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  • pattern matching in .Net consistent with IsolatedStorageFile.GetFileNames() pattern matching

    - by Mick N
    Is the pattern matching logic used by this API exposed for reuse somewhere in the .Net Framework? Something of the form FilePatternMatch( string searchPattern, stringfileNameToTest ) is what I'm looking for. I'm implementing a temporary workaround for WP7 not filtering the results for this overload and I'd like the solution to both provide a consistent experience and avoid reinventing this functionality if it is exposed. If the behaviour is not exposed for reuse, a regular expression solution (like glob pattern matching in .NET) will suffice and would save me spending the time to test the fine details of what the behaviour should be. Perhaps one of the answers posted in the thread linked above is correct. Since I haven't confirmed the exact behaviour as yet, I wasn't able to determine this at a glance. Feel free to point me to one of those answers if you know it is behaviouraly an exact match to the API referenced in the question title. I could assume the pattern matching is consistent with how DOS handled * and ? in 8.3 file names (I'm familiar with behavioural nuances of that implementation), but it's reasonable to assume Microsoft has evolved pattern matching behaviour for file names in the decade+ since so I thought I would check before proceeding on that assumption.

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  • Lua pattern matching vs. regular expressions

    - by harald
    hello, i'm currently learning lua. regarding pattern-matching in lua i found the following sentence in the lua documentation on lua.org: Nevertheless, pattern matching in Lua is a powerful tool and includes some features that are difficult to match with standard POSIX implementations. as i'm familiar with posix regular expressions i would like to know if there are any common samples where lua pattern matching is "better" compared to regular expression -- or did i misinterpret the sentence? and if there are any common examples: why is any of pattern-matching vs. regular expressions better suited? thanks very much, harald

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  • Numerical Pattern Matching

    - by Timothy Strimple
    A project I'm researching requires some numerical pattern matching. My searches haven't turned up many relevant hits since most results tend to be around text pattern matching. The idea is we'll have certain wave patterns we'll need to be watching for and trying to match incoming data vs the wave database we will be building. Here is and example of one of the wave patterns we'll need to be matching against. There is clearly a pattern there, but the peaks will not have the exact same values, but the overall shape of the wave iterations will be very similar. Does anyone have any advice on how to go about storing and later matching these patterns, and / or other search terms I can use to find more information on the subject of pattern matching? Thanks, Tim.

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  • Pattern/Matcher in Java?

    - by user1007059
    I have a certain text in Java, and I want to use pattern and matcher to extract something from it. This is my program: public String getItemsByType(String text, String start, String end) { String patternHolder; StringBuffer itemLines = new StringBuffer(); patternHolder = start + ".*" + end; Pattern pattern = Pattern.compile(patternHolder); Matcher matcher = pattern.matcher(text); while (matcher.find()) { itemLines.append(text.substring(matcher.start(), matcher.end()) + "\n"); } return itemLines.toString(); } This code works fully WHEN the searched text is on the same line, for instance: String text = "My name is John and I am 18 years Old"; getItemsByType(text, "My", "John"); immediately grabs the text "My name is John" out of the text. However, when my text looks like this: String text = "My name\nis John\nand I'm\n18 years\nold"; getItemsByType(text, "My", "John"); It doesn't grab anything, since "My" and "John" are on different lines. How do I solve this?

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  • Design Pattern for "Context Sensitive" Right Click Menu

    - by MadSeb
    Hi, What is a design pattern I can use for generating "context-sensitive" right click menus ? I have in mind a "Windows Explorer"-like application where a user can right click on a folder and get a list of menu items but right click on a drive and get a totally different list. What design pattern should I use ? Would the factory design pattern be appropiate for handling such a menu ? Regards, Seb

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  • Video games, content strategy, and failure - oh my.

    - by Roger Hart
    Last night was the CS London group's event Content Strategy, Manhattan Style. Yes, it's a terrible title, feeling like a self-conscious grasp for chic, sadly commensurate with the venue. Fortunately, this was not commensurate with the event itself, which was lively, relevant, and engaging. Although mostly if you're a consultant. This is a strong strain in current content strategy discourse, and I think we're going to see it remedied quite soon. Not least in Paris on Friday. A lot of the bloggers, speakers, and commentators in the sphere are consultants, or part of agencies and other consulting organisations. A lot of the talk is about how you sell content strategy to your clients. This is completely acceptable. Of course it is. And it's actually useful if that's something you regularly have to do. To an extent, it's even portable to those of us who have to sell content strategy within an organisation. We're still competing for credibility and resource. What we're doing less is living in the beginning of a project. This was touched on by Jeffrey MacIntyre (albeit in a your-clients kind of a way) who described "the day two problem". Companies, he suggested, build websites for launch day, and forget about the need for them to be ongoing entities. Consultants, agencies, or even internal folks on short projects will live through Day Two quite often: the trainwreck moment where somebody realises that even if the content is right (which it often isn't), and on time (which it often isn't), it'll be redundant, outdated, or inaccurate by the end of the week/month/fickle social media attention cycle. The thing about living through a lot of Day Two is that you see a lot of failure. Nothing succeeds like failure? Failure is good. When it's structured right, it's an awesome tool for learning - that's kind of how video games work. I'm chewing over a whole blog post about this, but basically in game-like learning, you try, fail, go round the loop again. Success eventually yields joy. It's a relatively well-known phenomenon. It works best when that failing step is acutely felt, but extremely inexpensive. Dying in Portal is highly frustrating and surprisingly characterful, but the save-points are well designed and the reload unintrusive. The barrier to re-entry into the loop is very low, as is the cost of your failure out in meatspace. So it's easy (and fun) to learn. Yeah, spot the difference with business failure. As an external content strategist, you get to rock up with a big old folder full of other companies' Day Two (and ongoing day two hundred) failures. You can't send the client round the learning loop - although you may well be there because they've been round it once - but you can show other people's round trip. It's not as compelling, but it's not bad. What about internal content strategists? We can still point to things that are wrong, and there are some very compelling tools at our disposal - content inventories, user testing, and analytics, for instance. But if we're picking up big organically sprawling legacy content, Day Two may well be a distant memory, and the felt experience of web content failure is unlikely to be immediate to many people in the organisation. What to do? My hunch here is that the first task is to create something immediate and felt, but that it probably needs to be a success. Something quickly doable and visible - a content problem solved with a measurable business result. Now, that's a tall order; but scrape of the "quickly" and it's the whole reason we're here. At Red Gate, I've started with the text book fear and passion introduction to content strategy. In fact, I just typo'd that as "contempt strategy", and it isn't a bad description. Yelling "look at this, our website is rubbish!" gets you the initial attention, but it doesn't make you many friends. And if you don't produce something pretty sharp-ish, it's easy to lose the momentum you built up for change. The first thing I've done - after the visual content inventory - is to delete a bunch of stuff. About 70% of the SQL Compare web content has gone, in fact. This is a really, really cheap operation. It's visible, and it's powerful. It's cheap because you don't have to create any new content. It's not free, however, because you do have to validate your deletions. This means analytics, actually reading that content, and talking to people whose business purposes that content has to serve. If nobody outside the company uses it, and nobody inside the company thinks they ought to, that's a no-brainer for the delete list. The payoff here is twofold. There's the nebulous hard-to-illustrate "bad content does user experience and brand damage" argument; and there's the "nobody has to spend time (money) maintaining this now" argument. One or both are easily felt, and the second at least should be measurable. But that's just one approach, and I'd be interested to hear from any other internal content strategy folks about how they get buy-in, maintain momentum, and generally get things done.

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  • Most effective marketing strategy to promote a casual iOS game?

    - by user1114968
    So I posted this on another forum yesterday but that forum got suspended for malware so gotta wait for the webmaster to fix the site. Here's the basics: We've released a press release through PRMac that included a video review. Submitted and followed up on all the big iOS review sites. None of them replied back with interest. A lot of them just told me that their editors are volunteers who will review games that are "interesting to their readers" and that they would put my app "into consideration" The only site that reviewed our app and promoted virally was iPhoneAppReview.com which we paid. We promoted on the top iOS forums We are now doing in-app advertising through inMobi and are integrating the SDK code into our app to start doing Tapjoy We posted up our gameplay videos on YouTube Any marketing strategies that anyone can suggest or recommend that we haven't used yet? If anyone wants to try out our game and give feedback on the game or the site or anything, that would be great! Our target countries are Japan, China, and the US.

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  • RewriteRule Works With "Match Everything" Pattern But Not Directory Pattern

    - by kgrote
    I'm trying to redirect newsletter URLs from my local server to an Amazon S3 bucket. So I want to redirect from: https://mysite.com/assets/img/newsletter/Jan12_Newsletter.html to: https://s3.amazonaws.com/mybucket/newsletters/legacy/Jan12_Newsletter.html Here's the first part of my rule: RewriteEngine On RewriteBase / # Is it in the newsletters directory RewriteCond %{REQUEST_URI} ^(/assets/img/newsletter/)(.+) [NC] # Is not a 2008-2011 newsletter RewriteCond %{REQUEST_URI} !(.+)(11|10|09|08)_Newsletter.html$ [NC] ## -> RewriteRule to S3 Here <- ## If I use this RewriteRule to point to the new subdirectory on S3 it will NOT redirect: RewriteRule ^(/assets/img/newsletter/)(.+) https://s3.amazonaws.com/mybucket/newsletters/legacy/$2 [R=301,L] However if I use a blanket expression to capture the entire file path it WILL redirect: RewriteRule ^(.*)$ https://s3.amazonaws.com/mybucket/newsletters/legacy/$1 [R=301,L] Why does it only work with a "match everything" expression but not a more specific expression?

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  • would a composite design pattern be useful for group membership?

    - by changokun
    I'm trying to think about the best way to handle group memberships on a website. People sign up and select checkboxes in a list of interests. Every week we send out interest-themed emails to those members that indicated that interest. however i store the information in the database, while i am working with the lists and generating lists of email addresses or manipulating group memberships, the composite design pattern looked interesting. it would be easy to populate the group, then do some aggregating functions that say... generate the list of email addresses based on the interests. but i'm not sure i'm seeing any other advantages. i do need something scalable, and flexible. thoughts?

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  • Attempting to extract a pattern within a string

    - by Brian
    I'm attempting to extract a given pattern within a text file, however, the results are not 100% what I want. Here's my code: import java.util.regex.Matcher; import java.util.regex.Pattern; public class ParseText1 { public static void main(String[] args) { String content = "<p>Yada yada yada <code> foo ddd</code>yada yada ...\n" + "more here <2004-08-24> bar<Bob Joe> etc etc\n" + "more here again <2004-09-24> bar<Bob Joe> <Fred Kej> etc etc\n" + "more here again <2004-08-24> bar<Bob Joe><Fred Kej> etc etc\n" + "and still more <2004-08-21><2004-08-21> baz <John Doe> and now <code>the end</code> </p>\n"; Pattern p = Pattern .compile("<[1234567890]{4}-[1234567890]{2}-[1234567890]{2}>.*?<[^%0-9/]*>", Pattern.MULTILINE); Matcher m = p.matcher(content); // print all the matches that we find while (m.find()) { System.out.println(m.group()); } } } The output I'm getting is: <2004-08-24> bar<Bob Joe> <2004-09-24> bar<Bob Joe> <Fred Kej> <2004-08-24> bar<Bob Joe><Fred Kej> <2004-08-21><2004-08-21> baz <John Doe> and now <code> The output I want is: <2004-08-24> bar<Bob Joe> <2004-08-24> bar<Bob Joe> <2004-08-24> bar<Bob Joe> <2004-08-21> baz <John Doe> In short, the sequence of "date", "text (or blank)", and "name" must be extracted. Everything else should be avoided. For example the tag "Fred Kej" did not have any "date" tag before it, therefore, it should be flagged as invalid. Also, as a side question, is there a way to store or track the text snippets that were skipped/rejected as were the valid texts. Thanks, Brian

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  • How to improve the builder pattern?

    - by tangens
    Motivation Recently I searched for a way to initialize a complex object without passing a lot of parameter to the constructor. I tried it with the builder pattern, but I don't like the fact, that I'm not able to check at compile time if I really set all needed values. Traditional builder pattern When I use the builder pattern to create my Complex object, the creation is more "typesafe", because it's easier to see what an argument is used for: new ComplexBuilder() .setFirst( "first" ) .setSecond( "second" ) .setThird( "third" ) ... .build(); But now I have the problem, that I can easily miss an important parameter. I can check for it inside the build() method, but that is only at runtime. At compile time there is nothing that warns me, if I missed something. Enhanced builder pattern Now my idea was to create a builder, that "reminds" me if I missed a needed parameter. My first try looks like this: public class Complex { private String m_first; private String m_second; private String m_third; private Complex() {} public static class ComplexBuilder { private Complex m_complex; public ComplexBuilder() { m_complex = new Complex(); } public Builder2 setFirst( String first ) { m_complex.m_first = first; return new Builder2(); } public class Builder2 { private Builder2() {} Builder3 setSecond( String second ) { m_complex.m_second = second; return new Builder3(); } } public class Builder3 { private Builder3() {} Builder4 setThird( String third ) { m_complex.m_third = third; return new Builder4(); } } public class Builder4 { private Builder4() {} Complex build() { return m_complex; } } } } As you can see, each setter of the builder class returns a different internal builder class. Each internal builder class provides exactly one setter method and the last one provides only a build() method. Now the construction of an object again looks like this: new ComplexBuilder() .setFirst( "first" ) .setSecond( "second" ) .setThird( "third" ) .build(); ...but there is no way to forget a needed parameter. The compiler wouldn't accept it. Optional parameters If I had optional parameters, I would use the last internal builder class Builder4 to set them like a "traditional" builder does, returning itself. Questions Is this a well known pattern? Does it have a special name? Do you see any pitfalls? Do you have any ideas to improve the implementation - in the sense of fewer lines of code?

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  • BizTalk host throttling &ndash; Singleton pattern and High database size

    - by S.E.R.
    Originally posted on: http://geekswithblogs.net/SERivas/archive/2013/06/30/biztalk-host-throttling-ndash-singleton-pattern-and-high-database-size.aspxI have worked for some days around the singleton pattern (for those unfamiliar with it, read this post by Victor Fehlberg) and have come across a few very interesting posts, among which one dealt with performance issues (here, also by Victor Fehlberg). Simply put: if you have an orchestration which implements the singleton pattern, then performances will continuously decrease as the orchestration receives and consumes messages, and that behavior is more obvious when the orchestration never ends (ie : it keeps looping and never terminates or completes). As I experienced the same kind of problem (actually I was alerted by SCOM, which told me that the host was being throttled because of High database size), I thought it would be a good idea to dig a little bit a see what happens deep inside BizTalk and thus understand the reasons for this behavior. NOTE: in this article, I will focus on this High database size throttling condition. I will try and work on the other conditions in some not too distant future… Test conditions The singleton orchestration For the purpose of this study, I have created the following orchestration, which is a very basic implementation of a singleton that piles up incoming messages, then does something else when a certain timeout has been reached without receiving another message: Throttling settings I have two distinct hosts : one that hosts the receive port (basic FILE port) : Ports_ReceiveHostone that hosts the orchestration : ProcessingHost In order to emphasize the throttling mechanism, I have modified the throttling settings for each of these hosts are as follows (all other parameters are set to the default value): [Throttling thresholds] Message count in database: 500 (default value : 50000) Evolution of performance counters when submitting messages Since we are investigating the High database size throttling condition, here are the performance counter that we should take a look at (all of them are in the BizTalk:Message Agent performance object): Database sizeHigh database sizeMessage delivery throttling stateMessage publishing throttling stateMessage delivery delay (ms)Message publishing delay (ms)Message delivery throttling state durationMessage publishing throttling state duration (If you are not used to Perfmon, I strongly recommend that you start using it right now: it is a wonderful tool that allows you to open the hood and see what is going on inside BizTalk – and other systems) Database size It is quite obvious that we will start by watching the database size and high database size counters, just to see when the first reaches the configured threshold (500) and when the second rings the alarm. NOTE : During this test I submitted 600 messages, one message at a time every 10ms to see the evolution of the counters we have previously selected. It might not show very well on this screenshot, but here is what happened: From 15:46:50 to 15:47:50, the database size for the Ports_ReceiveHost host (blue line) kept growing until it reached a maximum of 504.At 15:47:50, the high database size alert fires At first I was surprised by this result: why is it the database size of the receiving host that keeps growing since it is the processing host that piles up messages? Actually, it makes total sense. This counter measures the size of the database queue that is being filled by the host, not consumed. Therefore, the high database size alert is raised on the host that fills the queue: Ports_ReceiveHost. More information is available on the Public MPWiki page. Now, looking at the Message publishing throttling state for the receiving host (green line), we can see that a throttling condition has been reached at 15:47:50: We can also see that the Message publishing delay(ms) (blue line) has begun growing slowly from this point. All of this explains why performances keep decreasing when a singleton keeps processing new messages: the database size grows and when it has exceeded the Message count in database threshold, the host is throttled and the publishing delay keeps increasing. Digging further So, what happens to the database queue then? Is it flushed some day or does it keep growing and growing indefinitely? The real question being: will the host be throttled forever because of this singleton? To answer this question, I set the Message count in database threshold to 20 (this value is very low in order not to wait for too long, otherwise I certainly would have fallen asleep in front of my screen) and I submitted 30 messages. The test was started at 18:26. At 18:56 (ie : exactly 30min later) the throttling was stopped and the database size was divided by 2. 30 min later again, the database size had dropped to almost zero: I guess I’ll have to find some documentation and do some more testing before I sort this out! My guess is that some maintenance job is at work here, though I cannot tell which one Digging even further If we take a look at the Message delivery throttling state counter for the processing host, we can see that this host was also throttled during the submission of the 600 documents: The value for the counter was 1, meaning that Message delivery incoming rate for the host instance exceeds the Message delivery outgoing rate * the specified Rate overdrive factor (percent) value. We will see this another day… :) A last word Let’s end this article with a warning: DO NOT CHANGE THE THROTTLING SETTINGS LIGHTLY! The temptation can be great to just bypass throttling by setting very high values for each parameter (or zero in some cases, which simply disables throttling). Nevertheless, always keep in mind that this mechanism is here for a very good reason: prevent your BizTalk infrastructure from exploding!! So whatever you do with those settings, do a lot of testing and benchmarking!

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  • Multi-Threading - Cleanup strategy at program end

    - by weismat
    What is the best way to finish a multi-threaded application in a clean way? I am starting several socket connections from the main thread in seperate sockets and wait until the end of my business day in the main thread and use currently System.Environment.Exit(0) to terminate it. This leads to an unhandled execption in one of the childs. Should I stop the threads from the list? I have been reluctant to implement any real stopping in the childs yet, thus I am wondering about the best practice. The sockets are all wrapped nicely with proper destructors for logging out and closing, but it still leads to errors.

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  • Clarification on the Strategy Pattern

    - by Holly
    I've just been reading through some basic design patterns, Could someone tell me if the term "strategy pattern" only applies if your implementing a completely abstract interface? What about when your children (concretes?) inherit from a parent class (the strategy?) with some implemented methods and some virtual and/or abstract functions? Otherwise the rest of the implementation, the idea that you can switch between different children at run time, is identical. This is something i'm quite familiar with, i was wondering if you would still call it the Strategy Pattern or if that term only applies to using an interface. Apologies if this question is not appropriate! Or if this is just nitpicking :) I'm still learning and i'm not really sure if design patterns are quite heavily defined within the industry or just a concept to be implemented as you like.

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  • Repository pattern - Switch out the database and switch in XML files

    - by glasto red
    Repository pattern - Switch out the database and switch in XML files. Hello I have an asp.net MVC 2.0 project and I have followed the Repository pattern. Periodically, I am losing access to the database server so I want to have another mechanism in place (XML files) to continue developing. It is not possible to have a local version of the db unfortunately! I thought this would be relatively easy using the Repository pattern, to switch out the db repositories and switch in XML versions. However, I am having real trouble coming up with a solution. I have tried LinqToXML but then ran into problems trying to return a List of News items as the LinqToXML ToList returns Generic.List Should I be mapping the XElement list over to the News list by hand? It just seems a bit clunky compared to LinqToSQL attributes on the News class and then simply doing a Table.....ToList(); Any direction would be appreciated. Thanks

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  • Scala wont pattern match with java.lang.String and Case Class

    - by Stefan
    Hello fellow Scala Programmers I have been working with Scala for some month now, however I have a problem with some properly basic stuff, I am hoping you will help my out with it. case class PersonClass(name: String, age: Int) object CaseTester { def main(args:Array[String]) { val string = "hej" string match { case e:String => println(string) case PersonClass => println(string) } } } When I am doing like this I get error: pattern type is incompatible with expected type; found : object PersonClass required: java.lang.String case PersonClass = println(string) And if I then change the second line in the pattern matching to the following: case e:PersonClass => println(string) I then get the error: error: scrutinee is incompatible with pattern type; found : PersonClass required: java.lang.String case e:PersonClass = println(string) However if I change the string definition to the following it compiles fine in both cases. val string:AnyRef = "hej"

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  • Mapping to a JSON method with url-pattern

    - by Brian
    I'm creating a Spring MVC application that will have a controller with 'RequestMapping'-annotated methods, including a JSON method. It currently has static content that resides in webapps/static, and the app itself resides in webapps/myapp. I assume that Catalina's default servlet is handling the static content, and my *.htm url-pattern in web.xml is returning the request for my JSP page, but I haven't been able to get the JSON method to be called. How do I write the url-pattern in the servlet mapping to do so? Using /* has not worked; it prevents the app from being accessed at all. Is there anything else to be aware of? EDIT: The url-pattern '/' appears to allow the JSON request through, because a 406 error is returned. What then would need to be modified to allow JSON to be returned?

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  • Using the Module Pattern for larger projects

    - by Rob
    I'm interested in using the Module Pattern to better organize my future projects. Unfortunately, there are only a few brief tutorials and proof-of-concept examples of the Module Pattern. Using the module pattern, I would like to organize projects into this sort of structure: project.arm.object.method(); Where "project" is my global project name, "arm" is a sub-section or branch of the project, "object" is an individual object, and so on to the methods and properties. However, I'm not sure how I should be declaring and organizing multiple "arms" and "objects" under "project". var project = window.project || {}; project.arm = project.arm || {}; project.arm.object = (function() { var privateVar = "Private contents."; function privateMethod() { alert(privateVar); } return { method: privateMethod }; }()); Are there any best practices or conventions when defining a complex module structure? Should I just declare a new arm/object underneath the last?

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  • Javascript: Using the Module Pattern for larger projects

    - by Rob
    I'm interested in using the Module Pattern to better organize my future projects. Unfortunately, there are only a few brief tutorials and proof-of-concept examples of the Module Pattern. Using the module pattern, I would like to organize projects into this sort of structure: project.arm.object.method(); Where "project" is my global project name, "arm" is a sub-section or branch of the project, "object" is an individual object, and so on to the methods and properties. However, I'm not sure how I should be declaring and organizing multiple "arms" and "objects" under "project". var project = window.project || {}; project.arm = project.arm || {}; project.arm.object = (function() { var privateVar = "Private contents."; function privateMethod() { alert(privateVar); } return { method: privateMethod }; }()); Are there any best practices or conventions when defining a complex module structure? Should I just declare a new arm/object underneath the last?

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  • Is it possible, with simple F# pattern matching transformations, to ignore unmatched values without

    - by Phobis
    So, I previously asked this question: http://stackoverflow.com/questions/2820234/can-someone-help-me-compare-using-f-over-c-in-this-specific-example-ip-address I was looking at the posted code and I was wondering if this code could be written without it producing a warning: let [|a;b;c;d|] = s.Split [|'.'|] IP(parseOrParts a, parseOrParts b, parseOrParts c, parseOrParts d) Is it possible to do something for the match _ pattern ot ignore? Without adding in something like Active Patterns? i want to keep the code as simple as possible... can I do this without drastically changing this code? NOTE: Warning is as follows Warning Incomplete pattern matches on this expression. For example, the value '[|_; _; _; _; _|]' may indicate a case not covered by the pattern(s).

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  • What is this Design Pattern?

    - by Can't Tell
    I read the Wikipedia articles on FactoryMethod and AbstractFactory but the following code doesn't seem to fit anywhere. Can someone explain to me what the following pattern is or if it is an anti-pattern? interace PaymentGateway{ void makePayment(); } class PaypalPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class AuthorizeNetPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class PaymentGatewayFacotry{ PaymentGateway createPaymentGateway(int gatewayId) { if(gatewayId == 1) return PaypalPaymentGateway(); else if(gatewayId == 2) return AuthorizeNetPaymentGateway(); } } Let's say the user selects the payment method using a radio button on an html page and the gatewayId is derived from the radio button value. I have seen code like this and thought it was the AbstractFactory pattern but after reading the Wikipedia article, I'm having doubts.

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  • Is the Observer pattern adequate for this kind of scenario?

    - by Omega
    I'm creating a simple game development framework with Ruby. There is a node system. A node is a game entity, and it has position. It can have children nodes (and one parent node). Children are always drawn relatively to their parent. Nodes have a @position field. Anyone can modify it. When such position is modified, the node must update its children accordingly to properly draw them relatively to it. @position contains a Point instance (a class with x and y properties, plus some other useful methods). I need to know when a node's @position's state changes, so I can tell the node to update its children. This is easy if the programmer does something like this: @node.position = Point.new(300,300) Because it is equivalent to calling this: # Code in the Node class def position=(newValue) @position = newValue update_my_children # <--- I know that the position changed end But, I'm lost when this happens: @node.position.x = 300 The only one that knows that the position changed is the Point instance stored in the @position property of the node. But I need the node to be notified! It was at this point that I considered the Observer pattern. Basically, Point is now observable. When a node's position property is given a new Point instance (through the assignment operator), it will stop observing the previous Point it had (if any), and start observing the new one. When a Point instance gets a state change, all observers (the node owning it) will be notified, so now my node can update its children when the position changes. A problem is when this happens: @someNode.position = @anotherNode.position This means that two nodes are observing the same point. If I change one of the node's position, the other would change as well. To fix this, when a position is assigned, I plan to create a new Point instance, copy the passed argument's x and y, and store my newly created point instead of storing the passed one. Another problem I fear is this: somePoint = @node.position somePoint.x = 500 This would, technically, modify @node's position. I'm not sure if anyone would be expecting that behavior. I'm under the impression that people see Point as some kind of primitive rather than an actual object. Is this approach even reasonable? Reasons I'm feeling skeptical: I've heard that the Observer pattern should be used with, well, many observers. Technically, in this scenario there is only one observer at a time. When assigning a node's position as another's (@someNode.position = @anotherNode.position), where I create a whole new instance rather than storing the passed point, it feels hackish, or even inefficient.

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  • OOW content for Pattern Matching....

    - by KLaker
    If you missed my sessions at OpenWorld then don't worry - all the content we used for pattern matching (presentation and hands-on lab) is now available for download. My presentation "SQL: The Best Development Language for Big Data?" is available for download from the OOW Content Catalog, see here: https://oracleus.activeevents.com/2013/connect/sessionDetail.ww?SESSION_ID=9101 For the hands-on lab ("Pattern Matching at the Speed of Thought with Oracle Database 12c") we used the Oracle-By-Example content. The OOW hands-on lab uses Oracle Database 12c Release 1 (12.1) and uses the MATCH_RECOGNIZE clause to perform some basic pattern matching examples in SQL. This lab is broken down into four main steps: Logically partition and order the data that is used in the MATCH_RECOGNIZE clause with its PARTITION BY and ORDER BY clauses. Define patterns of rows to seek using the PATTERN clause of the MATCH_RECOGNIZE clause. These patterns use regular expressions syntax, a powerful and expressive feature, applied to the pattern variables you define. Specify the logical conditions required to map a row to a row pattern variable in the DEFINE clause. Define measures, which are expressions usable in the MEASURES clause of the SQL query. You can download the setup files to build the ticker schema and the student notes from the Oracle Learning Library. The direct link to the example on using pattern matching is here: http://apex.oracle.com/pls/apex/f?p=44785:24:0::NO:24:P24_CONTENT_ID,P24_PREV_PAGE:6781,2.

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