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  • Are there any examples of a temporal field/object updater?

    - by Bryan Agee
    The system in question has numerous examples of temporal objects and fields--ones which are a certain variable at a certain point in time. An example of this would be someone's rate of pay--there are different answers depending on when you ask and what the constraints might be; eg, can there ever be more than one of a certain temporal object concurrently, etc. Ideally, there would be an object that handles those constraints when a new state/stateful object is introduced; when a new value is set, it would prevent creating negative ranges and overlaps. Martin Fowler has written some great material on this (such as this description of Temporal Objects) , but what I've found of it tends to be entirely theoretic, with no concrete implementations. PHP is the target language, but examples in any language would be most helpful.

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  • How to present a stable data model in a public API that allows internal data structures to be changed without breaking the public view of the data?

    - by Max Palmer
    I am in the process of developing an application that allows users to write C# scripts. These scripts allow users to call selected methods and to access and manipulate data in a document. This works well, however, in the development version, scripts access the document's (internal) data structures directly. This means that if we were to change the internal data model/structure, there is a good chance that someone's script will no longer compile. We obviously want to prevent this breaking change from happening, but still want to allow the user to write sensible C# code (whilst not restricting how we develop our internal data model as a result). We therefore need to decouple our scripting API and its data structures from our internal methods and data structures. We've a few ideas as to how we might allow the user to access a what is effectively a stable public version of the document's internal data*, but I wanted to throw the question out there to someone who might have some real experience of this problem. NB our internal document's data structure is quite complex and it could be quite difficult to wrap. We know we want to expose as little as possible in our public API, especially as once it's out there, it's out there for good. Can anyone help? How do scripting languages / APIs decouple their public API and data structures from their internal data structures? Is there no real alternative to having to write a complex interaction layer? If we need to do this, what's a good approach or pattern for wrapping complex data structures that include nested objects, including collections? I've looked at the API facade pattern, which looks like it's trying to address these kinds of issues, but are there alternatives? *One idea is to build a data facade that is kept stable across versions of our application. The facade exposes a set of facade data objects that are used in the script code. These maintain backwards compatibility and wrap access to our internal document's data model.

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  • Languages/Methods to Learn for Scientific Computing?:

    - by Zéychin
    I'm a second-semester Junior working towards a Computer Science degree with a Scientific Computing concentration and a Mathematics degree with a concentration on Applied Discrete Mathematics. So, number crunching and such rather than a bunch of regular expressions, interface design, and networking. I've found that I'm not learning new relevant languages from my coursework and am interested in what the community would recommend me to learn. I know as far as programming methods go, I need to learn more about parallelizing programs, but if there's anything else you can recommend, I would appreciate it. Here's a list of the languages with which I am very experienced (web technologies omitted as they barely apply here). Any recommendations for additional languages I should learn would be very much appreciated!: Java C C++ Fortran77/90/95 Haskell Python MATLAB

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  • Managing Oracle Exalogic Elastic Cloud with Oracle Enterprise Manager Ops Center

    - by Anand Akela
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Oracle Enterprise Manager Ops Center 12c now comes out-of-the-box  with the latest release of Oracle Exalogic Elastic Cloud 2.0.1 software. It allows Customer to manage and monitor all components inside the Exalogic rack, including provisioning and management of physical and virtualized server. Ops Center will allow Customers to easily get started with creating and managing Private Clouds using the Exalogic components. Here is a snaphot of the Assets view showing the managable components of a Quarter Rack with 8 Compute Nodes: Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} A colleague has recently posted an interesting series of "Exalogic 2.0.1 Tea Break Snippets" which will guide you through the initial steps to get started with setting up your Exalogic environment: Exalogic 2.0.1 Tea Break Snippets - Creating Cloud Users https://blogs.oracle.com/ATeamExalogic/entry/exalogic_2_0_1_tea1 Exalogic 2.0.1 Tea Break Snippets - Creating Networks https://blogs.oracle.com/ATeamExalogic/entry/exalogic_2_0_1_tea2 Exalogic 2.0.1 Tea Break Snippets - Allocating Static IP Addresses https://blogs.oracle.com/ATeamExalogic/entry/exalogic_2_0_1_tea3 Exalogic 2.0.1 Tea Break Snippets - Creating Accounts https://blogs.oracle.com/ATeamExalogic/entry/exalogic_2_0_1_tea4 Exalogic 2.0.1 Tea Break Snippets - Importing Public Server Template https://blogs.oracle.com/ATeamExalogic/entry/exalogic_2_0_1_tea5 Have fun reading these very useful postings ! Dr. Jürgen Fleischer , Oracle Enterprise Manager Ops Center Engineering Stay Connected: Twitter |  Face book |  You Tube |  Linked in |  Newsletter

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  • Low coupling and tight cohesion

    - by hidayat
    Of course it depends on the situation. But when a lower lever object or system communicate with an higher level system, should callbacks or events be preferred to keeping a pointer to higher level object? For example, we have a world class that has a member variable vector<monster> monsters. When the monster class is going to communicate with the world class, should I prefer using a callback function then or should I have a pointer to the world class inside the monster class?

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  • Do the best developers look for a better job, or a better job finds them?

    - by Vasil Remeniuk
    As an example, one of the JavaPosse (popular Java podcast) hosts, Tor Norbey, has recently moved from Oracle to Google, and I'm more that sure that he has been lured (he definitely has not been sending his CV to Google). The rumor has it that 'high-level' developers are never hired through the job-sites. So, (given that you're a good developer) when you what to hold an appealing position in the company that interests you, and invest a lot of time into increasing your online-presence and self-branding blogging, twitting, contributing to opensource, actively participating in community sites (e.g., Stackoverflow), should you send your CVs here and there or just wait for proposals?

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  • OOP for unit testing : The good, the bad and the ugly

    - by Jeff
    I have recently read Miško Hevery's pdf guide to writing testable code in which its stated that you should limit your classes instanciations in your constructors. I understand that its what you should do because it allow you to easily mock you objects that are send as parameters to your class. But when it comes to writing actual code, i often end up with things like that (exemple is in PHP using Zend Framework but I think it's self explanatory) : class Some_class { private $_data; private $_options; private $_locale; public function __construct($data, $options = null) { $this->_data = $data; if ($options != null) { $this->_options = $options; } $this->_init(); } private function _init() { if(isset($this->_options['locale'])) { $locale = $this->_options['locale']; if ($locale instanceof Zend_Locale) { $this->_locale = $locale; } elseif (Zend_Locale::isLocale($locale)) { $this->_locale = new Zend_Locale($locale); } else { $this->_locale = new Zend_Locale(); } } } } Acording to my understanding of Miško Hevery's guide, i shouldn't instanciate the Zend_Local in my class but push it through the constructor (Which can be done through the options array in my example). I am wondering what would be the best practice to get the most flexibility for unittesing this code and aswell, if I want to move away from Zend Framework. Thanks in advance

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  • Advantages of Singleton Class over Static Class?

    Point 1) Singleton We can get the object of singleton and then pass to other methods. Static Class We can not pass static class to other methods as we pass objects Point 2) Singleton In future, it is easy to change the logic of of creating objects to some pooling mechanism. Static Class Very difficult to implement some pooling logic in case of static class. We would need to make that class as non-static and then make all the methods non-static methods, So entire your code needs to be changed. Point3:) Singleton Can Singletone class be inherited to subclass? Singleton class does not say any restriction of Inheritence. So we should be able to do this as long as subclass is also inheritence.There's nothing fundamentally wrong with subclassing a class that is intended to be a singleton. There are many reasons you might want to do it. and there are many ways to accomplish it. It depends on language you use. Static Class We can not inherit Static class to another Static class in C#. Think about it this way: you access static members via type name, like this: MyStaticType.MyStaticMember(); Were you to inherit from that class, you would have to access it via the new type name: MyNewType.MyStaticMember(); Thus, the new item bears no relationships to the original when used in code. There would be no way to take advantage of any inheritance relationship for things like polymorphism. span.fullpost {display:none;}

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  • Why should I use List<T> over IEnumerable<T>?

    - by Rowan Freeman
    In my ASP.net MVC4 web application I use IEnumerables, trying to follow the mantra to program to the interface, not the implementation. Return IEnumerable(Of Student) vs Return New List(Of Student) People are telling me to use List and not IEnumerable, because lists force the query to be executed and IEumerable does not. Is this really best practice? Is there any alternative? I feel strange using concrete objects where an interface could be used. Is my strange feeling justified?

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  • Do most programmers cut & paste code?

    - by John MacIntyre
    I learned very early on that cutting & pasting somebody else's code takes longer in the long run that writing it yourself. In my opinion unless you really understand it, cut & paste code will probably have issues which will be a nightmare to resolve. Don't get me wrong, I mean finding other peoples code and learning from it is essential, but we don't just paste it into our app. We rewrite the concepts into our app. But I'm constantly hearing about people who cut & paste, and they talk about it like it's common practice. I also see comments by others which indicate it's common practice. So, do most programmers cut & paste code?

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  • Pain of the Week/Expert's Perspective: Performance Tuning for Backups and Restores

    - by KKline
    First off - the Pain of the Week webcast series has been renamed. It's now known as The Expert's Perspective . Please join us for future webcasts and, if you're interested in speaking, drop me a note to see if we can get you on the roster! The bigger your databases get, the longer backups take. That doesn't really seem like a huge problem — until disaster strikes and you need to restore your databases as fast as possible. Join my buddy Brent Ozar ( blog | twitter ), a Microsoft Certified Master of...(read more)

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  • Publish/Subscribe/Request for exchange of big, complex, and confidential data?

    - by Morten
    I am working on a project where a website needs to exchange complex and confidential (and thus encrypted) data with other systems. The data includes personal information, technical drawings, public documents etc. We would prefer to avoid the Request-Reply pattern to the dependent systems (and there are a LOT of them), as that would create an awful lot of empty traffic. On the other hand, I am not sure that a pure Publisher/Subscriber pattern would be apropriate -- mainly because of the complex and bulky nature of the data to be exchanged. For that reason we have discussed the possibility of a "publish/subscribe/request" solution. The Publish/Subscribe part would be to publish a message to the dependent systems, that something is ready for pickup. The actual content is then picked up by old-school Request-Reply action. How does this sound to you?? Regards, Morten

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  • Changing the Game: Why Oracle is in the IT Operations Management Business

    - by DanKoloski
    v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif"; mso-bidi-font-family:"Times New Roman";} Next week, in Orlando, is the annual Gartner IT Operations Management Summit. Oracle is a premier sponsor of this annual event, which brings together IT executives for several days of high level talks about the state of operational management of enterprise IT. This year, Sushil Kumar, VP Product Strategy and Business Development for Oracle’s Systems & Applications Management, will be presenting on the transformation in IT Operations required to support enterprise cloud computing. IT Operations transformation is an important subject, because year after year, we hear essentially the same refrain – large enterprises spend an average of two-thirds (67%!) of their IT resources (budget, energy, time, people, etc.) on running the business, with far too little left over to spend on growing and transforming the business (which is what the business actually needs and wants). In the thirtieth year of the distributed computing revolution (give or take, depending on how you count it), it’s amazing that we have still not moved the needle on the single biggest component of enterprise IT resource utilization. Oracle is in the IT Operations Management business because when management is engineered together with the technology under management, the resulting efficiency gains can be truly staggering. To put it simply – what if you could turn that 67% of IT resources spent on running the business into 50%? Or 40%? Imagine what you could do with those resources. It’s now not just possible, but happening. This seems like a simple idea, but it is a radical change from “business as usual” in enterprise IT Operations. For the last thirty years, management has been a bolted-on afterthought – we pick and deploy our technology, then figure out how to manage it. This pervasive dysfunction is a broken cycle that guarantees high ongoing operating costs and low agility. If we want to break the cycle, we need to take a more tightly-coupled approach. As a complete applications-to-disk platform provider, Oracle is engineering management together with technology across our stack and hooking that on-premise management up live to My Oracle Support. Let’s examine the results with just one piece of the Oracle stack – the Oracle Database. Oracle began this journey with the Oracle Database 9i many years ago with the introduction of low-impact instrumentation in the database kernel (“tell me what’s wrong”) and through Database 10g, 11g and 11gR2 has successively added integrated advisory (“tell me how to fix what’s wrong”) and lifecycle management and automated self-tuning (“fix it for me, and do it on an ongoing basis for all my assets”). When enterprises take advantage of this tight-coupling, the results are game-changing. Consider the following (for a full list of public references, visit this link): British Telecom improved database provisioning time 1000% (from weeks to minutes) which allows them to provide a new DBaaS service to their internal customers with no additional resources Cerner Corporation Saved $9.5 million in CapEx and OpEx AND launched a brand-new cloud business at the same time Vodafone Group plc improved response times 50% and reduced maintenance planning times 50-60% while serving 391 million registered mobile customers Or the recent Database Manageability and Productivity Cost Comparisons: Oracle Database 11g Release 2 vs. SAP Sybase ASE 15.7, Microsoft SQL Server 2008 R2 and IBM DB2 9.7 as conducted by independent analyst firm ORC. In later entries, we’ll discuss similar results across other portions of the Oracle stack and how these efficiency gains are required to achieve the agility benefits of Enterprise Cloud. Stay Connected: Twitter |  Face book |  You Tube |  Linked in |  Newsletter

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  • What is required for a scope in an injection framework?

    - by johncarl
    Working with libraries like Seam, Guice and Spring I have become accustomed to dealing with variables within a scope. These libraries give you a handful of scopes and allow you to define your own. This is a very handy pattern for dealing with variable lifecycles and dependency injection. I have been trying to identify where scoping is the proper solution, or where another solution is more appropriate (context variable, singleton, etc). I have found that if the scope lifecycle is not well defined it is very difficult and often failure prone to manage injections in this way. I have searched on this topic but have found little discussion on the pattern. Is there some good articles discussing where to use scoping and what are required/suggested prerequisites for scoping? I interested in both reference discussion or your view on what is required or suggested for a proper scope implementation. Keep in mind that I am referring to scoping as a general idea, this includes things like globally scoped singletons, request or session scoped web variable, conversation scopes, and others. Edit: Some simple background on custom scopes: Google Guice custom scope Some definitions relevant to above: “scoping” - A set of requirements that define what objects get injected at what time. A simple example of this is Thread scope, based on a ThreadLocal. This scope would inject a variable based on what thread instantiated the class. Here's an example of this: “context variable” - A repository passed from one object to another holding relevant variables. Much like scoping this is a more brute force way of accessing variables based on the calling code. Example: methodOne(Context context){ methodTwo(context); } methodTwo(Context context){ ... //same context as method one, if called from method one } “globally scoped singleton” - Following the singleton pattern, there is one object per application instance. This applies to scopes because there is a basic lifecycle to this object: there is only one of these objects instantiated. Here's an example of a JSR330 Singleton scoped object: @Singleton public void SingletonExample{ ... } usage: public class One { @Inject SingeltonExample example1; } public class Two { @Inject SingeltonExample example2; } After instantiation: one.example1 == two.example2 //true;

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  • Google Programmers

    - by seth
    As a soon-to-be software engineer, I have studied some languages during my time in college. I can name C, C++, Java, Scheme, Ruby, PHP, for example. However, one of the main principles in my college (recognized by many as the best in my country) is to teach us how to learn for ourselves and how to search the web when we have a doubt. This leads to a proactive attitude, when I need something, I go get it and this has worked so far for me. Recently, I started wondering though, how much development would I be able to do without internet access. The answer bugged me quite a bit. I know the concept of the languages, mostly I know what to do, but I was amazed by how "slow" things were without having the google to help in the development. The problem was mostly related to specific syntax but it was not without some effort that i solved some of the SPOJ problems in C++. Is this normal? Should I be worried and try to change something in my programming behaviour? UPDATE: I'll give a concrete example. Reading and writing to a file in java. I have done this about a dozen times in my life, yet every time I need to do it, I end up googling "read file java" and refreshing my memory. I completely understand the code, i fully understand what it does. But I am sure, that without google, it would take me a few tries to read and write correctly (if I had to sit in front of the screen with a blank page and write this without consulting any source whatsoever).

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  • beginner - best way to do a 'Confirm' page? [closed]

    - by W_P
    I am a beginning web app developer, wondering about the best way to implement a "Confirm Page" upon form submission. I have heard that it's best for the script that a form POSTs to to be implemented by handling the POST data and then redirecting to another page, so the user isn't directly viewing the page that was POSTed to. My question is about the best way to implement a "Confirm before data save" page. Do I Have my form POST to a script, which marshals the data, puts in a GET, and redirects to the confirm page, which unmarshals and displays the data in another form, where the user can then either confirm (which causes another POST to a script that actually saves the data) or deny (which causes the user to be redirected back to the original form, with their input added)? Have my form POST directly to the confirm page, which is displayed to the user and then, like #1, gives the user the option to confirm or deny? Have my form GET the confirm page, which then does the expected behavior? I feel like there is a common-sense answer to this question that I am just not getting.

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  • Transiltion from maintenance programing to design

    - by andrew wang
    What to do guys do develop a design for a s/w for a given set of requirements? I like many people joined a Semiconductor MNC and got stuck in maintenance for quite a couple of years. My work was usually changing a lines of code for windows drivers supplied by my company or a couple of small script (style like) C programs for validating h/w. As a result I developed the bad habit of 'programming by coincidence'. I have not developed the ability for designing tools/programs from scratch. I was the only s/w member of the local team and thus some grunt work from the well established other site of the company came to be done by me. Now I have moved to a different company and thus finding developing from scratch very difficult. How do I unlearn my bad habit and develop this ability of designing s/w and then coding it ?

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  • How do I handle priority and propagation in an event system?

    - by Peeter
    Lets say I have a simple event system with the following syntax: object = new Object(); object.bind("my_trigger", function() { print "hello"; }); object.bind("my_trigger", function() { print "hello2"; }); object.trigger("my_trigger"); How could I make sure hello2 is printed out first (I do not want my code to depend on which order the events are binded). Ontop of that, how would I prevent my events from propagating (e.g. I want to stop every other event from being executed)

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  • Is it better to build HTML Code string on the server or on the client side?

    - by Ionut
    The result of the following process should be a html form. This form's structure varies from one to user. For example there might be a different number of rows or there may be the need for rowspan and colspan. When the user chooses to see this table an ajax call is made to the server where the structure of the table is decided from the database. Then I have to create the html code for the table structure which will be inserted in the DOM via JavaScript. The following problem comes to my mind: Where should I build the HTML code which will be inserted in the DOM? On the server side or should I send some parameters in the ajax call method and process the structure there? Therefore the main question involves good practice when it comes to decide between Server side processing or client side processing. Thank you!

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  • What does your Technical Documentation look like?

    - by Rachel
    I'm working on a large project and I would like to put together some technical documentation for other members of the team and for new programmers joining the project. What sort of documentation should I have? Just /// code comments or some other file(s) explaining the architechure and class design? I've never really done documentation except the occasional word doc to go with smaller apps, and I think this project is too large to doc in a single word file.

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  • Better solution then simple factory method when concrete implementations have different attributes

    - by danip
    abstract class Animal { function eat() {..} function sleep() {..} function isSmart() } class Dog extends Animal { public $blnCanBark; function isSmart() { return $this->blnCanBark; } } class Cat extends Animal { public $blnCanJumpHigh; function isSmart() { return $this->blnCanJumpHigh; } } .. and so on up to 10-20 animals. Now I created a factory using simple factory method and try to create instances like this: class AnimalFactory { public static function create($strName) { switch($strName) { case 'Dog': return new Dog(); case 'Cat': return new Cat(); default: break; } } } The problem is I can't set the specific attributes like blnCanBark, blnCanJumpHigh in an efficient way. I can send all of them as extra params to create but this will not scale to more then a few classes. Also I can't break the inheritance because a lot of the basic functionality is the same. Is there a better pattern to solve this?

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  • Should I provide fallbacks for HTML5/CSS3 elements in a web page at this point?

    - by Abluescarab
    I'm wondering if I should bother providing a fallback for HTML5 tags and attributes and CSS3 styling at this point in time. I know that there's probably still a lot of people out there who use older versions of browsers and HTML5/CSS3 are still fairly new. I read this article: Should I use non-standard tags in a HTML page for highlighting words? and one answer mentioned that people kind of "cheat" with older browsers by using the new tags and attributes, but styling them in CSS to ensure they show up right. This question: Relevance of HTML5: Is now the time? was asked about two years ago and I don't know how relevant it is anymore. For example, I want to use the placeholder and required attributes in a web form I'm building and it has no labels to show what each <input> is. How do I handle this, or do I bother?

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  • What is the meaning of 'high cohesion'?

    - by Max
    I am a student who recently joined a software development company as an intern. Back at the university, one of my professors used to say that we have to strive to achieve "Low coupling and high cohesion". I understand the meaning of low coupling. It means to keep the code of separate components separately, so that a change in one place does not break the code in another. But what is meant by high cohesion. If it means integrating the various pieces of the same component well with each other, I dont understand how that becomes advantageous. What is meant by high cohesion? Can an example be explained to understand its benefits?

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  • Trying to detect collision between two polygons using Separating Axis Theorem

    - by Holly
    The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(vertices[0]); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(vertices[i]); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if( other.x <= y || other.y >= x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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  • Interesting sessions/tips from RMOUG

    - by jean-pierre.dijcks
    One of the sessions I was at at last week's RMOUG was a session on Temp Tablespace Groups. I had a look because I had no experience with this and it seemed to help with parallel processing and the allocation/usage of temp. You can read the excellent write-up at Kellyn Pedersen's blog - who did the session and all the work - here. So for all of those who may be seeing lot's of waits like enq: TS - Contention when you are doing hash joins and sorts, do have a look at the above blog post. I also had the chance to listen in at Stewart Bryson's session on Restartability (he had 3 R-s) where he gave very useful tips about how to deal with your data warehouse loads. Questions like archive log mode - should I or should I not were well covered. Flashback archives, also nice to hear about. Very nice talk, very interesting. Unfortunately he hasn't blogged about it yes, so no pointers to that one. Got to see a couple of other interesting sessions, and as conferences go got to meet some interesting Oracle folks from the region. As usual RMOUG was useful and fun. Off to the drawing boards to design next year's session!

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