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  • Using LINQ Lambda Expressions to Design Customizable Generic Components

    LINQ makes code easier to write and maintain by abstracting the data source. It provides a uniform way to handle widely diverse data structures within an application. LINQ’s Lambda syntax is clever enough to even allow you to create generic building blocks with hooks, into which you can inject arbitrary functions. Michael Sorens explains, and demonstrates with examples. span.fullpost {display:none;}

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  • Using LINQ Lambda Expressions to Design Customizable Generic Components

    LINQ makes code easier to write and maintain by abstracting the data source. It provides a uniform way to handle widely diverse data structures within an application. LINQ’s Lambda syntax is clever enough even to allow you to create generic building blocks with hooks into which you can inject arbitrary functions. Michael Sorens explains, and demonstrates with examples.

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  • What are algorithmic paradigms?

    - by Vaibhav Agarwal
    We generally talk about paradigms of programming as functional, procedural, object oriented, imperative etc but what should I reply when I am asked the paradigms of algorithms? For example are Travelling Salesman Problem, Dijkstra Shortest Path Algorithm, Euclid GCD Algorithm, Binary search, Kruskal's Minimum Spanning Tree, Tower of Hanoi paradigms of algorithms? Should I answer the data structures I would use to design these algorithms?

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  • const vs. readonly for a singleton

    - by GlenH7
    First off, I understand there are folk who oppose the use of singletons. I think it's an appropriate use in this case as it's constant state information, but I'm open to differing opinions / solutions. (See The singleton pattern and When should the singleton pattern not be used?) Second, for a broader audience: C++/CLI has a similar keyword to readonly with initonly, so this isn't strictly a C# type question. (Literal field versus constant variable in C++/CLI) Sidenote: A discussion of some of the nuances on using const or readonly. My Question: I have a singleton that anchors together some different data structures. Part of what I expose through that singleton are some lists and other objects, which represent the necessary keys or columns in order to connect the linked data structures. I doubt that anyone would try to change these objects through a different module, but I want to explicitly protect them from that risk. So I'm currently using a "readonly" modifier on those objects*. I'm using readonly instead of const with the lists as I read that using const will embed those items in the referencing assemblies and will therefore trigger a rebuild of those referencing assemblies if / when the list(s) is/are modified. This seems like a tighter coupling than I would want between the modules, but I wonder if I'm obsessing over a moot point. (This is question #2 below) The alternative I see to using "readonly" is to make the variables private and then wrap them with a public get. I'm struggling to see the advantage of this approach as it seems like wrapper code that doesn't provide much additional benefit. (This is question #1 below) It's highly unlikely that we'll change the contents or format of the lists - they're a compilation of things to avoid using magic strings all over the place. Unfortunately, not all the code has converted over to using this singleton's presentation of those strings. Likewise, I don't know that we'd change the containers / classes for the lists. So while I normally argue for the encapsulations advantages a get wrapper provides, I'm just not feeling it in this case. A representative sample of my singleton public sealed class mySingl { private static volatile mySingl sngl; private static object lockObject = new Object(); public readonly Dictionary<string, string> myDict = new Dictionary<string, string>() { {"I", "index"}, {"D", "display"}, }; public enum parms { ABC = 10, DEF = 20, FGH = 30 }; public readonly List<parms> specParms = new List<parms>() { parms.ABC, parms.FGH }; public static mySingl Instance { get { if(sngl == null) { lock(lockObject) { if(sngl == null) sngl = new mySingl(); } } return sngl; } } private mySingl() { doSomething(); } } Questions: Am I taking the most reasonable approach in this case? Should I be worrying about const vs. readonly? is there a better way of providing this information?

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  • C++ Development Cinder/Visual Studio

    - by jayReegs
    I'm currently taking a Data Structures course that involves the development of C++ applications using microsoft visual studio express c++, an application called Cinder, and we turn in assignments via GitHub. I know Mac users in the class use X code to develop to our needs although some small issues arise with compilation that needs some debug work to be done. Windows just isn't cutting it for me anymore...I've welcomed myself to the darkside...I'm wondering if Linux distros have any development tools that would be compatible to create and run these types of applications?

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  • Columnstore Case Study #2: Columnstore faster than SSAS Cube at DevCon Security

    - by aspiringgeek
    Preamble This is the second in a series of posts documenting big wins encountered using columnstore indexes in SQL Server 2012 & 2014.  Many of these can be found in my big deck along with details such as internals, best practices, caveats, etc.  The purpose of sharing the case studies in this context is to provide an easy-to-consume quick-reference alternative. See also Columnstore Case Study #1: MSIT SONAR Aggregations Why Columnstore? As stated previously, If we’re looking for a subset of columns from one or a few rows, given the right indexes, SQL Server can do a superlative job of providing an answer. If we’re asking a question which by design needs to hit lots of rows—DW, reporting, aggregations, grouping, scans, etc., SQL Server has never had a good mechanism—until columnstore. Columnstore indexes were introduced in SQL Server 2012. However, they're still largely unknown. Some adoption blockers existed; yet columnstore was nonetheless a game changer for many apps.  In SQL Server 2014, potential blockers have been largely removed & they're going to profoundly change the way we interact with our data.  The purpose of this series is to share the performance benefits of columnstore & documenting columnstore is a compelling reason to upgrade to SQL Server 2014. The Customer DevCon Security provides home & business security services & has been in business for 135 years. I met DevCon personnel while speaking to the Utah County SQL User Group on 20 February 2012. (Thanks to TJ Belt (b|@tjaybelt) & Ben Miller (b|@DBADuck) for the invitation which serendipitously coincided with the height of ski season.) The App: DevCon Security Reporting: Optimized & Ad Hoc Queries DevCon users interrogate a SQL Server 2012 Analysis Services cube via SSRS. In addition, the SQL Server 2012 relational back end is the target of ad hoc queries; this DW back end is refreshed nightly during a brief maintenance window via conventional table partition switching. SSRS, SSAS, & MDX Conventional relational structures were unable to provide adequate performance for user interaction for the SSRS reports. An SSAS solution was implemented requiring personnel to ramp up technically, including learning enough MDX to satisfy requirements. Ad Hoc Queries Even though the fact table is relatively small—only 22 million rows & 33GB—the table was a typical DW table in terms of its width: 137 columns, any of which could be the target of ad hoc interrogation. As is common in DW reporting scenarios such as this, it is often nearly to optimize for such queries using conventional indexing. DevCon DBAs & developers attended PASS 2012 & were introduced to the marvels of columnstore in a session presented by Klaus Aschenbrenner (b|@Aschenbrenner) The Details Classic vs. columnstore before-&-after metrics are impressive. Scenario   Conventional Structures   Columnstore   Δ SSRS via SSAS 10 - 12 seconds 1 second >10x Ad Hoc 5-7 minutes (300 - 420 seconds) 1 - 2 seconds >100x Here are two charts characterizing this data graphically.  The first is a linear representation of Report Duration (in seconds) for Conventional Structures vs. Columnstore Indexes.  As is so often the case when we chart such significant deltas, the linear scale doesn’t expose some the dramatically improved values corresponding to the columnstore metrics.  Just to make it fair here’s the same data represented logarithmically; yet even here the values corresponding to 1 –2 seconds aren’t visible.  The Wins Performance: Even prior to columnstore implementation, at 10 - 12 seconds canned report performance against the SSAS cube was tolerable. Yet the 1 second performance afterward is clearly better. As significant as that is, imagine the user experience re: ad hoc interrogation. The difference between several minutes vs. one or two seconds is a game changer, literally changing the way users interact with their data—no mental context switching, no wondering when the results will appear, no preoccupation with the spinning mind-numbing hurry-up-&-wait indicators.  As we’ve commonly found elsewhere, columnstore indexes here provided performance improvements of one, two, or more orders of magnitude. Simplified Infrastructure: Because in this case a nonclustered columnstore index on a conventional DW table was faster than an Analysis Services cube, the entire SSAS infrastructure was rendered superfluous & was retired. PASS Rocks: Once again, the value of attending PASS is proven out. The trip to Charlotte combined with eager & enquiring minds let directly to this success story. Find out more about the next PASS Summit here, hosted this year in Seattle on November 4 - 7, 2014. DevCon BI Team Lead Nathan Allan provided this unsolicited feedback: “What we found was pretty awesome. It has been a game changer for us in terms of the flexibility we can offer people that would like to get to the data in different ways.” Summary For DW, reports, & other BI workloads, columnstore often provides significant performance enhancements relative to conventional indexing.  I have documented here, the second in a series of reports on columnstore implementations, results from DevCon Security, a live customer production app for which performance increased by factors of from 10x to 100x for all report queries, including canned queries as well as reducing time for results for ad hoc queries from 5 - 7 minutes to 1 - 2 seconds. As a result of columnstore performance, the customer retired their SSAS infrastructure. I invite you to consider leveraging columnstore in your own environment. Let me know if you have any questions.

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  • Two BULK INSERT issues I worked around recently

    - by AaronBertrand
    Since I am still afraid of SSIS, and because I am dealing mostly with CSV files and table structures that are relatively simple and require only one of the three letters in the acronym "ETL," I find myself using BULK INSERT a lot. I have been meaning to switch to using CLR, since I am doing a lot of file system querying using xp_cmdshell, but I haven't had the chance to really explore it yet. I know, a lot of you are probably thinking, wow, look at all those bad habits. But for every person thinking...(read more)

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  • Basic web architecture : Perl -> PHP

    - by Sunny Jim
    This is an architecture question. If there is a better forum, please redirect me. Apologies in advance. Essentially every website is built around a relational database, right? When a user uploads form data, that data is stored in a table. The problem is that the table structure(s) need to be modified whenever the website form is modified. Although I understand that modern web frameworks work around this problem by automatically building forms based on the table structure. For the last 20 years, I have been building websites using Perl. When I first encountered this problem, the easiest solution was to save serialized Perl objects as data BLOBS. After XML's introduction, this solution worked even better because XML is so effective for representing arbitrary data. This approach is consistent with the original Perl principles of Hubris, Laziness, and Impatience and I'm pretty committed to it. Obviously, the biggest drawback is that this solution locks me into the Perl interpreter. So instead, I've just completed a prototype of a universal RDB table. The prototype is written in Perl but porting it to PHP will be a good chance to develop those skills. The principal is based on the XML::Dumper module, which converts arbitrary Perl data structures into uniform XML. With my approach, each XML node is stored as a table record. I underestimated this undertaking and rolled something up myself. But the effort allows me to discuss the basic design instead of implementation details. As mentioned, I'm pretty committed to this approach of using flexible data structures. It's been successfully deployed on many websites, large, and complex. But are there any drawbacks I've overlooked? I rolled my own. Are other people taking a similar approach to their data? What kinds of solutions are available? I have not abandoned my dream of eventually contributing something useful to the worldwide community. In order to proceed, the next step would be peer review. How does one pursue that effort? Thanks! -Jim

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  • Développer des fonctions scalaires (UDF) avec PLpgSQL, par SQLpro

    Bonjour, voici le premier d'une nouvelle série d'articles consacrés au développement des fonctions sous PLpgSQL Ce premier article est consacré aux fonctions scalaires appelées dans la norme SQL "UDF" pour User Defined Function Il sera suivi dans les mois prochains de deux autres articles : l'un sur les fonctions de manipulation des tables et l'autre sur les fonctions Sommaire : 0 - INTRODUCTION 1 - CRÉATION D'UNE FONCTION SCALAIRE 2 - UTILISATION DE LA FONCTION 3 - FONCTION AVEC LANGAGE SQL 4 - QUELQUES MOTS CLEFS DE PL/pgSQL 5 - ARGUMENTS 6 - VARIABLES ET CONSTANTES 7 - POLYMORPHISME 8 - STRUCTURES DE TEST ET BRANCHEMENTS 9 - GESTION D'ERRE...

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  • Two BULK INSERT issues I worked around recently

    - by AaronBertrand
    Since I am still afraid of SSIS, and because I am dealing mostly with CSV files and table structures that are relatively simple and require only one of the three letters in the acronym "ETL," I find myself using BULK INSERT a lot. I have been meaning to switch to using CLR, since I am doing a lot of file system querying using xp_cmdshell, but I haven't had the chance to really explore it yet. I know, a lot of you are probably thinking, wow, look at all those bad habits. But for every person thinking...(read more)

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  • Help needed on a UI/Developer Interview

    - by AJ Seth
    I have a phone interview with a major Internet company and it is a mostly front-end developer position. If anyone has experience with UI/developer interviews and can give some advice/questions asked etc. that'll be great. Additionally, what resources can be read and reviewed for the following: Designing for performance, scalability and availability Internet and OS security fundamentals EDIT: Now I am told that the interview I am told will be mostly on coding, Data Structures, design questions etc. Anyone?

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  • C++ track or Java track in college?

    - by sq1020
    I'm starting some CS classes at a community college and they have two tracks. Either you take three courses in C++ or three courses in Java. Both cover the same fundamental material e.g. data structures, algorithms etc. Which would you recommend considering that I know python and may be consider doing a masters in CS some time down the road....my undergrad degree is in something else. And advice would be appreciated.

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  • Creating an interactive grid for a puzzle game

    - by Noupoi
    I am trying to make a slitherlink game, and am not too sure how to approach creating the game, more specifically the grid structure on which the puzzle will be played on. This is what a empty and completed slitherlink grid would look like: The numbers in the squares are sort of clues and the areas between the dots need to be clickable: I would like to create the game in VB .NET. What data structures should I try to use, and would it be beneficial using any frameworks such as XNA?

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  • Power Distribution amongst connected nodes

    - by Perky
    In my game the map is represented by connected nodes, each node has a number of connected nodes. The nodes represent a system in which players can build structures and move units about. If you're familiar with Sins of a Solar Empire the game map is very similar. I want each node to be able to produce power and share it with all connected nodes. For example if A, B, C & D are all connected and produce 100 power units, then each system should have 400 power units available. If node B builds a structure that consumes 100 power units then A, B, C & D should then have 300 power units available. I've been working on this system all day and haven't been able to get it working quite the way I want. My current implementation is to first recurse through each nodes's connected node adding up the power, I keep a list of closed nodes so it doesn't loop, it's quite similar to A* actually. Pseudo code: All nodes start with the properties node.power = 0 node.basePower = 100 // could be different for each node. node.initialPower = node.basePower - function propagatePower( node, initialPower, closedNodes ) node.power += initialPower add( closedNodes, node ) connectedNodes = connected_nodes_except_from( closedNodes ) foreach node in connectedNodes do propagatePower( node, initialPower, closedNodes ) end end After this I iterate through all power consumers. foreach consumer in consumers do node = consumer.parentNode if node.power >= consumer.powerConsumption then consumer.powerConsumed += consumer.powerConsumption node.producedPower -= consumer.powerConsumption end end Then I adjust the initial power for the next propagation cycle. foreach node in nodes do node.initialPower = node.basePower - node.producedPower node.displayPower = node.power // for rendering the power. node.power = 0 end This seemed to work at first but then I came into a problem. Say two nodes A & B produce 100Pu each, it's shared so both A & B have 200Pu. I then make two structures that consume 80Pu each on A (160Pu). Then the nodes power is adjusted to basePower - producedPower (100-160 = -60). Nodes are propagated, both nodes now have 40Pu (A: -60 + B: 100 = 40). Which is correct because they started with 200Pu - 160Pu = 40Pu. However now node.power >= consumer.powerConsumption is false. Whats worse is it's false for any structure that uses more that 40Pu, so the whole system goes down. I could deduct from consumer.powerConsumption but what do I do if power is reduced elsewhere? I don't have the correct data to perform the necessary checks. It's late so I'm probably not thinking straight but I thought to ask on here to see if anyone has any other implementations, better or worse I'd be interested to know.

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  • Dealing with coworkers when developing, need advice [closed]

    - by Yippie-Kai-Yay
    I developed our current project architecture and started developing it on my own (reaching something like, revision 40). We're developing a simple subway routing framework and my design seemed to be done extremely well - several main models, corresponding views, main logic and data structures were modeled "as they should be" and fully separated from rendering, algorithmic part was also implemented apart from the main models and had a minor number of intersection points. I would call that design scalable, customizable, easy-to-implement, interacting mostly based on the "black box interaction" and, well, very nice. Now, what was done: I started some implementations of the corresponding interfaces, ported some convenient libraries and wrote implementation stubs for some application parts. I had the document describing coding style and examples of that coding style usage (my own written code). I forced the usage of more or less modern C++ development techniques, including no-delete code (wrapped via smart pointers) and etc. I documented the purpose of concrete interface implementations and how they should be used. Unit tests (mostly, integration tests, because there wasn't a lot of "actual" code) and a set of mocks for all the core abstractions. I was absent for 12 days. What do we have now (the project was developed by 4 other members of the team): 3 different coding styles all over the project (I guess, two of them agreed to use the same style :), same applies to the naming of our abstractions (e.g CommonPathData.h, SubwaySchemeStructures.h), which are basically headers declaring some data structures. Absolute lack of documentation for the recently implemented parts. What I could recently call a single-purpose-abstraction now handles at least 2 different types of events, has tight coupling with other parts and so on. Half of the used interfaces now contain member variables (sic!). Raw pointer usage almost everywhere. Unit tests disabled, because "(Rev.57) They are unnecessary for this project". ... (that's probably not everything). Commit history shows that my design was interpreted as an overkill and people started combining it with personal bicycles and reimplemented wheels and then had problems integrating code chunks. Now - the project still does only a small amount of what it has to do, we have severe integration problems, I assume some memory leaks. Is there anything possible to do in this case? I do realize that all my efforts didn't have any benefit, but the deadline is pretty soon and we have to do something. Did someone have a similar situation? Basically I thought that a good (well, I did everything that I could) start for the project would probably lead to something nice, however, I understand that I'm wrong. Any advice would be appreciated, sorry for my bad english.

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  • Are proofs worth the effort?

    - by Shashank Jain
    I bought the de-facto book for learning about data structures and algorithms (CLRS). The book is though quite good but the singularity is in the proofs. The book is filled with Lemmas, theorems, peculiar symbols and unimaginable recurrence relations which are very hard to understand. I am able to somehow get the algorithms but the discrete mathematics just not for me. So should I leave them out and just concentrate on algorithims?

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  • Speaking this week at Richmond SQL Server User Group

    - by drsql
    Thursday night, at 6:00 (or so) I will be speaking in Richmond ( http://richmondsql.org/cs2007/ ), talking about How to Implement a Hierarchy using SQL Server. The abstract is: One of the most common structures you will come across in the real world is a hierarchy (either a single parent "tree" or a multi-parent "graph"). Many systems will implement the obvious examples, such as a corporate managerial structure or a bill of materials. It turns out that almost any many-to-many relationship can be...(read more)

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  • Utiliser QML et QtWebKit avec PySide, le binding Python de Qt, un article traduit par Thibaut Cuvelier

    Ce tutoriel sur PySide montre comment intégrer du code Python et QtWebKit avec QML. Le résultat sera un contenu HTML et une logique dans une application QML, tout en pouvant envoyer des messages entre le contexte JavaScript de la QWebView et le monde Python. Il utilisera JSON, alert() et evaluateJavaScript() pour échanger des structures de données arbitraires (valeurs, listes, dictionnaires) entre Python et JavaScript dans la QWebView. Utiliser QML et QtWebKit avec PySide...

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  • Les Collections en Objective-C : Manipuler les tableaux, introduction à NSArray et NSMutableArray par Sylvain Gamel

    Retrouvez un nouvel article d'introduction aux tableaux d'objets : NSArray et à NSMutableArray. Citation: Les tableaux d'objets sont une structure de données courante et très souvent utilisées. Qu'est-ce qu'un tableau ? Un tableau est une liste ordonnée d'objets où chaque objet peut être accédé par sa position dans le tableau : son index. Java et Cocoa proposent évidemment des classes pour mettre en oeuvre ces structures de données. Cet article se propose d'introduire rapidement les principales fonctionnalités offe...

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  • Are non Turing-complete languages considered programming languages at all?

    - by user1598390
    Reading a recent question: Is it actually possible to have a 'useful' programming language that isn't Turing complete?, I've come to wonder if non Turing-complete programming languages are considered programming languages at all. Since Turing-completeness means a language has to have variables to store values as well as control structures ( for, while )... Is a language that lacks these features considered a programming language ?

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  • I want to learn to program in SDL C++where do i start? I want to learn only what i need to to start making 2d games [on hold]

    - by user2644399
    Lazyfoo of Lazyfoo.net of the SDL 2d tutorial wrote that in order for me to start game programming in SDL, I need to know these concepts well; Operators, Controls, Loops, Functions, Structures, Arrays, References, Pointers, Classes, Objects how to use a template and Bitwise and/or. I want to know the fastest way to learn as much as I need of basic c++ that would allow me to make 2d games. Thanks in advance.

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  • VoIP Phone Services: Things You must Know

    Moving along with the trend will not give you the desired profits automatically just for the reason that every organization has its own set of structures and requirements. Below Listed are a few basi... [Author: Dennis Smith - Computers and Internet - March 25, 2010]

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  • Temporary Object Caching Explained

    - by Paul White
    SQL Server 2005 onward caches temporary tables and table variables referenced in stored procedures for reuse, reducing contention on tempdb allocation structures and catalogue tables.  A number of things can prevent this caching (none of which are allowed when working with table variables): Named constraints (bad idea anyway, since concurrent executions can cause a name collision) DDL after creation (though what is considered DDL is interesting) Creation using dynamic SQL Table created in a...(read more)

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  • Organizing single page code well with Notepad++

    - by Hudson
    I've a c# file that will contain, most likely 10,000+ lines of code. I'd like to break this file into tabbed segments, so I can organize each method into a certain tab and label the tab something like : initial setup, helper functions,execution logic,list structures,global variables, etc. If I were using PHP I would have separate files and use include(); to include the separate files. What can be done, following the same style, with c#?

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  • Where to after a year of java? [closed]

    - by avatarX
    I've just finished a my first year of programming Java at varsity and I have a three month break. In terms of my development would it be better to: Cover Java in more depth to acquire a more intermediate level of ability Learn a new programming language (if so which) to a similar level as my current Java ability Spend timing learning introductory discrete maths, algorithms and data structures I'm also open to any other possibilities that would be beneficial but that could be covered in about 3 months.

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