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  • Reusable VS clean code - where's the balance?

    - by Radek Šimko
    Let's say I have a data model for a blog posts and have two use-cases of that model - getting all blogposts and getting only blogposts which were written by specific author. There are basically two ways how I can realize that. 1st model class Articles { public function getPosts() { return $this->connection->find() ->sort(array('creation_time' => -1)); } public function getPostsByAuthor( $authorUid ) { return $this->connection->find(array('author_uid' => $authorUid)) ->sort(array('creation_time' => -1)); } } 1st usage (presenter/controller) if ( $GET['author_uid'] ) { $posts = $articles->getPostsByAuthor($GET['author_uid']); } else { $posts = $articles->getPosts(); } 2nd one class Articles { public function getPosts( $authorUid = NULL ) { $query = array(); if( $authorUid !== NULL ) { $query = array('author_uid' => $authorUid); } return $this->connection->find($query) ->sort(array('creation_time' => -1)); } } 2nd usage (presenter/controller) $posts = $articles->getPosts( $_GET['author_uid'] ); To sum up (dis)advantages: 1) cleaner code 2) more reusable code Which one do you think is better and why? Is there any kind of compromise between those two?

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  • C# development with Mono and MonoDevelop

    - by developerit
    In the past two years, I have been developing .NET from my MacBook by running Windows XP into VM Ware and more recently into Virtual Box from OS X. This way, I could install Visual Studio and be able to work seamlessly. But, this way of working has a major down side: it kills the battery of my laptop… I can easiely last for 3 hours if I stay in OS X, but can only last 45 min when XP is running. Recently, I gave MonoDevelop a try for developing Developer IT‘s tools and web site. While being way less complete then Visual Studio, it provides essentials tools when it comes to developping software. It works well with solutions and projects files created from Visual Studio, it has Intellisence (word completion), it can compile your code and can even target your .NET app to linux or unix. This tools can save me a lot of time and batteries! Although I could not only work with MonoDevelop, I find it way better than a simple text editor like Smultron. Thanks to Novell, we can now bring Microsoft technology to OS X.

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  • Shared Development Space

    - by PatrickWalker
    Currently the company I work in gives each developer their own development virtual machine. On this machine (Windows 7) they install the entire stack of the product (minus database) this stack is normally spread amongst multiple machines of differing OS (although moving towards windows 2008 and 2008r2) So when a developer has a new project they are likely to be updating only a small piece of their stack and as such the rest of it can become out of date with the latest production code. The isolation from others means some issues won't be found until the code goes into shared test environments/production. I'm suggesting a move from functional testing on these isolated machines to plugging machines into a shared environment. The goal being to move towards a deployment thats closer to production in mechanism and server type. Developers would still make code changes on their Win7 vm and run unit/component testing locally but for functionally testing they would leverage a shared enviornment. Does anyone else use a shared development environment like this? Are there many reasons against this sort of sandbox environment? The biggest drawback is a move away from only checking in code when you've done local functional testing to checking in after static testing. I'm hoping an intelligent git branching strategy can take care of this for us.

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  • Does code-generation increase the code quality?

    - by platzhirsch
    Arguing for code-generation I am looking for some reasons, if howsoever, code generation increases the code quality, respectively is in favor for quality insurance. To clarify what I mean with code-generation I can talk only about a project of mine: We use XML files to describe different relationships, in fact our database schema. These XML files are used to generate our ORM framework and HTML forms which can be used to add, delete and modify entities. To my mind, it increases the quality, as the human error is reduced. If someone was implemented wrong, it is broken in the model. This is good, because the error might appear a lot faster, as more generated code is broken, too.

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  • Code Review tools - to use or not?

    - by liortal
    On my dev team, we're doing code reviews, however not in a proper way i believe. The issues our process suffers from: Not enough time is allocated for proper code review. Doing reviews is not mandatory - many times it is simply not done. Devs sit together for reviews, due to lack of another easy mechanism for doing it "offline" without spending both developers' time. My question is: can integration of a tool for code reviews improve the points mentioned above? Is it not needed? I would love to hear from positive/negative experiences.

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  • code metrics for .net code

    - by user20358
    While the code metrics tool gives a pretty good analysis of the code being analyzed, I was wondering if there was any such benchmark on acceptable standards for the following as well: Maximum number of types per assembly Maximum number of such types that can be accessible Maximum number of parameters per method Acceptable RFC count Acceptable Afferent coupling count Acceptable Efferent coupling count Any other metrics to judge the quality of .Net code by? Thanks for your time.

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  • What code smell best describes this code?

    - by Paul Stovell
    Suppose you have this code in a class: private DataContext _context; public Customer[] GetCustomers() { GetContext(); return _context.Customers.ToArray(); } public Order[] GetOrders() { GetContext(); return _context.Customers.ToArray(); } // For the sake of this example, a new DataContext is *required* // for every public method call private void GetContext() { if (_context != null) { _context.Dispose(); } _context = new DataContext(); } This code isn't thread-safe - if two calls to GetOrders/GetCustomers are made at the same time from different threads, they may end up using the same context, or the context could be disposed while being used. Even if this bug didn't exist, however, it still "smells" like bad code. A much better design would be for GetContext to always return a new instance of DataContext and to get rid of the private field, and to dispose of the instance when done. Changing from an inappropriate private field to a local variable feels like a better solution. I've looked over the code smell lists and can't find one that describes this. In the past I've thought of it as temporal coupling, but the Wikipedia description suggests that's not the term: Temporal coupling When two actions are bundled together into one module just because they happen to occur at the same time. This page discusses temporal coupling, but the example is the public API of a class, while my question is about the internal design. Does this smell have a name? Or is it simply "buggy code"?

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  • Web application development over C++ development..

    - by learnerforever
    Hi, I am CS undergrad and CS grad. In college I used to program in C/C++/java and have pretty much stuck to the same skill set in industry with 3 years experience. I like thinking,reading,applying logic etc, designing data structures, but I have little patience with debugging large C++ code. And having to deal with low level stuff like memory fault,memory corruption,compilation/linking issues. My confidence in programming is getting down due to this, but I like being in technical field. Does web application development like LAMP suit (Linux,apache,mysql,php),CSS,scripting (AMONG OTHER WEB DEVELOPMENT RELATED SKILLS) etc need lesser patience with debugging,and understanding of low level stuff, but your analysis/logical skills also get used? Also opportunities in web application development look more. Things like scalability, most of the stuff that Google does fascinates me, but for patience needed for dealing with C++ debugging. I make blunders while coding. How does the field look like outside C++? I am beginning to wonder if as a female, by moving to web application development, I can better manage work life balance. I have seen relatively lesser females in C++ than in Java/.net. Not very sure about web related stuff though. Also, what are the other hot technologies being used in web application development? lamp,css is something I know vaguely. Not in touch with keywords going on in this area. Please help!!.

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  • Java code critique request [closed]

    - by davidk01
    Can you make sense of the following bit of java code and do you have any suggestions for improving it? Instead of writing four almost identical setOnClickListener method calls I opted to iterate over an array but I'm wondering if this was the best way to do it. Here's the code: /* Set up the radio button click listeners so two categories are not selected at the same time. When one of them is clicked it clears the others. */ final RadioButton[] buttons = {radio_books,radio_games,radio_dvds,radio_electronics}; for (int i = 0; i < 4; i++) { final int k = i; buttons[i].setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { for (int j = 0; j < 4; j++) { if (buttons[j] != buttons[k]) { buttons[j].setChecked(false); } } } }); }

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  • Mobile Development- Obtaining development hardware - best practices?

    - by Zoot
    I'm looking to get into smartphone development, but there a quite a few options out there for platforms right now. (iOS/Android/WebOS/Bada/Symbian/MeeGo/WindowsMobile/JavaME) I'd like to have development hardware to test my code and the overall functionality of the devices. What is the best way to obtain and/or borrow hardware for development and testing? Are there rules of thumb to follow which apply to all companies and platforms? In this situation, I'm a single developer. Does this process change for a startup? A hackerspace? A small business? A large business? Thanks.

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  • Should we enforce code style in our large codebase?

    - by eighttrackmind
    By "code style" I mean 2 things: Style, eg. // bad if(foo){ ... } // good if (foo) { ... } Conventions and idiomaticity, where two ways of writing the same thing are functionally equivalent, but one is more idiomatic. eg. // bad if (fooLib.equals(a, b)) { ... } // good if (a == b) { ... } I think it makes sense to use an auto-formatter to enforce #1 automatically. So my question is specifically about #2. I like to break things down into pros and cons, here's what I've come up with so far: Pros: Used by many large codebases (eg. Google, jQuery) Helps make it a bit easier to work on new areas of the codebase Helps make code more portable (this is not necessarily true) Code style is automatic once you get used to it Makes it easier to fast-decline pull requests Cons: Takes engineers’ and code reviewers’ time away from more important things (like developing features) Code should ideally be rewritten every 2-3 years anyway, so it’s more important to focus on getting the architecture right, and achieving high test coverage Adds strain to code reviews (eg. “don’t do it this way, I like this other way better”) Even if I’ve been using a code style for a while, I still sometime have to pause and think about how to write a line better Having an enforced, uniform code style makes it hard to experiment with potentially better styles Maintaining a style guide takes a lot of incremental effort Engineers rarely read through the style guide. More often, it's cited in code reviews And as a secondary question: we also have many smaller repositories - should the same code style be enforced there?

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  • Trade-offs of local vs remote development workflows for a web development team

    - by lamp_scaler
    We currently have SVN setup on a remote development server. Developers SSH into the server and develops on their sandbox environment on the server. Each one has a virtual host pointed to their sandbox so they can preview their changes via the web browser by connecting to developer-sandbox1.domain.com. This has worked well so far because the team is small and everyone uses computers with varying specs and OSs. I've heard some web shops are using a workflow that has the developers work off of a VM on their local machine and then finally push changes to the remote server that hosts SVN. The downside to this is that everyone will need to make sure their machine is powerful enough to run both the VM and all their development tools. This would also mean creating images that mirror the server environment (we use CentOS) and have them install it into their VMs. And this would mean creating new images every time there is an update to the server environment. What are some other trade-offs? Ultimately, why did you choose one workflow over the other?

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  • Web versus desktop development - is web development worse?

    - by Josh Kelley
    As a longtime desktop developer looking at doing our first large-scale web application, what are the pros and cons of doing web development? Is developing a web application much worse than developing a desktop app? E.g., is it more tedious or annoying? Is the time to market much worse? Is the web platform excessively limiting? If the answer to any of these is yes, then why? (And how does developing a Flash or Silverlight app compare?)

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  • Is code maintenance typically a special project, or is it considered part of daily work?

    - by blueberryfields
    Earlier, I asked to find out which tools are commonly used to monitor methods and code bases, to find out whether the methods have been getting too long. Most of the responses there suggested that, beyond maintenance on the method currently being edited, programmers don't, in general, keep an eye on the rest of the code base. So I thought I'd ask the question in general: Is code maintenance, in general, considered part of your daily work? Do you find that you're spending at least some of your time cleaning up, refactoring, rewriting code in the code base, to improve it, as part of your other assigned work? Is it expected of you/do you expect it of your teammates? Or is it more common to find that cleanup, refactoring, and general maintenance on the codebase as a whole, occurs in bursts (for example, mostly as part of code reviews, or as part of refactoring/cleaning up projects)?

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  • Business/Development Liaison Wanting To Enhance Understanding In Programming

    - by James Alexander
    I lead software development for a team of of about 20 devs and we're primarily a .net/sql server shop. We've recently created a new role in our organization for a more business like role to assist in prioritization of development and this business liaison has asked me if there are any books or resources he could use to better understand software concepts in a meaningful way. Any suggestions or advice would be greatly appreciated.

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  • Going into Web Development without a C.S. Degree - Suggestions

    - by Klaint Cokeman
    I plan on seeking a career in web development and I'm about two semesters away from graduating with a CIS degree. Although I'm very satisfied with my choice of degree, I'm concerned that I may be lacking knowledge in a few areas because of not majoring in computer science. The programming side of things is no problem for me, I'm just wondering to what extent data structures/theory/etc. might benefit me to learn over spending more time with hands-on programming... and also what aspects of C.S. would be most appropriate to look into you would think would be most applicable to web development. In short, I'd like to expand my horizons a little bit. I'd very much appreciate and advice/suggestions/book or tutorial recommendations, etc. Thanks.

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  • Web development starting a career [closed]

    - by user985482
    Hi I am in the 3rd and last year at college of informatics and I am interested to follow a career in web development when I finish(2 more months). From what I understand this days to get hired you need to be able to know a variety of technologies at least that is the case in Romania.Most of the jobs I have seen even at entry level asks you to know the following: HTML/CSS Javascript , a framework preferable jQuery , Ajax a server side language in my case PHP and a framework SQL and an RDBMS in my case MySql a CMS in my case Wordpress My question is how well should me or anyone looking to get hired as a web developer for there first job should we know this technologies in order to get hired and what else should we aim to learn to have a better chance of getting hired. I don't know if the question is right for this forum but I believe that this could help many of the students and anyone who is taking an interest in web development to know what they should expect from there employers when they try to find work.

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  • Hyperlinked, externalized source code documentation

    - by Dave Jarvis
    Why do we still embed natural language descriptions of source code (i.e., the reason why a line of code was written) within the source code, rather than as a separate document? Given the expansive real-estate afforded to modern development environments (high-resolution monitors, dual-monitors, etc.), an IDE could provide semi-lock-step panels wherein source code is visually separated from -- but intrinsically linked to -- its corresponding comments. For example, developers could write source code comments in a hyper-linked markup language (linking to additional software requirements), which would simultaneously prevent documentation from cluttering the source code. What shortcomings would inhibit such a software development mechanism? A mock-up to help clarify the question: When the cursor is at a particular line in the source code (shown with a blue background, above), the documentation that corresponds to the line at the cursor is highlighted (i.e., distinguished from the other details). As noted in the question, the documentation would stay in lock-step with the source code as the cursor jumps through the source code. A hot-key could switch between "documentation mode" and "development mode". Potential advantages include: More source code and more documentation on the screen(s) at once Ability to edit documentation independently of source code (regardless of language?) Write documentation and source code in parallel without merge conflicts Real-time hyperlinked documentation with superior text formatting Quasi-real-time machine translation into different natural languages Every line of code can be clearly linked to a task, business requirement, etc. Documentation could automatically timestamp when each line of code was written (metrics) Dynamic inclusion of architecture diagrams, images to explain relations, etc. Single-source documentation (e.g., tag code snippets for user manual inclusion). Note: The documentation window can be collapsed Workflow for viewing or comparing source files would not be affected How the implementation happens is a detail; the documentation could be: kept at the end of the source file; split into two files by convention (filename.c, filename.c.doc); or fully database-driven By hyperlinked documentation, I mean linking to external sources (such as StackOverflow or Wikipedia) and internal documents (i.e., a wiki on a subdomain that could cross-reference business requirements documentation) and other source files (similar to JavaDocs). Related thread: What's with the aversion to documentation in the industry?

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  • Copyrights concerning code snippets and larger amounts of code

    - by JustcallmeDrago
    I am designing a public code repository. Users will be allowed to post and edit whatever amount of code they want, from code snippets to entire multi-file projects. I have a few major legal concerns about this: Not getting sued/shut down - I feel the site would be a much easier target than tracking down an individual user to sue. I have looked around a bit and see links to legal info in the footer of each page is common. What specific things should I do--and what does does a site such as YouTube (which I see copyrighted material on all the time) do--for protection? Citing sources and editing sourced code - If a user wants to post code that isn't theirs, what concerns/safeguards should I have? Will a link suffice, and what do I need further to allow the code to be edited (to improve it for example)? What can happen if a user posts copyrighted code without citing it? Large chunks of code - What legal differences should I look out for as the amount grows? Not having a mess of licenses for the site - I would like to have a single license (like RosettaCode) that keeps things simple for interaction on the site. I want the code to be postable and editable. I have looked into StackOverflow's CreativeCommons license a little and it says that If you alter, transform, or build upon this work, you may distribute the resulting work only under the same or similar license to this one. And on RosettaCode: All software found on Rosetta Code should be considered potentially hazardous. Use at your own risk. Be aware that all code on Rosetta Code is under the GNU Free Documentation License, as are any edits made by contributors. See Rosetta Code:Copyrights for details. What other licenses are like this? Commercializing the site - In what ways can I and can't I make money off of a site that contains code like this? All code will be publicly visible. Initial thoughts are having ads or making money by charging for advanced features.

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  • Design by Contract with Microsoft .Net Code Contract

    - by Fredrik N
    I have done some talks on different events and summits about Defensive Programming and Design by Contract, last time was at Cornerstone’s Developer Summit 2010. Next time will be at SweNug (Sweden .Net User Group). I decided to write a blog post about of some stuffs I was talking about. Users are a terrible thing! Protect your self from them ”Human users have a gift for doing the worst possible thing at the worst possible time.” – Michael T. Nygard, Release It! The kind of users Michael T. Nygard are talking about is the users of a system. We also have users that uses our code, the users I’m going to focus on is the users of our code. Me and you and another developers. “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” – Martin Fowler Good programmers also writes code that humans know how to use, good programmers also make sure software behave in a predictable manner despise inputs or user actions. Design by Contract   Design by Contract (DbC) is a way for us to make a contract between us (the code writer) and the users of our code. It’s about “If you give me this, I promise to give you this”. It’s not about business validations, that is something completely different that should be part of the domain model. DbC is to make sure the users of our code uses it in a correct way, and that we can rely on the contract and write code in a way where we know that the users will follow the contract. It will make it much easier for us to write code with a contract specified. Something like the following code is something we may see often: public void DoSomething(Object value) { value.DoIKnowThatICanDoThis(); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Where “value” can be uses directly or passed to other methods and later be used. What some of us can easily forget here is that the “value” can be “null”. We will probably not passing a null value, but someone else that uses our code maybe will do it. I think most of you (including me) have passed “null” into a method because you don’t know if the argument need to be specified to a valid value etc. I bet most of you also have got the “Null reference exception”. Sometimes this “Null reference exception” can be hard and take time to fix, because we need to search among our code to see where the “null” value was passed in etc. Wouldn’t it be much better if we can as early as possible specify that the value can’t not be null, so the users of our code also know it when the users starts to use our code, and before run time execution of the code? This is where DbC comes into the picture. We can use DbC to specify what we need, and by doing so we can rely on the contract when we write our code. So the code above can actually use the DoIKnowThatICanDoThis() method on the value object without being worried that the “value” can be null. The contract between the users of the code and us writing the code, says that the “value” can’t be null.   Pre- and Postconditions   When working with DbC we are specifying pre- and postconditions.  Precondition is a condition that should be met before a query or command is executed. An example of a precondition is: “The Value argument of the method can’t be null”, and we make sure the “value” isn’t null before the method is called. Postcondition is a condition that should be met when a command or query is completed, a postcondition will make sure the result is correct. An example of a postconditon is “The method will return a list with at least 1 item”. Commands an Quires When using DbC, we need to know what a Command and a Query is, because some principles that can be good to follow are based on commands and queries. A Command is something that will not return anything, like the SQL’s CREATE, UPDATE and DELETE. There are two kinds of Commands when using DbC, the Creation commands (for example a Constructor), and Others. Others can for example be a Command to add a value to a list, remove or update a value etc. //Creation commands public Stack(int size) //Other commands public void Push(object value); public void Remove(); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   A Query, is something that will return something, for example an Attribute, Property or a Function, like the SQL’s SELECT.   There are two kinds of Queries, the Basic Queries  (Quires that aren’t based on another queries), and the Derived Queries, queries that is based on another queries. Here is an example of queries of a Stack: //Basic Queries public int Count; public object this[int index] { get; } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To understand about some principles that are good to follow when using DbC, we need to know about the Commands and different Queries. The 6 Principles When working with DbC, it’s advisable to follow some principles to make it easier to define and use contracts. The following DbC principles are: Separate commands and queries. Separate basic queries from derived queries. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries. For each command, write a postcondition that specifies the value of every basic query. For every query and command, decide on a suitable precondition. Write invariants to define unchanging properties of objects. Before I will write about each of them I want you to now that I’m going to use .Net 4.0 Code Contract. I will in the rest of the post uses a simple Stack (Yes I know, .Net already have a Stack class) to give you the basic understanding about using DbC. A Stack is a data structure where the first item in, will be the first item out. Here is a basic implementation of a Stack where not contract is specified yet: public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } //Is related to Count and this[] Query public object Top() { return this[Count]; } //Creation commands public Stack(uint size) { Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { this[++Count] = value; } public void Remove() { this[Count] = null; Count--; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The Stack is implemented in a way to demonstrate the use of Code Contract in a simple way, the implementation may not look like how you would implement it, so don’t think this is the perfect Stack implementation, only used for demonstration.   Before I will go deeper into the principles I will simply mention how we can use the .Net Code Contract. I mention before about pre- and postcondition, is about “Require” something and to “Ensure” something. When using Code Contract, we will use a static class called “Contract” and is located in he “System.Diagnostics.Contracts” namespace. The contract must be specified at the top or our member statement block. To specify a precondition with Code Contract we uses the Contract.Requires method, and to specify a postcondition, we uses the Contract.Ensure method. Here is an example where both a pre- and postcondition are used: public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The contract above requires that the Count is greater than 0, if not we can’t get the item at the Top of a Stack. We also Ensures that the results (By using the Contract.Result method, we can specify a postcondition that will check if the value returned from a method is correct) of the Top query is equal to this[Count].   1. Separate Commands and Queries   When working with DbC, it’s important to separate Command and Quires. A method should either be a command that performs an Action, or returning information to the caller, not both. By asking a question the answer shouldn’t be changed. The following is an example of a Command and a Query of a Stack: public void Push(object value) public object Top() .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   The Push is a command and will not return anything, just add a value to the Stack, the Top is a query to get the item at the top of the stack.   2. Separate basic queries from derived queries There are two different kinds of queries,  the basic queries that doesn’t rely on another queries, and derived queries that uses a basic query. The “Separate basic queries from derived queries” principle is about about that derived queries can be specified in terms of basic queries. So this principles is more about recognizing that a query is a derived query or a basic query. It will then make is much easier to follow the other principles. The following code shows a basic query and a derived query: //Basic Queries public uint Count; //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   We can see that IsEmpty will use the Count query, and that makes the IsEmpty a Derived query.   3. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries.   When the derived query is recognize we can follow the 3ed principle. For each derived query, we can create a postcondition that specifies what result our derived query will return in terms of one or more basic queries. Remember that DbC is about contracts between the users of the code and us writing the code. So we can’t use demand that the users will pass in a valid value, we must also ensure that we will give the users what the users wants, when the user is following our contract. The IsEmpty query of the Stack will use a Count query and that will make the IsEmpty a Derived query, so we should now write a postcondition that specified what results will be returned, in terms of using a basic query and in this case the Count query, //Basic Queries public uint Count; //Derived Queries public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } The Contract.Ensures is used to create a postcondition. The above code will make sure that the results of the IsEmpty (by using the Contract.Result to get the result of the IsEmpty method) is correct, that will say that the IsEmpty will be either true or false based on Count is equal to 0 or not. The postcondition are using a basic query, so the IsEmpty is now following the 3ed principle. We also have another Derived Query, the Top query, it will also need a postcondition and it uses all basic queries. The Result of the Top method must be the same value as the this[] query returns. //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count and this[] Query public object Top() { Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   4. For each command, write a postcondition that specifies the value of every basic query.   For each command we will create a postconditon that specifies the value of basic queries. If we look at the Stack implementation we will have three Commands, one Creation command, the Constructor, and two others commands, Push and Remove. Those commands need a postcondition and they should include basic query to follow the 4th principle. //Creation commands public Stack(uint size) { Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   As you can see the Create command will Ensures that Count will be 0 when the Stack is created, when a Stack is created there shouldn’t be any items in the stack. The Push command will take a value and put it into the Stack, when an item is pushed into the Stack, the Count need to be increased to know the number of items added to the Stack, and we must also make sure the item is really added to the Stack. The postconditon of the Push method will make sure the that old value of the Count (by using the Contract.OldValue we can get the value a Query has before the method is called)  plus 1 will be equal to the Count query, this is the way we can ensure that the Push will increase the Count with one. We also make sure the this[] query will now contain the item we pushed into the Stack. The Remove method must make sure the Count is decreased by one when the top item is removed from the Stack. The Commands is now following the 4th principle, where each command now have a postcondition that used the value of basic queries. Note: The principle says every basic Query, the Remove only used one Query the Count, it’s because this command can’t use the this[] query because an item is removed, so the only way to make sure an item is removed is to just use the Count query, so the Remove will still follow the principle.   5. For every query and command, decide on a suitable precondition.   We have now focused only on postcondition, now time for some preconditons. The 5th principle is about deciding a suitable preconditon for every query and command. If we starts to look at one of our basic queries (will not go through all Queries and commands here, just some of them) the this[] query, we can’t pass an index that is lower then 1 (.Net arrays and list are zero based, but not the stack in this blog post ;)) and the index can’t be lesser than the number of items in the stack. So here we will need a preconditon. public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Think about the Contract as an documentation about how to use the code in a correct way, so if the contract could be specified elsewhere (not part of the method body), we could simply write “return _array[index]” and there is no need to check if index is greater or lesser than Count, because that is specified in a “contract”. The implementation of Code Contract, requires that the contract is specified in the code. As a developer I would rather have this contract elsewhere (Like Spec#) or implemented in a way Eiffel uses it as part of the language. Now when we have looked at one Query, we can also look at one command, the Remove command (You can see the whole implementation of the Stack at the end of this blog post, where precondition is added to more queries and commands then what I’m going to show in this section). We can only Remove an item if the Count is greater than 0. So we can write a precondition that will require that Count must be greater than 0. public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   6. Write invariants to define unchanging properties of objects.   The last principle is about making sure the object are feeling great! This is done by using invariants. When using Code Contract we can specify invariants by adding a method with the attribute ContractInvariantMethod, the method must be private or public and can only contains calls to Contract.Invariant. To make sure the Stack feels great, the Stack must have 0 or more items, the Count can’t never be a negative value to make sure each command and queries can be used of the Stack. Here is our invariant for the Stack object: [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   Note: The ObjectInvariant method will be called every time after a Query or Commands is called. Here is the full example using Code Contract:   public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } set { Contract.Requires(index >= 1); Contract.Requires(index <= Count); _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } //Is related to Count and this[] Query public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } //Creation commands public Stack(uint size) { Contract.Requires(size > 0); Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Requires(value != null); Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Summary By using Design By Contract we can make sure the users are using our code in a correct way, and we must also make sure the users will get the expected results when they uses our code. This can be done by specifying contracts. To make it easy to use Design By Contract, some principles may be good to follow like the separation of commands an queries. With .Net 4.0 we can use the Code Contract feature to specify contracts.

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  • Recommendation for a platform to teach game development to kids [closed]

    - by Moshe Kravchik
    My 11 years old son decided he want to create a Web game. He does not know much about programming and I never did any game development so I'm not the best teacher of the topic. On one hand I really want him to get into building things and doing his own game sounds perfect. So I'd like to find a way to keep him interested and progressing by himself. This means that I'm looking for a platform that is: 1. Simple for understanding and use, intuitive interface 2. Powerful 3. Good tools, preferrably free 4. Significant community for questions and tips 5. Localization - my son's English is quite poor (native Hebrew). We looked at Alice, but it was too limited in its abilities and isn't really a Web game building platform. HTML/CSS and Javascript - too low level for a kid to keep the interest. What would you recommend?

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  • Development processes, the use of version control, and unit-testing

    - by ct01
    Preface I've worked at quite a few "flat" organizations in my time. Most of the version control policy/process has been "only commit after it's been tested". We were constantly committing at each place to "trunk" (cvs/svn). The same was true with unit-testing - it's always been a "we need to do this" mentality but it never really materializes in a substantive form b/c there is no institutional knowledge base to do it - no mentorship. Version Control The emphasis for version control management at one place was a very strict protocol for commit messages (format & content). The other places let employees just do "whatever". The branching, tagging, committing, rolling back, and merging aspect of things was always ill defined and almost never used. This sort of seems to leave the version control system in the position of being a fancy file-storage mechanism with a meta-data component that never really gets accessed/utilized. (The same was true for unit testing and committing code to the source tree) Unit tests It seems there's a prevailing "we must/should do this" mentality in most places I've worked. As a policy or standard operating procedure it never gets implemented because there seems to be a very ill-defined understanding about what that means, what is going to be tested, and how to do it. Summary It seems most places I've been to think version control and unit testing is "important" b/c the trendy trade journals say it is but, if there's very little mentorship to use these tools or any real business policies, then the full power of version control/unit testing is never really expressed. So grunts, like myself, never really have a complete understanding of the point beyond that "it's a good thing" and "we should do it". Question I was wondering if there are blogs, books, white-papers, or online journals about what one could call the business process or "standard operating procedures" or uses cases for version control and unit testing? I want to know more than the trade journals tell me and get serious about doing these things. PS: @Henrik Hansen had a great comment about the lack of definition for the question. I'm not interested in a specific unit-testing/versioning product or methodology (like, XP) - my interest is more about work-flow at the individual team/developer level than evangelism. This is more-or-less a by product of the management situation I've operated under more than a lack of reading software engineering books or magazines about development processes. A lot of what I've seen/read is more marketing oriented material than any specifically enumerated description of "well, this is how our shop operates".

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  • Can notes/to-dos in code comments sent to code-reviews result in an effective refactoring process?

    - by dukeofgaming
    I want to start/improve a culture of collective code ownership at my company but at a geographically distributed level... I'd say there is some current collective code-ownership mentality, but only at single geographical sites. This is a follow-up to this question: What is the politically correct way of refactoring other's code? I'm just wondering if submitting *just code comments* for code reviews (we have ReviewBoard, possibly upgrading to Crucible) could actually be an effective mechanism to get the conversation started on improving code, without having others feel territorial about their code. For example, if I add: //ToDo: Refactor this code and that code because of reasons X and Y Then, submit it for code review, and it gets accepted... it could be considered as an agreement (which I think is sometimes harder to get with new code up front). At the same time, the author (and others) might have an easier time digesting and accepting the proposal; rejecting a proposal because it might break things will not longer be a valid reason and therefore the fear of making a change is lost... and at the same time, do not invest 10 hours optimizing something that no one thinks it is worth it and opposes to it just out of fear. This is all conjecture, but I'm feeling something like this (submitting refactoring notes in code comments at the code-review process) would work. Has anyone done something like this in practice?, if so, what have been the results?

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  • Technical development decision for my newly established software company

    - by test test
    I have a new software company where I am planning to develop CRM system. So I have settled down on the technological approach I am going to use:- I will use an open source Java-based CRM engine. I will use a third party reporting tool named JasperReports for providing reports capabilities for the CRM. I will develop the interface and any customization which the customer might ask for using asp.net mvc framework since my knowledge and experience are based on asp.net. And I will use the CRM API to integrate my asp.net web application with the Java-based CRM. I have developed a simple demo which integrate these three main components (CRM engine, asp.net application and the reporting tool) and they worked well. But I am afraid of the following risk that I might face if I go with the above approach: I should hire developers with different skills and experience: Developers with Java skills to be able to modify the Java-based CRM and writing plug-ins -when needed- to extend the CRM capabilities. Other developers with asp.net skills to be able to build the application such as application forms, the portal from where users will be able to start the CRM processes, searching capabilities, etc. So might the above point raise some risks when I start hiring a new team and start building the CRM application, OR I am on the right track at this early stage?

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  • How to install and make development use of gtk+ on Ubuntu 12.04

    - by el10780
    I want to install gtk+ in order to make an application with a graphical environment.I went to the official website of gtk(gtk.org) and I tried to follow the instructions,but I wasn't able to make it work.I think that I have successfully managed to do the whole process till the part that I had to run make install and after that ldconfig.So far so good.After that though the complete chaos.I do not know how to set all these configurations so I can make my compilers know where to look for the include files.I just want to make it work in my Ubuntu when I start making a source file and then compile it and run it.

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