run? CODE Custom XML/Data Config File <?xml version="1.0" encoding="utf-8" ?> <configuration> <servers> <SV066930> <add name="Name" value = "SV066930" /> <processes> <SimonTest1> <add name="ProcessName" value="notepad.exe" /> <add name="CommandLine" value="C:\\WINDOWS\\system32\\notepad.exe C:\\WINDOWS\\Profiles\\TA2TOF1\\Desktop\\SimonTest1.txt" /> </SimonTest1> </processes> </SV066930> </servers> </configuration> APP.Config Settings File <?xml version="1.0" encoding="utf-8" ?> <configuration> <configSections> <section name="dataConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.DatabaseSettings, Microsoft.Practices.EnterpriseLibrary.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=xxxxxxxxxxx" /> </configSections> <connectionStrings> <add name="DB" connectionString="Data Source=etc......" /> </connectionStrings> </configuration> Help greatly appreciated.

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• Grafting LINQ onto C# 2 library

  - by P Daddy

  I'm writing a data access layer. It will have C# 2 and C# 3 clients, so I'm compiling against the 2.0 framework. Although encouraging the use of stored procedures, I'm still trying to provide a fairly complete ability to perform ad-hoc queries. I have this working fairly well, already. For the convenience of C# 3 clients, I'm trying to provide as much compatibility with LINQ query syntax as I can. Jon Skeet noticed that LINQ query expressions are duck typed, so I don't have to have an IQueryable and IQueryProvider (or IEnumerable<T>) to use them. I just have to provide methods with the correct signatures. So I got Select, Where, OrderBy, OrderByDescending, ThenBy, and ThenByDescending working. Where I need help are with Join and GroupJoin. I've got them working, but only for one join. A brief compilable example of what I have is this: // .NET 2.0 doesn't define the Func<...> delegates, so let's define some workalikes delegate TResult FakeFunc<T, TResult>(T arg); delegate TResult FakeFunc<T1, T2, TResult>(T1 arg1, T2 arg2); abstract class Projection{ public static Condition operator==(Projection a, Projection b){ return new EqualsCondition(a, b); } public static Condition operator!=(Projection a, Projection b){ throw new NotImplementedException(); } } class ColumnProjection : Projection{ readonly Table table; readonly string columnName; public ColumnProjection(Table table, string columnName){ this.table = table; this.columnName = columnName; } } abstract class Condition{} class EqualsCondition : Condition{ readonly Projection a; readonly Projection b; public EqualsCondition(Projection a, Projection b){ this.a = a; this.b = b; } } class TableView{ readonly Table table; readonly Projection[] projections; public TableView(Table table, Projection[] projections){ this.table = table; this.projections = projections; } } class Table{ public Projection this[string columnName]{ get{return new ColumnProjection(this, columnName);} } public TableView Select(params Projection[] projections){ return new TableView(this, projections); } public TableView Select(FakeFunc<Table, Projection[]> projections){ return new TableView(this, projections(this)); } public Table Join(Table other, Condition condition){ return new JoinedTable(this, other, condition); } public TableView Join(Table inner, FakeFunc<Table, Projection> outerKeySelector, FakeFunc<Table, Projection> innerKeySelector, FakeFunc<Table, Table, Projection[]> resultSelector){ Table join = new JoinedTable(this, inner, new EqualsCondition(outerKeySelector(this), innerKeySelector(inner))); return join.Select(resultSelector(this, inner)); } } class JoinedTable : Table{ readonly Table left; readonly Table right; readonly Condition condition; public JoinedTable(Table left, Table right, Condition condition){ this.left = left; this.right = right; this.condition = condition; } } This allows me to use a fairly decent syntax in C# 2: Table table1 = new Table(); Table table2 = new Table(); TableView result = table1 .Join(table2, table1["ID"] == table2["ID"]) .Select(table1["ID"], table2["Description"]); But an even nicer syntax in C# 3: TableView result = from t1 in table1 join t2 in table2 on t1["ID"] equals t2["ID"] select new[]{t1["ID"], t2["Description"]}; This works well and gives me identical results to the first case. The problem is if I want to join in a third table. TableView result = from t1 in table1 join t2 in table2 on t1["ID"] equals t2["ID"] join t3 in table3 on t1["ID"] equals t3["ID"] select new[]{t1["ID"], t2["Description"], t3["Foo"]}; Now I get an error (Cannot implicitly convert type 'AnonymousType#1' to 'Projection[]'), presumably because the second join is trying to join the third table to an anonymous type containing the first two tables. This anonymous type, of course, doesn't have a Join method. Any hints on how I can do this?

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• developing maven plugin, how to exclude bitkeeper files

  - by Denali

  Hi There, I am trying to write my first maven plugin. I'd like to exclude all the java files related to the source repository I'm using, which is BitKeeper. These files live in directories called SCCS. I can't for the life of me figure out how to do this. When I add the maven-compile-plugin with excludes data, it works (the bk files are excluded) if I specify mvn compiler:compile. But this is not binding to the compile phase. So that when I run mvn compile, it blows up trying to compile a source control specific java file. Any help or pointers appreciated. Another thing to note: Everything works perfectly if I change the packaging from "maven-plugin" to "jar", which of course, I can't do permanently since this is a maven plugin I am trying to write. I'm sorry if this is answered elsewhere. I've looked around for several hours here and through the maven docs, but everything on this topic seems to be related to writing code which will be packaged in jars, not maven plugins. Here's my pom.xml: <project> <modelVersion>4.0.0</modelVersion> <groupId>com.mycomp.mygroup</groupId> <artifactId>special-persistence-plugin</artifactId> <packaging>maven-plugin</packaging> <version>1.0-SNAPSHOT</version> <name>Special Persistence Plugin</name> <dependencies> <dependency> <groupId>org.apache.maven</groupId> <artifactId>maven-plugin-api</artifactId> <version>2.0</version> </dependency> </dependencies> <build> <plugins> <plugin> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.6</source> <target>1.6</target> <encoding>UTF-8</encoding> <excludes> <exclude>**/SCCS/**/*.java</exclude> </excludes> <phase>compile</phase> <goals> <goal>compiler:compile</goal> </goals> </configuration> </plugin> </plugins> </build> </project> Thank you to anyone with ideas about this, -Denali

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• Select number of rows for each group where two column values makes one group

  - by Fábio Antunes

  I have a two select statements joined by UNION ALL. In the first statement a where clause gathers only rows that have been shown previously to the user. The second statement gathers all rows that haven't been shown to the user, therefore I end up with the viewed results first and non-viewed results after. Of course this could simply be achieved with the same select statement using a simple ORDER BY, however the reason for two separate selects is simple after you realize what I hope to accomplish. Consider the following structure and data. +----+------+-----+--------+------+ | id | from | to | viewed | data | +----+------+-----+--------+------+ | 1 | 1 | 10 | true | .... | | 2 | 10 | 1 | true | .... | | 3 | 1 | 10 | true | .... | | 4 | 6 | 8 | true | .... | | 5 | 1 | 10 | true | .... | | 6 | 10 | 1 | true | .... | | 7 | 8 | 6 | true | .... | | 8 | 10 | 1 | true | .... | | 9 | 6 | 8 | true | .... | | 10 | 2 | 3 | true | .... | | 11 | 1 | 10 | true | .... | | 12 | 8 | 6 | true | .... | | 13 | 10 | 1 | false | .... | | 14 | 1 | 10 | false | .... | | 15 | 6 | 8 | false | .... | | 16 | 10 | 1 | false | .... | | 17 | 8 | 6 | false | .... | | 18 | 3 | 2 | false | .... | +----+------+-----+--------+------+ Basically I wish all non viewed rows to be selected by the statement, that is accomplished by checking weather the viewed column is true or false, pretty simple and straightforward, nothing to worry here. However when it comes to the rows already viewed, meaning the column viewed is TRUE, for those records I only want 3 rows to be returned for each group. The appropriate result in this instance should be the 3 most recent rows of each group. +----+------+-----+--------+------+ | id | from | to | viewed | data | +----+------+-----+--------+------+ | 6 | 10 | 1 | true | .... | | 7 | 8 | 6 | true | .... | | 8 | 10 | 1 | true | .... | | 9 | 6 | 8 | true | .... | | 10 | 2 | 3 | true | .... | | 11 | 1 | 10 | true | .... | | 12 | 8 | 6 | true | .... | +----+------+-----+--------+------+ As you see from the ideal result set we have three groups. Therefore the desired query for the viewed results should show a maximum of 3 rows for each grouping it finds. In this case these groupings were 10 with 1 and 8 with 6, both which had three rows to be shown, while the other group 2 with 3 only had one row to be shown. Please note that where from = x and to = y, makes the same grouping as if it was from = y and to = x. Therefore considering the first grouping (10 with 1), from = 10 and to = 1 is the same group if it was from = 1 and to = 10. However there are plenty of groups in the whole table that I only wish the 3 most recent of each to be returned in the select statement, and thats my problem, I not sure how that can be accomplished in the most efficient way possible considering the table will have hundreds if not thousands of records at some point. Thanks for your help. Note: The columns id, from, to and viewed are indexed, that should help with performance. PS: I'm unsure on how to name this question exactly, if you have a better idea, be my guest and edit the title.

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• Two UIViews, one UIViewController (in one UINavigationController)

  - by jdandrea

  Given an iPhone app with a UITableViewController pushed onto a UINavigationController, I would like to add a right bar button item to toggle between the table view and an "alternate" view of the same data. Let's also say that this other view uses the same data but is not a UITableView. Now, I know variations on this question already exist on Stack Overflow. However, in this case, that alternate view would not be pushed onto the UINavigationController. It would be visually akin to flipping the current UIViewController's table view over and revealing the other view, then being able to flip back. In other words, it's intended to take up a single spot in the UINavigationController hierarchy. Moreover, whatever selection you ultimately make from within either view will push a common UIViewController onto the UINavigationController stack. Still more info: We don't want to use a separate UINavigationController just to handle this pair of views, and we don't want to split these apart via a UITabBarController either. Visually and contextually, the UX is meant to show two sides of the same coin. It's just that those two sides happen to involve their own View Controllers in normal practice. Now … it turns out I have already gone and quickly set this up to see how it might work! However, upon stepping back to examine it, I get the distinct impression that I went about it in a rather non-MVC way, which of course concerns me a bit. Here's what I did at a high level. Right now, I have a UIViewController (not a UITableViewController) that handles all commonalities between the two views, such as fetching the raw data. I also have two NIBs, one for each view, and two UIView objects to go along with them. (One of them is a UITableView, which is a kind of UIView.) I switch between the views using animation (easy enough). Also, in an effort to keep things encapsulated, the now-split-apart UITableView (not the UIViewController!) acts as its own delegate and data source, fetching data from the VC. The VC is set up as a weak, non-retained object in the table view. In parallel, the alternate view gets at the raw data from the VC in the exact same way. So, there are a few things that smell funny here. The weak linking from child to parent, while polite, seems like it might be wrong. Making a UITableView the table's data source and delegate also seems odd to me, thinking that a view controller is where you want to put that per Apple's MVC diagrams. As it stands now, it would appear as if the view knows about the model, which isn't good. Loading up both views in advance also seems odd, because lazy loading is no longer in effect. Losing the benefits of a UITableViewController (like auto-scrolling to cells with text fields) is also a bit frustrating, and I'd rather not reinvent the wheel to work around that as well. Given all of the above, and given we want that "flip effect" in the context of a single spot on a single UINavigationController, and given that both views are two sides of the same coin, is there a better, more obvious way to design this that I'm just happening to miss completely? Clues appreciated!

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• JPA IndirectSet changes not reflected in Spring frontend

  - by Jon

  I'm having an issue with Spring JPA and IndirectSets. I have two entities, Parent and Child, defined below. I have a Spring form in which I'm trying to create a new Child and link it to an existing Parent, then have everything reflected in the database and in the web interface. What's happening is that it gets put into the database, but the UI doesn't seem to agree. The two entities that are linked to each other in a OneToMany relationship like so: @Entity @Table(name = "parent", catalog = "myschema", uniqueConstraints = @UniqueConstraint(columnNames = "ChildLinkID")) public class Parent { private Integer id; private String childLinkID; private Set<Child> children = new HashSet<Child>(0); @Id @GeneratedValue(strategy = IDENTITY) @Column(name = "id", unique = true, nullable = false) public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } @Column(name = "ChildLinkID", unique = true, nullable = false, length = 6) public String getChildLinkID() { return this.childLinkID; } public void setChildLinkID(String childLinkID) { this.childLinkID = childLinkID; } @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "parent") public Set<Child> getChildren() { return this.children; } public void setChildren(Set<Child> children) { this.children = children; } } @Entity @Table(name = "child", catalog = "myschema") public class Child extends private Integer id; private Parent parent; @Id @GeneratedValue(strategy = IDENTITY) @Column(name = "id", unique = true, nullable = false) public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "ChildLinkID", referencedColumnName = "ChildLinkID", nullable = false) public Parent getParent() { return this.parent; } public void setParent(Parent parent) { this.parent = parent; } } And of course, assorted simple properties on each of them. Now, the problem is that when I edit those simple properties from my Spring interface, everything works beautifully. I can persist new entities of these types and they'll appear when using the JPATemplate to do a find on, say, all Parents (getJpaTemplate().find("select p from Parent p")) or on individual entities by ID or another property. The problem I'm running into is that now, I'm trying to create a new Child linked to an existing Parent through a link from the Parent's page. Here's the important bits of the Controller (note that I've placed the JPA foo in the controller here to make it clearer; the actual JpaDaoSupport is actually in another class, appropriately tiered): protected Object formBackingObject(HttpServletRequest request) throws Exception { String parentArg = request.getParameter("parent"); int parentId = Integer.parseInt(parentArg); Parent parent = getJpaTemplate().find(Parent.class, parentId); Child child = new Child(); child.setParent(parent); NewChildCommand command = new NewChildCommand(); command.setChild(child); return command; } protected ModelAndView onSubmit(Object cmd) throws Exception { NewChildCommand command = (NewChildCommand)cmd; Child child = command.getChild(); child.getParent().getChildren().add(child); getJpaTemplate().merge(child); return new ModelAndView(new RedirectView(getSuccessView())); } Like I said, I can run through the form and fill in the new values for the Child -- the Parent's details aren't even displayed. When it gets back to the controller, it goes through and saves it to the underlying database, but the interface never reflects it. Once I restart the app, it's all there and populated appropriately. What can I do to clear this up? I've tried to call extra merges, tried refreshes (which gave a transaction exception), everything short of just writing my own database access code. I've made sure that every class has an appropriate equals() and hashCode(), have full JPA debugging on to see that it's making appropriate SQL calls (it doesn't seem to make any new calls to the Child table) and stepped through in the debugger (it's all in IndirectSets, as expected, and between saving and displaying the Parent the object takes on a new memory address). What's my next step?

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• How do you stop scripters from slamming your website hundreds of times a second?

  - by davebug

  [update] I've accepted an answer, as lc deserves the bounty due to the well thought-out answer, but sadly, I believe we're stuck with our original worst case scenario: CAPTCHA everyone on purchase attempts of the crap. Short explanation: caching / web farms make it impossible for us to actually track hits, and any workaround (sending a non-cached web-beacon, writing to a unified table, etc.) slows the site down worse than the bots would. There is likely some pricey bit of hardware from Cisco or the like that can help at a high level, but it's hard to justify the cost if CAPTCHAing everyone is an alternative. I'll attempt to do a more full explanation in here later, as well as cleaning this up for future searchers (though others are welcome to try, as it's community wiki). I've added bounty to this question and attempted to explain why the current answers don't fit our needs. First, though, thanks to all of you who have thought about this, it's amazing to have this collective intelligence to help work through seemingly impossible problems. I'll be a little more clear than I was before: This is about the bag o' crap sales on woot.com. I'm the president of Woot Workshop, the subsidiary of Woot that does the design, writes the product descriptions, podcasts, blog posts, and moderates the forums. I work in the css/html world and am only barely familiar with the rest of the developer world. I work closely with the developers and have talked through all of the answers here (and many other ideas we've had). Usability of the site is a massive part of my job, and making the site exciting and fun is most of the rest of it. That's where the three goals below derive. CAPTCHA harms usability, and bots steal the fun and excitement out of our crap sales. To set up the scenario a little more, bots are slamming our front page tens of times a second screenscraping (and/or scanning our rss) for the Random Crap sale. The moment they see that, it triggers a second stage of the program that logs in, clicks I want One, fills out the form, and buys the crap. In current (2/6/2009) order of votes: lc: On stackoverflow and other sites that use this method, they're almost always dealing with authenticated (logged in) users, because the task being attempted requires that. On Woot, anonymous (non-logged) users can view our home page. In other words, the slamming bots can be non-authenticated (and essentially non-trackable except by IP address). So we're back to scanning for IPs, which a) is fairly useless in this age of cloud networking and spambot zombies and b) catches too many innocents given the number of businesses that come from one IP address (not to mention the issues with non-static IP ISPs and potential performance hits to trying to track this). Oh, and having people call us would be the worst possible scenario. Can we have them call you? BradC Ned Batchelder's methods look pretty cool, but they're pretty firmly designed to defeat bots built for a network of sites. Our problem is bots are built specifically to defeat our site. Some of these methods could likely work for a short time until the scripters evolved their bots to ignore the honeypot, screenscrape for nearby label names instead of form ids, and use a javascript-capable browser control. lc again "Unless, of course, the hype is part of you

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• What's the right way to do mutable data structures (e.g., skip lists, splay trees) in F#?

  - by dan

  What's a good way to implement mutable data structures in F#? The reason I’m asking is because I want to go back and implement the data structures I learned about in the algorithms class I took this semester (skip lists, splay trees, fusion trees, y-fast tries, van Emde Boas trees, etc.), which was a pure theory course with no coding whatsoever, and I figure I might as well try to learn F# while I’m doing it. I know that I “should” use finger trees to get splay tree functionality in a functional language, and that I should do something with laziness to get skip-list functionality, etc. , but I want to get the basics nailed down before I try playing with purely functional implementations. There are lots of examples of how to do functional data structures in F#, but there isn’t much on how to do mutable data structures, so I started by fixing up the doubly linked list here into something that allows inserts and deletes anywhere. My plan is to turn this into a skip list, and then use a similar structure (discriminated union of a record) for the tree structures I want to implement. Before I start on something more substantial, is there a better way to do mutable structures like this in F#? Should I just use records and not bother with the discriminated union? Should I use a class instead? Is this question "not even wrong"? Should I be doing the mutable structures in C#, and not dip into F# until I want to compare them to their purely functional counterparts? And, if a DU of records is what I want, could I have written the code below better or more idiomatically? It seems like there's a lot of redundancy here, but I'm not sure how to get rid of it. module DoublyLinkedList = type 'a ll = | None | Node of 'a ll_node and 'a ll_node = { mutable Prev: 'a ll; Element : 'a ; mutable Next: 'a ll; } let insert x l = match l with | None -> Node({ Prev=None; Element=x; Next=None }) | Node(node) -> match node.Prev with | None -> let new_node = { Prev=None; Element=x; Next=Node(node)} node.Prev <- Node(new_node) Node(new_node) | Node(prev_node) -> let new_node = { Prev=node.Prev; Element=x; Next=Node(node)} node.Prev <- Node(new_node) prev_node.Next <- Node(new_node) Node(prev_node) let rec nth n l = match n, l with | _,None -> None | _,Node(node) when n > 0 -> nth (n-1) node.Next | _,Node(node) when n < 0 -> nth (n+1) node.Prev | _,Node(node) -> Node(node) //hopefully only when n = 0 :-) let rec printLinkedList head = match head with | None -> () | Node(x) -> let prev = match x.Prev with | None -> "-" | Node(y) -> y.Element.ToString() let cur = x.Element.ToString() let next = match x.Next with | None -> "-" | Node(y) -> y.Element.ToString() printfn "%s, <- %s -> %s" prev cur next printLinkedList x.Next

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• Slide div inside another div effect

  - by mariki

  I am trying to create sliding images effect: Online demolink text. The problem is when you click rapidly and randomly on the buttons and not wait for animation to finish causing unpredicted results and even stopping the functionality to work. (and once it stopped in the middle of 2 images...) How Can I make it work without bugs? I know that there are some other tools for that sliding like jquery and other approaches like changing the position attribute and not the scrollLeft attribute. But I want to do it as it is, with scrollLeft, if it possible of course. The Code: <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <title>Untitled Document</title> <style type="text/css"> body { padding:0px; margin:0px; } #imageContainer { width: 500px; position: relative; } #div { overflow: hidden; white-space: nowrap; } #div img { cursor: pointer; vertical-align: bottom; width: 500px; padding:0px; margin:0px; display:inline; } </style> <script type="text/javascript"> var scrollIntervalID; var currentIndex=0; function Scroll(ind){ var dir = ind ==currentIndex?0:ind<currentIndex?-1:1; var steps = Math.abs(ind-currentIndex); scrollIntervalID = setInterval(function(){ var i=(steps*10)-1; return function(){ if (i <= 0) clearInterval(scrollIntervalID); var elm = document.getElementById("div"); elm.scrollLeft +=dir * 50; i--; document.getElementById("span").innerHTML=elm.scrollLeft; } }(), 15); currentIndex=ind; } </script> </head> <body> <div id="imageContainer"> <div id="div"> <img id="image1" src="Images/pic1.jpg" width="500px"/><img id="image2" src="Images/pic2.jpg" width="500px"/><img id="image3" src="Images/pic3.jpg" width="500px"/><img id="image4" src="Images/pic4.jpg" width="500px"/> </div> </div> <div> <input type="button" value="1" onclick="Scroll(0);"/> <input type="button" value="2" onclick="Scroll(1);"/> <input type="button" value="3" onclick="Scroll(2);"/> <input type="button" value="4" onclick="Scroll(3);"/> </div> <span id="span"></span> </body> </html>

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• Javascript Closures - What are the negatives?

  - by vol7ron

  Question: There seem to be many benefits to Closures, but what are the negatives (memory leakage? obfuscation problems? bandwidth increasage?)? Additionally, is my understanding of Closures correct? Finally, once closures are created, can they be destroyed? I've been reading a little bit about Javascript Closures. I hope someone a little more knowledgeable will guide my assertions, correcting me where wrong. Benefits of Closures: Encapsulate the variables to a local scope, by using an internal function. The anonymity of the function is insignificant. What I've found helpful is to do some basic testing, regarding local/global scope: <script type="text/javascript"> var global_text = ""; var global_count = 0; var global_num1 = 10; var global_num2 = 20; var global_num3 = 30; function outerFunc() { var local_count = local_count || 0; alert("global_num1: " + global_num1); // global_num1: undefined var global_num1 = global_num1 || 0; alert("global_num1: " + global_num1); // global_num1: 0 alert("global_num2: " + global_num2); // global_num2: 20 global_num2 = global_num2 || 0; // (notice) no definition with 'var' alert("global_num2: " + global_num2); // global_num2: 20 global_num2 = 0; alert("local_count: " + local_count); // local_count: 0 function output() { global_num3++; alert("local_count: " + local_count + "\n" + "global_count: " + global_count + "\n" + "global_text: " + global_text ); local_count++; } local_count++; global_count++; return output; } var myFunc = outerFunc(); myFunc(); /* Outputs: ********************** * local_count: 1 * global_count: 1 * global_text: **********************/ global_text = "global"; myFunc(); /* Outputs: ********************** * local_count: 2 * global_count: 1 * global_text: global **********************/ var local_count = 100; myFunc(); /* Outputs: ********************** * local_count: 3 * global_count: 1 * global_text: global **********************/ alert("global_num1: " + global_num1); // global_num1: 10 alert("global_num2: " + global_num2); // global_num2: 0 alert("global_num3: " + global_num3); // global_num3: 33 </script> Interesting things I took out of it: The alerts in outerFunc are only called once, which is when the outerFunc call is assigned to myFunc (myFunc = outerFunc()). This assignment seems to keep the outerFunc open, in what I would like to call a persistent state. Everytime myFunc is called, the return is executed. In this case, the return is the internal function. Something really interesting is the localization that occurs when defining local variables. Notice the difference in the first alert between global_num1 and global_num2, even before the variable is trying to be created, global_num1 is considered undefined because the 'var' was used to signify a local variable to that function. -- This has been talked about before, in the order of operation for the Javascript engine, it's just nice to see this put to work. Globals can still be used, but local variables will override them. Notice before the third myFunc call, a global variable called local_count is created, but it as no effect on the internal function, which has a variable that goes by the same name. Conversely, each function call has the ability to modify global variables, as noticed by global_var3. Post Thoughts: Even though the code is straightforward, it is cluttered by alerts for you guys, so you can plug and play. I know there are other examples of closures, many of which use anonymous functions in combination with looping structures, but I think this is good for a 101-starter course to see the effects. The one thing I'm concerned with is the negative impact closures will have on memory. Because it keeps the function environment open, it is also keeping those variables stored in memory, which may/may not have performance implications, especially regarding DOM traversals and garbage collection. I'm also not sure what kind of role this will play in terms of memory leakage and I'm not sure if the closure can be removed from memory by a simple "delete myFunc;." Hope this helps someone, vol7ron

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• Is this a right way to use NHibernate?

  - by Venemo

  I spent the rest of the evening reading StackOverflow questions and also some blog entries and links about the subject. All of them turned out to be very helpful, but I still feel that they don't really answer my question. So, I'm developing a simple web application. I'd like to create a reusable data access layer which I can later reuse in other solutions. 99% of these will be web applications. This seems to be a good excuse for me to learn NHibernate and some of the patterns around it. My goals are the following: I don't want the business logic layer to know ANYTHING about the inner workings of the database, nor NHibernate itself. I want the business logic layer to have the least possible number of assumptions about the data access layer. I want the data access layer as simplistic and easy-to-use as possible. This is going to be a simple project, so I don't want to overcomplicate anything. I want the data access layer to be as non-intrusive as possible. Will all this in mind, I decided to use the popular repository pattern. I read about this subject on this site and on various dev blogs, and I heard some stuff about the unit of work pattern. I also looked around and checked out various implementations. (Including FubuMVC contrib, and SharpArchitecture, and stuff on some blogs.) I found out that most of these operate with the same principle: They create a "unit of work" which is instantiated when a repository is instantiated, they start a transaction, do stuff, and commit, and then start all over again. So, only one ISession per Repository and that's it. Then the client code needs to instantiate a repository, do stuff with it, and then dispose. This usage pattern doesn't meet my need of being as simplistic as possible, so I began thinking about something else. I found out that NHibernate already has something which makes custom "unit of work" implementations unnecessary, and that is the CurrentSessionContext class. If I configure the session context correctly, and do the clean up when necessary, I'm good to go. So, I came up with this: I have a static class called NHibernateHelper. Firstly, it has a static property called CurrentSessionFactory, which upon first call, instantiates a session factory and stores it in a static field. (One ISessionFactory per one AppDomain is good enough.) Then, more importantly, it has a CurrentSession static property, which checks if there is an ISession bound to the current session context, and if not, creates one, and binds it, and it returns with the ISession bound to the current session context. Because it will be used mostly with WebSessionContext (so, one ISession per HttpRequest, although for the unit tests, I configured ThreadStaticSessionContext), it should work seamlessly. And after creating and binding an ISession, it hooks an event handler to the HttpContext.Current.ApplicationInstance.EndRequest event, which takes care of cleaning up the ISession after the request ends. (Of course, it only does this if it is really running in a web environment.) So, with all this set up, the NHibernateHelper will always be able to return a valid ISession, so there is no need to instantiate a Repository instance for the "unit of work" to operate properly. Instead, the Repository is a static class which operates with the ISession from the NHibernateHelper.CurrentSession property, and exposes some functionality through that. I'm curious, what do you think about this? Is it a valid way of thinking, or am I completely off track here?

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• HttpWebRequest response produces HTTP 422. Why?

  - by Simon

  Hi there. I'm trying to programmatically send a POST-request to a web-server in order to login an then perform other requests that require a login. This is my code: Encoding.UTF8.GetBytes( String.Format( "login={0}&password={1}&authenticity_token={2}", username, password, token)); //Create HTTP-request for login HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("http://www.xxx.xx/xx/xx"); request.Method = "POST"; request.ContentType = "application/x-www-form-urlencoded"; request.ContentLength = data.Length; request.CookieContainer = new CookieContainer(); request.Accept = "application/xml,application/xhtml+xml,text/html; +"q=0.9,text/plain ;q=0.8,image/png,*/*;q=0.5"; request.Referer = "http://www.garzantilinguistica.it/it/session"; request.Headers.Add("Accept-Language", "de-DE"); request.Headers.Add("Origin", "http://www.xxx.xx"); request.UserAgent = "C#"; request.Headers.Add("Accept-Encoding", "gzip, deflate"); After sending the request //Send post request var requestStream = request.GetRequestStream(); requestStream.Write(data, 0, data.Length); requestStream.Flush(); requestStream.Close(); ... I want to get the servers response: //Get Response StreamReader responseStreamReader = new StreamReader( request.GetResponse().GetResponseStream()); //WebException: HTTP 422! string content = responseStreamReader.ReadToEnd(); This piece of code fires the WebException, that tells me the server responded with HTTP 422 (unprocessable entity due to semantic errors) Then I compared (using a TCP/IP sniffers) the requests of my program and the browser (which of course produces a valid POST-request and gets the right response). (1) My program's request: POST /it/session HTTP/1.1 Content-Type: application/x-www-form-urlencoded Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain; q=0.8,image/png,*/*;q=0.5 Referer: http://www.garzantilinguistica.it/it/session Accept-Language: de-DE Origin: http://www.garzantilinguistica.it User-Agent: C# Accept-Encoding: gzip, deflate Host: www.garzantilinguistica.it Content-Length: 111 Expect: 100-continue Connection: Keep-Alive HTTP/1.1 100 Continue [email protected]&password=machivui&authenticity_token=4vLgtwP3nFNg4NeuG4MbUnU7sy4z91Wi8WJXH0POFmg= HTTP/1.1 422 Unprocessable Entity (2) The browser's request: POST /it/session HTTP/1.1 Host: www.garzantilinguistica.it Referer: http://www.garzantilinguistica.it/it/session Accept: application/xml,application/xhtml+xml,text/html;q=0.9, text/plain;q=0.8,image/png,*/*;q=0.5 Accept-Language: de-DE Origin: http://www.garzantilinguistica.it User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de-DE) AppleWebKit/531.22.7 (KHTML, like Gecko) Version/4.0.5 Safari/531.22.7 Accept-Encoding: gzip, deflate Content-Type: application/x-www-form-urlencoded Cookie: __utma=244184339.652523587.1275208707.1275208707.1275211298.2; __utmb=244184339.20.10.1275211298; __utmc=244184339; __utmz=244184339.1275208707.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); _garzanti2009_session=BAh7CDoPc2Vzc2lvbl9pZCIlZDg4MWZjNjg2YTRhZWE0NDQ0ZTJmMTU2YWY4ZTQ1NGU6EF9jc3JmX3Rva2VuIjFqRWdLdll3dTYwOTVVTEpNZkt6dG9jUCtaZ0o4V0FnV2V5ZnpuREx6QUlZPSIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6Rmxhc2g6OkZsYXNoSGFzaHsGOgplcnJvciIVbG9naW4gbm9uIHZhbGlkbwY6CkB1c2VkewY7CFQ%3D--4200fa769898dd156faa49e457baf660cf068d08 Content-Length: 144 Connection: keep-alive authenticity_token=jEgKvYwu6095ULJMfKztocP%2BZgJ8WAgWeyfznDLzAIY%3D&login=thespider14%40hotmail.com&password=machivui&remember_me=1&commit=Entra HTTP/1.1 302 Found Can someone help to understand which part of the request I am missing or what the main difference between the browser's and my request is? Why am I getting that 422?

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• C++ MySQL++ Delete query statement brain killer question

  - by shauny

  Hello all, I'm relatively new to the MySQL++ connector in C++, and have an really annoying issue with it already! I've managed to get stored procedures working, however i'm having issues with the delete statements. I've looked high and low and have found no documentation with examples. First I thought maybe the code needs to free the query/connection results after calling the stored procedure, but of course MySQL++ doesn't have a free_result method... or does it? Anyways, here's what I've got: #include <iostream> #include <stdio.h> #include <queue> #include <deque> #include <sys/stat.h> #include <mysql++/mysql++.h> #include <boost/thread/thread.hpp> #include "RepositoryQueue.h" using namespace boost; using namespace mysqlpp; class RepositoryChecker { private: bool _isRunning; Connection _con; public: RepositoryChecker() { try { this->_con = Connection(false); this->_con.set_option(new MultiStatementsOption(true)); this->_con.set_option(new ReconnectOption(true)); this->_con.connect("**", "***", "***", "***"); this->ChangeRunningState(true); } catch(const Exception& e) { this->ChangeRunningState(false); } } /** * Thread method which runs and creates the repositories */ void CheckRepositoryQueues() { //while(this->IsRunning()) //{ std::queue<RepositoryQueue> queues = this->GetQueue(); if(queues.size() > 0) { while(!queues.empty()) { RepositoryQueue &q = queues.front(); char cmd[256]; sprintf(cmd, "svnadmin create /home/svn/%s/%s/%s", q.GetPublicStatus().c_str(), q.GetUsername().c_str(), q.GetRepositoryName().c_str()); if(this->DeleteQueuedRepository(q.GetQueueId())) { printf("query deleted?\n"); } printf("Repository created!\n"); queues.pop(); } } boost::this_thread::sleep(boost::posix_time::milliseconds(500)); //} } protected: /** * Gets the latest queue of repositories from the database * and returns them inside a cool queue defined with the * RepositoryQueue class. */ std::queue<RepositoryQueue> GetQueue() { std::queue<RepositoryQueue> queues; Query query = this->_con.query("CALL sp_GetRepositoryQueue();"); StoreQueryResult result = query.store(); RepositoryQueue rQ; if(result.num_rows() > 0) { for(unsigned int i = 0;i < result.num_rows(); ++i) { rQ = RepositoryQueue((unsigned int)result[i][0], (unsigned int)result[i][1], (String)result[i][2], (String)result[i][3], (String)result[i][4], (bool)result[i][5]); queues.push(rQ); } } return queues; } /** * Allows the thread to be shut off. */ void ChangeRunningState(bool isRunning) { this->_isRunning = isRunning; } /** * Returns the running value of the active thread. */ bool IsRunning() { return this->_isRunning; } /** * Deletes the repository from the mysql queue table. This is * only called once it has been created. */ bool DeleteQueuedRepository(unsigned int id) { char cmd[256]; sprintf(cmd, "DELETE FROM RepositoryQueue WHERE Id = %d LIMIT 1;", id); Query query = this->_con.query(cmd); return (query.exec()); } }; I've removed all the other methods as they're not needed... Basically it's the DeleteQueuedRepository method which isn't working, the GetQueue works fine. PS: This is on a Linux OS (Ubuntu server) Many thanks, Shaun

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• C - circular character buffer w/ pthreads

  - by Matt

  I have a homework assignment where I have to implement a circular buffer and add and remove chars with separate threads: #include <pthread.h> #include <stdio.h> #define QSIZE 10 pthread_cond_t full,/* count == QSIZE */ empty,/* count == 0 */ ready; pthread_mutex_t m, n; /* implements critical section */ unsigned int iBuf, /* tail of circular queue */ oBuf; /* head of circular queue */ int count; /* count characters */ char buf [QSIZE]; /* the circular queue */ void Put(char s[]) {/* add "ch"; wait if full */ pthread_mutex_lock(&m); int size = sizeof(s)/sizeof(char); printf("size: %d", size); int i; for(i = 0; i < size; i++) { while (count >= QSIZE) pthread_cond_wait(&full, &m);/* is there empty slot? */ buf[iBuf] = s[i]; /* store the character */ iBuf = (iBuf+1) % QSIZE; /* increment mod QSIZE */ count++; if (count == 1) pthread_cond_signal(&empty);/* new character available */ } pthread_mutex_unlock(&m); } char Get() {/* remove "ch" from queue; wait if empty */ char ch; pthread_mutex_lock(&m); while (count <= 0) pthread_cond_wait(&empty, &m);/* is a character present? */ ch = buf[oBuf]; /* retrieve from the head of the queue */ oBuf = (oBuf+1) % QSIZE; count--; if (count == QSIZE-1) pthread_cond_signal(&full);/* signal existence of a slot */ pthread_mutex_unlock(&m); return ch; } void * p1(void *arg) { int i; for (i = 0; i < 5; i++) { Put("hella"); } } void * p2(void *arg) { int i; for (i = 0; i < 5; i++) { Put("goodby"); } } int main() { pthread_t t1, t2; void *r1, *r2; oBuf = 0; iBuf = 0; count=0; /* all slots are empty */ pthread_cond_init(&full, NULL); pthread_cond_init(&empty, NULL); pthread_mutex_init(&m, NULL); pthread_create(&t1, NULL, p1, &r1); pthread_create(&t2, NULL, p2, &r2); printf("Main"); char c; int i = 0; while (i < 55) { c = Get(); printf("%c",c); i++; } pthread_join(t1, &r1); pthread_join(t2, &r2); return 0; } I shouldn't have to change the logic much at all, the requirements are pretty specific. I think my problem lies in the Put() method. I think the first thread is going in and blocking the critical section and causing a deadlock. I was thinking I should make a scheduling attribute? Of course I could be wrong. I am pretty new to pthreads and concurrent programming, so I could really use some help spotting my error.

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• Appropriate programming design questions.

  - by Edward

  I have a few questions on good programming design. I'm going to first describe the project I'm building so you are better equipped to help me out. I am coding a Remote Assistance Tool similar to TeamViewer, Microsoft Remote Desktop, CrossLoop. It will incorporate concepts like UDP networking (using Lidgren networking library), NAT traversal (since many computers are invisible behind routers nowadays), Mirror Drivers (using DFMirage's Mirror Driver (http://www.demoforge.com/dfmirage.htm) for realtime screen grabbing on the remote computer). That being said, this program has a concept of being a client-server architecture, but I made only one program with both the functionality of client and server. That way, when the user runs my program, they can switch between giving assistance and receiving assistance without having to download a separate client or server module. I have a Windows Form that allows the user to choose between giving assistance and receiving assistance. I have another Windows Form for a file explorer module. I have another Windows Form for a chat module. I have another Windows Form form for a registry editor module. I have another Windows Form for the live control module. So I've got a Form for each module, which raises the first question: 1. Should I process module-specific commands inside the code of the respective Windows Form? Meaning, let's say I get a command with some data that enumerates the remote user's files for a specific directory. Obviously, I would have to update this on the File Explorer Windows Form and add the entries to the ListView. Should I be processing this code inside the Windows Form though? Or should I be handling this in another class (although I have to eventually pass the data to the Form to draw, of course). Or is it like a hybrid in which I process most of the data in another class and pass the final result to the Form to draw? So I've got like 5-6 forms, one for each module. The user starts up my program, enters the remote machine's ID (not IP, ID, because we are registering with an intermediary server to enable NAT traversal), their password, and connects. Now let's suppose the connection is successful. Then the user is presented with a form with all the different modules. So he can open up a File Explorer, or he can mess with the Registry Editor, or he can choose to Chat with his buddy. So now the program is sort of idle, just waiting for the user to do something. If the user opens up Live Control, then the program will be spending most of it's time receiving packets from the remote machine and drawing them to the form to provide a 'live' view. 2. Second design question. A spin off question #1. How would I pass module-specific commands to their respective Windows Forms? What I mean is, I have a class like "NetworkHandler.cs" that checks for messages from the remote machine. NetworkHandler.cs is a static class globally accessible. So let's say I get a command that enumerates the remote user's files for a specific directory. How would I "give" that command to the File Explorer Form. I was thinking of making an OnCommandReceivedEvent inside NetworkHandler, and having each form register to that event. When the NetworkHandler received a command, it would raise the event, all forms would check it to see if it was relevant, and the appropriate form would take action. Is this an appropriate/the best solution available? 3. The networking library I'm using, Lidgren, provides two options for checking networking messages. One can either poll ReadMessage() to return null or a message, or one can use an AutoResetEvent OnMessageReceived (I'm guessing this is like an event). Which one is more appropriate?

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• How to design a C / C++ library to be usable in many client languages?

  - by Brian Schimmel

  I'm planning to code a library that should be usable by a large number of people in on a wide spectrum of platforms. What do I have to consider to design it right? To make this questions more specific, there are four "subquestions" at the end. Choice of language Considering all the known requirements and details, I concluded that a library written in C or C++ was the way to go. I think the primary usage of my library will be in programs written in C, C++ and Java SE, but I can also think of reasons to use it from Java ME, PHP, .NET, Objective C, Python, Ruby, bash scrips, etc... Maybe I cannot target all of them, but if it's possible, I'll do it. Requirements It would be to much to describe the full purpose of my library here, but there are some aspects that might be important to this question: The library itself will start out small, but definitely will grow to enormous complexity, so it is not an option to maintain several versions in parallel. Most of the complexity will be hidden inside the library, though The library will construct an object graph that is used heavily inside. Some clients of the library will only be interested in specific attributes of specific objects, while other clients must traverse the object graph in some way Clients may change the objects, and the library must be notified thereof The library may change the objects, and the client must be notified thereof, if it already has a handle to that object The library must be multi-threaded, because it will maintain network connections to several other hosts While some requests to the library may be handled synchronously, many of them will take too long and must be processed in the background, and notify the client on success (or failure) Of course, answers are welcome no matter if they address my specific requirements, or if they answer the question in a general way that matters to a wider audience! My assumptions, so far So here are some of my assumptions and conclusions, which I gathered in the past months: Internally I can use whatever I want, e.g. C++ with operator overloading, multiple inheritance, template meta programming... as long as there is a portable compiler which handles it (think of gcc / g++) But my interface has to be a clean C interface that does not involve name mangling Also, I think my interface should only consist of functions, with basic/primitive data types (and maybe pointers) passed as parameters and return values If I use pointers, I think I should only use them to pass them back to the library, not to operate directly on the referenced memory For usage in a C++ application, I might also offer an object oriented interface (Which is also prone to name mangling, so the App must either use the same compiler, or include the library in source form) Is this also true for usage in C# ? For usage in Java SE / Java EE, the Java native interface (JNI) applies. I have some basic knowledge about it, but I should definitely double check it. Not all client languages handle multithreading well, so there should be a single thread talking to the client For usage on Java ME, there is no such thing as JNI, but I might go with Nested VM For usage in Bash scripts, there must be an executable with a command line interface For the other client languages, I have no idea For most client languages, it would be nice to have kind of an adapter interface written in that language. I think there are tools to automatically generate this for Java and some others For object oriented languages, it might be possible to create an object oriented adapter which hides the fact that the interface to the library is function based - but I don't know if its worth the effort Possible subquestions is this possible with manageable effort, or is it just too much portability? are there any good books / websites about this kind of design criteria? are any of my assumptions wrong? which open source libraries are worth studying to learn from their design / interface / souce? meta: This question is rather long, do you see any way to split it into several smaller ones? (If you reply to this, do it as a comment, not as an answer)

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• [C#][Design] Appropriate programming design questions.

  - by Edward

  I have a few questions on good programming design. I'm going to first describe the project I'm building so you are better equipped to help me out. I am coding a Remote Assistance Tool similar to TeamViewer, Microsoft Remote Desktop, CrossLoop. It will incorporate concepts like UDP networking (using Lidgren networking library), NAT traversal (since many computers are invisible behind routers nowadays), Mirror Drivers (using DFMirage's Mirror Driver (http://www.demoforge.com/dfmirage.htm) for realtime screen grabbing on the remote computer). That being said, this program has a concept of being a client-server architecture, but I made only one program with both the functionality of client and server. That way, when the user runs my program, they can switch between giving assistance and receiving assistance without having to download a separate client or server module. I have a Windows Form that allows the user to choose between giving assistance and receiving assistance. I have another Windows Form for a file explorer module. I have another Windows Form for a chat module. I have another Windows Form form for a registry editor module. I have another Windows Form for the live control module. So I've got a Form for each module, which raises the first question: 1. Should I process module-specific commands inside the code of the respective Windows Form? Meaning, let's say I get a command with some data that enumerates the remote user's files for a specific directory. Obviously, I would have to update this on the File Explorer Windows Form and add the entries to the ListView. Should I be processing this code inside the Windows Form though? Or should I be handling this in another class (although I have to eventually pass the data to the Form to draw, of course). Or is it like a hybrid in which I process most of the data in another class and pass the final result to the Form to draw? So I've got like 5-6 forms, one for each module. The user starts up my program, enters the remote machine's ID (not IP, ID, because we are registering with an intermediary server to enable NAT traversal), their password, and connects. Now let's suppose the connection is successful. Then the user is presented with a form with all the different modules. So he can open up a File Explorer, or he can mess with the Registry Editor, or he can choose to Chat with his buddy. So now the program is sort of idle, just waiting for the user to do something. If the user opens up Live Control, then the program will be spending most of it's time receiving packets from the remote machine and drawing them to the form to provide a 'live' view. 2. Second design question. A spin off question #1. How would I pass module-specific commands to their respective Windows Forms? What I mean is, I have a class like "NetworkHandler.cs" that checks for messages from the remote machine. NetworkHandler.cs is a static class globally accessible. So let's say I get a command that enumerates the remote user's files for a specific directory. How would I "give" that command to the File Explorer Form. I was thinking of making an OnCommandReceivedEvent inside NetworkHandler, and having each form register to that event. When the NetworkHandler received a command, it would raise the event, all forms would check it to see if it was relevant, and the appropriate form would take action. Is this an appropriate/the best solution available? 3. The networking library I'm using, Lidgren, provides two options for checking networking messages. One can either poll ReadMessage() to return null or a message, or one can use an AutoResetEvent OnMessageReceived (I'm guessing this is like an event). Which one is more appropriate?

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• Future of VB.NET? [closed]

  - by Alex Yeung

  Hi all, I worked with C# for years. Last year, I changed my job and the company use VB.NET. Of course, theoretically C# and VB.NET are very similar and I easily adapted. However, I have worked for VB.NET for 1 year. I cannot see any future of VB.NET. As a programming language, it is so foo. Here is a list of what C# can do but VB.NET cannot Case insensitive variables how to think a new variable name? If I have a property called FolderPath, i need to establish another private variable called _folderPath or m_folderPath. In C#, FolderPath and folderPath are two variables. Moreover, it gets compile error if variable name is same as a class name. For example Dim guid = Guid.NewGuid(). (What the...) Again, I need to think a new variable name. Adhoc scope In C#, we could use {...} to create a adhoc scope and all resource in {...} will not affect the code outside. However there is not such syntax in VB.NET. I could only use If True Then and End If to make a local scope which is so unclear. In-Method Region Sometime, it is unavoidable to have a long long method. VB.NET does not support in-method region. I always need to scroll down for 1000 lines. It wastes my time. No multi-line string definition In C#, we could var s = @"..." to define a multi-line string. In VB.NET there is no direct method to do that. The indirect way is use XML-literal string. Dim s = <![CDATA[...]]>.Value. However it is unclear. No block comment In C#, we have line comment // and block comment /* ... */. However in VB.NET we only have line comment which is a very big trouble for me. No statement end symbol Statements are separated by line break in VB.NET; while statements are separated by ; in C#. Underscore I think many people know underscore _ is continue statement symbol. I really disagree with that. I know MS VB.NET language team is going to remove the underscore syntax from VB.NET. However what can we do now? Although underscore is removed in the future, what's the advantage of that? I cannot see any advantage! With scope With scope is an evil scope. Although it allows shorter statement, it is hard to trace. Default Namesapce in project level It is a nightmare for me. The only advantage of VB.NET is property initialization. I think C# cannot do that (correct me if I am wrong.) Public Property ThisIsMyProperty As String = "MyValue" Remarks: I don't think optional method parameters is an advantage of OOP. By those disadvantages, I cannot see the future of VB.NET. Anyone sees the future of VB.NET?

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• Formatting Telerik Chart and Legend Labels in Silverlight

  - by Bryan

  I am trying to format a column called 'Month' using the 3-character month abbreviation in my data grid which is bound to a bar chart. My grid and chart are based on this demo example: http://demos.telerik.com/silverlight/#Chart/Aggregates. Basically, the grid compiles data and summarizes by Year, Quarter, Month, and then some other categories as well. For the Month column, I tried two different methods (for sorting purposes, I have to use an integer or some date value for the month). First, I just made Month an integer field and then used a converter mapped in the xaml for the 'Month' field to display 'JAN', 'FEB', etc. This worked fine for the grid, but the chart would display 1, 2, etc. instead of the month abbreviation. I researched this and was not able to come up with a solution to map the converter to the chart. So, I tried making the Month field a datetime and then set the value to 1/1/1900, 2/1/1900, etc. and specified the format of the field to 'MMM' in the xaml for the grid. I then used the following statement to set the the format in the chart when the user grouped by month: SalesAnalysisChart.DefaultView.ChartArea.AxisX.DefaultLabelFormat = "MMM"; This partially worked in that when the months were displayed across the x-axis they were labeled properly, but not when they appeared in the legend (the user, of course, can group by any of the columns which may or may not include month). I've tried setting LegendItemLabelFormat, ItemLabelFormat, etc. but without success. I'm not sure of the element on which to set the property. I only need to change the default format for just the Month column - all other columns should display normally when grouped. I also came across a class called 'LegendItemFormatConverter' which looks promising but I can't find any examples as to how to implement it. I would actually prefer the converter method because the converter I wrote displays the month abbreviation in all caps, whereas the 'MMM' format displays in upper/lower case. Here is the converter code that I originally used for the grid: using System; using System.Net; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; using System.Windows.Ink; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Animation; using System.Windows.Shapes; using System.Windows.Data; namespace ApolloSL { public class MonthConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if (value != null) { DateTime date = new DateTime(1900, (Int32)value, 1); return date.ToString("MMM").ToUpper(); } else { return ""; } } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { return value.ToString(); } } } Please help... Thanks in advance for your assistance, Bryan

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• Limiting TCP sends with a "to-be-sent" queue and other design issues.

  - by Poni

  Hello all! This question is the result of two other questions I've asked in the last few days. I'm creating a new question because I think it's related to the "next step" in my understanding of how to control the flow of my send/receive, something I didn't get a full answer to yet. The other related questions are: http://stackoverflow.com/questions/3028376/an-iocp-documentation-interpretation-question-buffer-ownership-ambiguity http://stackoverflow.com/questions/3028998/non-blocking-tcp-buffer-issues In summary, I'm using Windows I/O Completion Ports. I have several threads that process notifications from the completion port. I believe the question is platform-independent and would have the same answer as if to do the same thing on a *nix, *BSD, Solaris system. So, I need to have my own flow control system. Fine. So I send send and send, a lot. How do I know when to start queueing the sends, as the receiver side is limited to X amount? Let's take an example (closest thing to my question): FTP protocol. I have two servers; One is on a 100Mb link and the other is on a 10Mb link. I order the 100Mb one to send to the other one (the 10Mb linked one) a 1GB file. It finishes with an average transfer rate of 1.25MB/s. How did the sender (the 100Mb linked one) knew when to hold the sending, so the slower one wouldn't be flooded? Another way to ask this: Can I get a "hold-your-sendings" notification from the remote side? Is it built-in in TCP or the so called "reliable network protocol" needs me to do so? Again, I have a loop with many sends to a remote server, and at some point, within that loop I'll have to determine if I should queue that send or I can pass it on to the transport layer (TCP). How do I do that? What would you do? Of course that when I get a completion notification from IOCP that the send was done I'll issue other pending sends, that's clear. Another design question related to this: Since I am to use a custom buffers with a send queue, and these buffers are being freed to be reused (thus not using the "delete" keyword) when a "send-done" notification has been arrived, I'll have to use a mutual exlusion on that buffer pool. Using a mutex slows things down, so I've been thinking; Why not have each thread have its own buffers pool, thus accessing it , at least when getting the required buffers for a send operation, will require no mutex, because it belongs to that thread only. The buffers pool is located at the thread local storage (TLS) level. No mutual pool implies no lock needed, implies faster operations BUT also implies more memory used by the app, because even if one thread already allocated 1000 buffers, the other one that is sending right now and need 1000 buffers to send something will need to allocated these to its own. This is a long question and I hope none got hurt (: Thank you all!

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• Using inheritance and polymorphism to solve a common game problem

  - by Barry Brown

  I have two classes; let's call them Ogre and Wizard. (All fields are public to make the example easier to type in.) public class Ogre { int weight; int height; int axeLength; } public class Wizard { int age; int IQ; int height; } In each class I can create a method called, say, battle() that will determine who will win if an Ogre meets and Ogre or a Wizard meets a Wizard. Here's an example. If an Ogre meets an Ogre, the heavier one wins. But if the weight is the same, the one with the longer axe wins. public Ogre battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else if (this.axeLength > o.axeLength) return this; else if (this.axeLength < o.axeLength) return o; else return this; // default case } We can make a similar method for Wizards. But what if a Wizard meets an Ogre? We could of course make a method for that, comparing, say, just the heights. public Wizard battle(Ogre o) { if (this.height > o.height) return this; else if (this.height < o.height) return o; else return this; } And we'd make a similar one for Ogres that meet Wizard. But things get out of hand if we have to add more character types to the program. This is where I get stuck. One obvious solution is to create a Character class with the common traits. Ogre and Wizard inherit from the Character and extend it to include the other traits that define each one. public class Character { int height; public Character battle(Character c) { if (this.height > c.height) return this; else if (this.height < c.height) return c; else return this; } } Is there a better way to organize the classes? I've looked at the strategy pattern and the mediator pattern, but I'm not sure how either of them (if any) could help here. My goal is to reach some kind of common battle method, so that if an Ogre meets an Ogre it uses the Ogre-vs-Ogre battle, but if an Ogre meets a Wizard, it uses a more generic one. Further, what if the characters that meet share no common traits? How can we decide who wins a battle?

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• jQuery hide/show with select tag

  - by Ozzy

  I'm relative new to jQuery and I've been asked to create a hide/show function with a select tag. The function pretty much would be when you click on one of the options in the select tag it will open a div associate with the div of course. To be honest I have no idea how approach this function. I need help urgently, I have already tried many online but none have seem to work. Find below the html code. Thanks. <div class="adwizard"> <select id="selectdrop" name="selectdrop" class="adwizard-bullet"> <option value="adwizard">AdWizard</option> <option value="collateral">Collateral Ordering Tool</option> <option value="ebrochure">eBrochures</option> <option value="brand">Brand Center</option> <option value="funtees">FunTees</option> </select> </div> <div class="panels"> <div id="adwizard" class="sub-box showhide"> <img src="../images/bookccl/img-adwizard.gif" width="95" height="24" alt="AdWizard" /> <p>Let Carnival help you grow your business with our great tools! Lor ipsum dolor sit amet. <a href="https://www.carnivaladwizard.com/home.asp">Learn More</a></p> </div> <div id="collateral" class="sub-box showhide"> <p>The Collateral Ordering Tool makes it easy for you to order destination brochures and the sales DVD for that upcoming event. <a href="http://carnival.litorders.com/workplace.asp">Learn More</a></p> </div> <div id="ebrochure" class="sub-box showhide"> <img src="../images/bookccl/img-ebrochure.gif" width="164" height="39" alt="Brochures" /> <p>Show your clients that you're listening to their specific vacation needs by delivering relevant planning info quickly. <a href="http://productiontrade.carnivalbrochures.com/start.aspx">Learn More</a></p> </div> <div id="brand" class="sub-box showhide"> <p>Carnival Brand Center is where you'll find information on our strategy, guidlines, templates and artwork. <a href="https://carnival.monigle2.net/user_info.asp?login_type=agent">Learn More</a></p> </div> <div id="funtees" class="sub-box showhide"> <img src="../images/bookccl/img-funtees.gif" width="164" height="39" alt="Funtees" /> <p>Create your very own Fun Design shirts to commemorate that special occasion aboard a Carnival "Fun Ship!" <a href="http://carnival.victorydyo.com/">Learn More</a></p> </div> </div><!-- ends .panel --> <a class="view" href="#">See All Marketing Tools</a> </div>

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• Wrapping a paragraph inside a div?

  - by LOD121

  How do I make my paragraph wrap inside my div? It is currently overflowing outside of the div and I have no idea how to stop the paragraph from overflowing over the edge. I do not want a scroll bar with: overflow: scroll; and the other overflow options don't seem to help here either... I have the following code: div { width: 1200px; margin: 0 auto; } .container { overflow: hidden; } .content { width: 1000px; float: left; margin-left: 0; text-align: left; } .rightpanel { width: 190px; float: right; margin-right: 0; } <div class="container"> <div class="content"> <p>Some content flowing over more than one line</p> </div> <div class="rightpanel"> <!-- content --> </div> </div> Edit: <div class="container"> <div class="content"> <div class="leftcontent"> </div> <div class="newsfeed"> <div class="newsitem"> <p>Full age sex set feel her told. Tastes giving in passed direct me valley as supply. End great stood boy noisy often way taken short. Rent the size our more door. Years no place abode in no child my. Man pianoforte too solicitude friendship devonshire ten ask. Course sooner its silent but formal she led. Extensive he assurance extremity at breakfast. Dear sure ye sold fine sell on. Projection at up connection literature insensible motionless projecting.<br><br>Be at miss or each good play home they. It leave taste mr in it fancy. She son lose does fond bred gave lady get. Sir her company conduct expense bed any. Sister depend change off piqued one. Contented continued any happiness instantly objection yet her allowance. Use correct day new brought tedious. By come this been in. Kept easy or sons my it done.</p> </div> </div> </div> <div class="rightpanel"> </div>

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