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  • Database Functional Programming in Clojure

    - by Ralph
    "It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail." - Abraham Maslow I need to write a tool to dump a large hierarchical (SQL) database to XML. The hierarchy consists of a Person table with subsidiary Address, Phone, etc. tables. I have to dump thousands of rows, so I would like to do so incrementally and not keep the whole XML file in memory. I would like to isolate non-pure function code to a small portion of the application. I am thinking that this might be a good opportunity to explore FP and concurrency in Clojure. I can also show the benefits of immutable data and multi-core utilization to my skeptical co-workers. I'm not sure how the overall architecture of the application should be. I am thinking that I can use an impure function to retrieve the database rows and return a lazy sequence that can then be processed by a pure function that returns an XML fragment. For each Person row, I can create a Future and have several processed in parallel (the output order does not matter). As each Person is processed, the task will retrieve the appropriate rows from the Address, Phone, etc. tables and generate the nested XML. I can use a a generic function to process most of the tables, relying on database meta-data to get the column information, with special functions for the few tables that need custom processing. These functions could be listed in a map(table name -> function). Am I going about this in the right way? I can easily fall back to doing it in OO using Java, but that would be no fun. BTW, are there any good books on FP patterns or architecture? I have several good books on Clojure, Scala, and F#, but although each covers the language well, none look at the "big picture" of function programming design.

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  • Does immutability entirely eliminate the need for locks in multi-processor programming?

    - by GlenPeterson
    Part 1 Clearly Immutability minimizes the need for locks in multi-processor programming, but does it eliminate that need, or are there instances where immutability alone is not enough? It seems to me that you can only defer processing and encapsulate state so long before most programs have to actually DO something. If a program performs actions on multiple processors, something needs to collect and aggregate the results. All this involves multi-process communication before, after, and possibly during some transformations. The start and end state of the machines are different. Can this always be done with no locks just by throwing out each object and creating a new one instead of changing the original (a crude view of immutability)? What cases still require locking? I'm interested in both the theoretical/academic answer and the practical/real-world answer. I know a lot of functional programmers like to talk about "no side effect" but in the "real world" everything has a side effect. Every processor click takes time and electricity and machine resources away from other processes. So I understand that there may be more than one perspective to answer this question from. If immutability is safe, given certain bounds or assumptions, I want to know what the borders of the "safety zone" are exactly. Some examples of possible boundaries: I/O Exceptions/errors Interfaces with programs written in other languages Interfaces with other machines (physical, virtual, or theoretical) Special thanks to @JimmaHoffa for his comment which started this question! Part 2 Multi-processor programming is often used as an optimization technique - to make some code run faster. When is it faster to use locks vs. immutable objects? Given the limits set out in Amdahl's Law, when can you achieve better over-all performance (with or without the garbage collector taken into account) with immutable objects vs. locking mutable ones? Summary I'm combining these two questions into one to try to get at where the bounding box is for Immutability as a solution to threading problems.

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  • Function-Local Static Const variable Initialization semantics.

    - by Hassan Syed
    The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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  • Which language and platform features really boosted your coding speed?

    - by Serge
    The question is about delivering working code faster without any regard for design, quality, maintainability, etc. Here is the list of things that help me to write and read code faster: Language: static typing, support for object-oriented and functional programming styles, embedded documentation, short compile-debug-fix cycle or REPL, automatic memory management Platform: "batteries" included (text, regex, IO, threading, networking), thriving community, tons of open-source libs Tools: IDE, visual debugger, code-completion, code navigation, refactoring

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  • Microsoft .NET Web Programming: Web Sites versus Web Applications

    - by SAMIR BHOGAYTA
    In .NET 2.0, Microsoft introduced the Web Site. This was the default way to create a web Project in Visual Studio 2005. In Visual Studio 2008, the Web Application has been restored as the default web Project in Visual Studio/.NET 3.x The Web Site is a file/folder based Project structure. It is designed such that pages are not compiled until they are requested ("on demand"). The advantages to the Web Site are: 1) It is designed to accommodate non-.NET Applications 2) Deployment is as simple as copying files to the target server 3) Any portion of the Web Site can be updated without requiring recompilation of the entire Site. The Web Application is a .dll-based Project structure. ASP.NET pages and supporting files are compiled into assemblies that are then deployed to the target server. Advantages of the Web Application are: 1) Precompiled files do not expose code to an attacker 2) Precompiled files run faster because they are binary data (the Microsoft Intermediate Language, or MSIL) executed by the CLR (Common Language Runtime) 3) References, assemblies, and other project dependencies are built in to the compiled site and automatically managed. They do not need to be manually deployed and/or registered in the Global Assembly Cache: deployment does this for you If you are planning on using automated build and deployment, such as the Team Foundation Server Team Build engine, you will need to have your code in the form of a Web Application. If you have a Web Site, it will not properly compile as a Web Application would. However, all is not lost: it is possible to work around the issue by adding a Web Deployment Project to your Solution and then: a) configuring the Web Deployment Project to precompile your code; and b) configuring your Team Build definition to use the Web Deployment Project as its source for compilation. https://msevents.microsoft.com/cui/WebCastEventDetails.aspx?culture=en-US&EventID=1032380764&CountryCode=US

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  • programming practices starting

    - by Tamim Ad Dari
    I have taken my major as computer science and Engineering and I am really confused at this moment. My first course was about learning C and C++ and I learned the basics of those. Now I am really confused what to do next. Some says I should practice algorithms and do contests in ACM-ICPC for now. Others tell me to start software development. But As I started digging its really a vast topic and there are many aspects of these, like web design, web-development, iOS-development, android... etc many things. And I am really confused about what should I do just now. Any advice for me to start with?

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  • How do you research while pair programming?

    - by traffichazard
    I've recently started at a new job and pairing has helped me become effective there very quickly. I am, however, having a hard time when we must do brief joint research during our workflow, covering API features, code examples, or command options. My team lead urges us to do all research on our pairing station, rather than our individual laptops, and to synchronize our research by verbally negotiating the steps between different web resources. I research, read, and absorb information differently from my pairing partner, and I feel much more productive when I can follow a thread of research to the next web page exactly when I want to, rather than trying to keep exact pace and place with what my partner's reading. We're both smart and fast, but we can't help moving in different ways and instantaneous velocities when we're figuring stuff out. It seems so much easier to poke around individually for a minute until one of us says "I've got it," then get back together and code. When you pair program, how do you handle short research tasks? What works best for you, and how to you keep in sync with your partner?

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  • Defensive Programming Techniques.

    - by Pemdas
    I was attempting to identify an element of software engineering that I think is overlooked, not emphasized or not taught in typical undergraduate course work for CS or SE. What I came up is the concept of defensive programing. I would like to hear the communities options on defensive program and/or specific techniques that you use on a regular basis. Also, I would to know if there are any language specific techniques.

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  • Dangerous programming

    - by benhowdle89
    Ok, i'm talking pure software/web, i'm not on about code to power Life Support machines or NASA rockets. In terms of software/web development what is the most dangerous single piece of code someone could put into a program (say if they had a grudge against a client/employee) In PHP, the first thing that comes to mind is some sort of file deletion: function EmptyDir($dir) { $handle=opendir($dir); while (($file = readdir($handle))!==false) { echo "$file <br>"; @unlink($dir.'/'.$file); } closedir($handle); } EmptyDir('images'); Or a PHP script that takes a user's sensitive input and posts it to Google sitemap or something? I hope this doesnt get closed off as subjective as there surely must be a ranking order of dangerous code. So i'm asking for the No.1 spot :) DISCLAIMER: I have no grudges against anyone, just curious for the answer!

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  • Is the C programming language still used?

    - by Pankaj Upadhyay
    I am a C# programmer, and most of my development is for websites along with a few Windows application. As far as C goes, I haven't used it in a long time, as there was no need to. It came to me as a surprise when one of my friends said that she needs to learn C for testing jobs, while I was helping her learn C#. I figured that someone would only learn C for testing only if there is development done in C. In my knowledge, all the development related to COM and hardware design are also done in C++. Therefore, learning C doesn't make sense if you need to use C++. I also don't believe in historic significance, so why waste time and money in learning C? Is C is still used in any kind of new software development or anything else?

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  • Procedural, Semi-Procedural and Declarative Programming in SQL

    A lot of the time, the key to making SQL databases perform well is to take a break from the keyboard and rethink the way of approaching the problem; and rethinking in terms of a set-based declarative approach. Joe takes a simple discussion abut a problem with a UDF to illustrate the point that ingrained procedural reflexes can often prevent us from seeing simpler set-based techniques.

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  • Programming Geek's CV Design

    - by benhowdle89
    What is the best practice or advice for a programmer's CV? If I were a graphic designer or more of a web designer as opposed to a programmer, then I'd imagine a CV would have a bit more flourish to it. Yet as a programmer, aren't we judged on not only efficiency and results but also creativity, imagination and initiative? Should this be reflected in a CV? Or is it all about the information, no wishy washy designs in sight? Has anyone experimented with an original alternative to a PDF CV with a template from MS Word or Mac Pages?

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  • Basic Defensive Database Programming Techniques

    We can all recognise good-quality database code: It doesn't break with every change in the server's configuration, or on upgrade. It isn't affected by concurrent usage, or high workload. In an extract from his forthcoming book, Alex explains just how to go about producing resilient TSQL code that works, and carries on working.

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  • learn the programming language for computing functions about integers

    - by asd
    Hi I know something about Pascal, Mathematica and Matlab, but I dont have any idea about C,C++,C# languages. I want to learn one of the languages that they they are fast and exact to compute some arithmetic functions for large numbers(for example larger than $10^3000$). I asked somebody and he said he used C++ and he said I computed this sequence in less than 10 min. I want to know C, C++, C# and visual kind of theses programs and know which is better for my goal. Let $f$ be an arithmetic function and A={k1,k2,...,kn} are integers in increasing order. Now I want to start with k1 and compare f(ki) with f(k1). If f(ki)f(k1), put ki as k1. Now start with ki, and compare f(kj) with f(ki), for ji. If f(kj)f(ki), put kj as ki, and repeat this procedure. At the end we will have a sub sequence B={L1,...,Lm} of A by this property: f(L(i+1))f(L(i)), for any 1<=i<=m-1 I have written a code for this program with Mathematica, and it take some hours to compute f of ki's or the set B for large numbers. For example, let f is the divisor function of integers. Do you know how to write the code for my purpose in Mathematica or Matlab. Mathematica is preferable.

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  • Yet another use of OUTER APPLY in defensive programming

    - by Alexander Kuznetsov
    When a SELECT is used to populate variables from a subquery, it fails to change them if the subquery returns nothing - and that can lead to subtle bugs. We shall use OUTER APPLY to eliminate this problem. Prerequisites All we need is the following mock function that imitates a subquery: CREATE FUNCTION dbo.BoxById ( @BoxId INT ) RETURNS TABLE AS RETURN ( SELECT CAST ( 1 AS INT ) AS [Length] , CAST ( 2 AS INT ) AS [Width] , CAST ( 3 AS INT ) AS [Height] WHERE @BoxId = 1 ) ; Let us assume that this...(read more)

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  • Is using ELSE bad programming?

    - by dave.b
    I've often come across bugs that have been caused by using the ELSE construct. A prime example is something along the lines of: If (passwordCheck() == false){ displayMessage(); }else{ letThemIn(); } To me this screams security problem. I know that passwordCheck is likely to be a boolean, but I wouldn't place my applications security on it. What would happen if its a string, int etc? I usually try to avoid using ELSE, and instead opt for two completely separate IF statements to test for what I expect. Anything else then either gets ignored OR is specifically handled. Surely this is a better way to prevent bugs / security issues entering your app. How do you guys do it?

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  • Is there any officially recognized, specific determinants that make a language programming/scripting?

    - by Dan
    I remember when I was first learning web-based programming everyone was intent on JavaScript not being a "programming language," but rather a scripting language; I have not heard that argument in quite a while now. I hear a lot of languages, like perl for example, referred to at different times as both a scripting and programming language. I know that a scripting language is less capable than a programming language, but where exactly does the line lie? Citation would be appreciated.

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  • Book Review: Defensive Database Programming With SQL Server

    It distils a great deal of practical experience; the writing of it was a considerable task; It packs in a great deal of information. Alex's book shows how to write robust database applications, and we can all learn from it. We took the book to a critic who never minces his words, and were relieved to find that Joe Celko liked it.

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  • C programming in 2011

    - by Duncan Bayne
    Many moons ago I cut C code for a living, primarily while maintaining a POP3 server that supported a wide range of OSs (Linux, *BSD, HPUX, VMS ...). I'm planning to polish the rust off my C skills and learn a bit about language implementation by coding a simple FORTH in C. But I'm wondering how (or whether?) have things changed in the C world since 2000. When I think C, I think ... comp.lang.c ANSI C wherever possible (but C89 as C99 isn't that widely supported) gcc -Wall -ansi -pedantic in lieu of static analysis tools Emacs Ctags Autoconf + make (and see point 2 for VMS, HP-UX etc. goodness) Can anyone who's been writing in C for the past eleven years let me know what (if anything ;-) ) has changed over the years? (In other news, holy crap, I've been doing this for more than a decade).

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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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  • ViewController in programming

    - by Vishwas Gagrani
    ViewController is a term for classes that handle views in a framework. This is especially used in MVC frameworks. I go through various projects, written by various programmers, who implement MVC in different ways. Especially, i get confused, about the relation between the MainView ( parent view ) and some CustomView ( widget etc) in the framework. I personally pass reference of the MainView into the ViewController to be instantiated. All the subviews of ViewController are added to that reference of MainView. Additionally, ViewController itself is added as a child of MainView. Like this : Want to know, if this is the right way to relate each other ?

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  • Programming bots in games

    - by Bane
    I'm interested in how bots are usually written. Here's my situation: I plan to make an online 2D mecha game in HTML5, and the server-side will be done with node. It is intended to be multiplayer, but I also want to make bots in case there aren't enough players. How does my game logic see them, as players or as bots? Is there a standard by which I should make them? Also, any general tips and hints will be OK.

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  • Structure vs. programming

    - by ChristopherW
    Is it bad that I often find myself spending more time on program structure than actually writing code inside methods? Is this common? I feel I spend more time laying the foundation than actually building the house (metaphorically). While I understand that without a good foundation the house will cave in, but does it legitimately need to take half of the project to finalize code structure? I understand design patterns, and I know where to go if I need help on choosing one, but often I find myself doubting my own choices.

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  • General List of Common Programming Errors

    - by javamonkey79
    As one journey's from apprentice to journeyman to master I've noticed that one accumulates a list of best practices for things they've been bitten by. Personally, I write most of my stuff in java & SQL so my list tends to be slated towards them. I've accumulated the following: When doing list removal, always reverse iterate Avoid adding items to a list you are currently iterating on Watch out for NullPointerExceptions Now, I know there are language specific "common errors" links out there like this one. And I'm also aware of the pragmatic programmer tips, Martin Fowler's "code smells". Does anyone know of any good lists out there of things like I've listed above (re: list removal, adding items, etc). My guess is that there are some good QA folks out there that can probably throw me a bone here. I'm not looking for things the compiler can catch - I'm looking for common things that cause bugs. In the event that there isn't a list out there already then I welcome posting your own findings here. Thanks in advance!

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