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• Am I "wasting" my time learning C and other low level stuff ?

  - by Andreas Grech

  I have just recently started learning C and the reason I did that was because frankly, I consider myself to be of a "less-developer" than the people who know and work with C. Thus I planned to start learning ASM, C, C++ and bought the K&R book and started pushing myself to learn the C Programming Language and up till now I'm doing great...learning about arrays the low level way (ie the pointer + offset thing), pointers and all that and obviously asking questions on stackoverflow for guidance. My problem is that sometimes I get thinking if instead of learning this low level stuff, maybe I should maybe spend more time learning newer, more widely used technologies...basically, more web stuff. Now I am well versed with both C# and ASP.Net and currently that's what I do for a living, but still there exists Microsoft technologies that I haven't quite touched upon...such as ASP.Net MVC, The Entity Framework etc... And those are only Microsoft Technologies...obviously there are other stuff that I would like to touch upon...stuff like Ruby, which would lead me to Ruby on Rails, or Python for Django or even Java and J2EE, or maybe even PHP; ie, basically mainly Web Stuff. Mind you, I did touch upon some of the stuff I mentioned earlier on, such as PHP and Java but I am still not quite versed in them as I am in C# and ASP.Net...but still, I think that by learning other languages that are used in the web environment will broaden my horizons...both as a developer who loves learning, and also Career wise. My point is, am I really using up my time correctly by learning older, lower level stuff? Stuff that for my current line of work, will most probably never use, but still is interesting to know ? To be frankly honest, I am also learning C so that I could, maybe someday, get into Electronics and Micro-controller programming but that is a whole new world for me and, if I choose to go there, will take some time to get adjusted to. And even then, I don't know if I can get a career in working in that line of work. ...but I still wonder about this question over and over...Am I doing the right thing by learning C instead of something (Web-stuff) that will most probably be more useful for me career-wise? I'm sorry for such asking such a long and most probably a boring question, but I feel as if this is the only place where I can ask such a question and get an honest answer from experts in the field. Thank you for your time.

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• Android app crashes when I change the default xml layout file to another

  - by mib1413456

  I am currently just starting to learn android development and have created a basic "Hello world" app that uses "activity_main.xml" for the default layout. I tried to create a new layout xml file called "new_layout.xml" with a text view, a text field and a button and did the following changes in the MainActivity.java file: setContentView(R.layout.new_layout); I did nothing else expect for adding a new_layout.xml in the res/layout folder, I have tried restarting and cleaning the project but nothing. Below is my activity_main.xml file, new_layout.xml file and MainActivity.java activity_main.xml: <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="org.example.androidsdk.demo.MainActivity" tools:ignore="MergeRootFrame" /> new_layout.xml: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > <TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="TextView" /> <EditText android:id="@+id/editText1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" android:ems="10" > <requestFocus /> </EditText> <Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Button" /> MainActivity.java file package org.example.androidsdk.demo; import android.app.Activity; import android.app.ActionBar; import android.app.Fragment; import android.os.Bundle; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.os.Build; public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.new_layout); if (savedInstanceState == null) { getFragmentManager().beginTransaction() .add(R.id.container, new PlaceholderFragment()) .commit(); } } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } /** * A placeholder fragment containing a simple view. */ public static class PlaceholderFragment extends Fragment { public PlaceholderFragment() { } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_main, container, false); return rootView; } } }

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• Scared of Calculus - Required to pass Differential Calculus as part of my Computer science major

  - by ke3pup

  Hi guys I'm finishing my Computer science degree in university but my fear of maths (lack of background knowledge) made me to leave all my maths units til' the very end which is now. i either take them on and pass or have to give up. I've passed all my programming units easily but knowing my poor maths skills won't do i've been staying clear of the maths units. I have to pass Differential Calculus and Linear Algebra first. With a help of book named "Linear Algebra: A Modern Introduction" i'm finding myself on track and i think i can pass the Linear Algebra unit. But with differential calculus i can't find a book to help me. They're either too advanced or just too simple for what i have to learn. The things i'm required to know for this units are: Set notation, the real number line, Complex numbers in cartesian form. Complex plane, modulus. Complex numbers in polar form. De Moivre’s Theorem. Complex powers and nth roots. Definition of ei? and ez for z complex. Applications to trigonometry. Revision of domain and range of a function Working in R3. Curves and surfaces. Functions of 2 variables. Level curves.Partial derivatives and tangent planes. The derivative as a difference quotient. Geometric significance of the derivative. Discussion of limit. Higher order partial derivatives. Limits of f(x,y). Continuity. Maxima and minima of f(x,y). The chain rule. Implicit differentiation. Directional derivatives and the gradient. Limit laws, l’Hoˆpital’s rule, composition law. Definition of sinh and cosh and their inverses. Taylor polynomials. The remainder term. Taylor series. Is there a book to help me get on track with the above? Being a student i can't buy too many books hence why i'm looking for a book that covers topics I need to know. The University library has a fairly limited collection which i took as loan but didn't find useful as it was too complex.

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• Simple JQuery Validator addMethod not working

  - by tehaaron

  Updated question on the bottom I am trying to validate a super simple form. Eventually the username will be compared to a RegExp statement and the same will go for the password. However right now I am just trying to learn the Validator addMethod format. I currently have this script: JQuery.validator.addMethod( "legalName", function(value, element) { if (element.value == "bob") { return false; } else return true; }, "Use a valid username." ); $(document).ready(function() { $("#form1").validate({ rules: { username: { legalName: true } }, }); }); Which if I am not mistaken should return false and respond with "Use a valid username." if I were to put "bob" into the form. However, it is simply submitting it. I am linking to JQuery BEFORE Validator in the header like instructed. My uber simple form looks like this: <form id="form1" method="post" action=""> <div class="form-row"><span class="label">Username *</span><input type="text" name="username" /></div> <div class="form-row"><input class="submit" type="submit" value="Submit"></div> </form> Finally how would I go about restructing the addMethod function to return true if and false at the else stage while keeping the message alert for a false return? (ignore this last part if you don't understand what I was trying to say :) ) Thanks in advance. Thank to everyone who pointed out my JQuery - jQuery typo. New Ideally, I am trying to turn this into a simple login form (username/password). It is for demonstration only so it wont have a database attached or anything, just some simple js validations. I am looking to make the username validate for <48 characters, only english letters and numbers, no special characters. I thought a whitelist would be easiest so I had something like this: ^[a-zA-Z0-9]*${1,48} but I am not sure if that is proper JS RegExp (it varies from Ruby RegExp if I am not mistaken?...Usually I use rubular.com). Password will be similar but require some upper/lowercase and numbers. I believe I need to make another $.validator.addMethod for legalPassword that will look very similar.

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• How to setup a webserver in common lisp?

  - by Serpico

  Several months ago, I was inspired by the magnificent book ANSI Common Lisp written by Paul Graham, and the statement that Lisp could be used as a secret weapon in your web development, published by the same author on his blog. Wow, that is amazing. That is something that I have been looking for long time. The author really developed a successful web applcation and sold it to Yahoo. With those encouraging images, I determined to spend some time (1 year or 2 year, who knows) on learning Common Lisp. Maybe someday I will development my web application and turn into a great Lisp expert. In fact, this is the second time for me to get to study Lisp. The first time was a couple of years ago when I was fascinated by the famous book SICP but found later Scheme was so unbelievably immature for real life application. After reading some chapters of ANSI Common Lisp, I was pretty sure that is a great book full of detailed exploration of Common Lisp. Then I began to set up a web server in Common Lisp. After all, this should be the best way if you want to learn something. Demonstrations are always better than definations. As suggested by the book Practical Common Lisp (by the way, this is also a great book), I chose to install AllegroServe on some Common Lisp implementation. Then, from somewhere else, I learned that Hunchentoot seems to be better than AllegroServe. (I don't remember where and whom this word is from. So don't argue with me.) Ironically, you know what, I never could installed the two packages on any Common Lisp implementation. More annoyingly, I even don't know why. The machine always spit up a lot of jargon and lead me into a chaos. I've tried searching the internet and have not found anything. Could anybody who has successfully installed these packages in Linux tell me how you did it? Have you run into any trouble? How did you figured out what is wrong and fixed it? The more detailed, the more helpful.

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• How to run an application as root without asking for an admin password?

  - by kvaruni

  I am writing a program in Objective-C (XCode 3.2, on Snow Leopard) that is capable of either selectively blocking certain sites for a duration or only allow certain sites (and thus block all others) for a duration. The reasoning behind this program is rather simple. I tend to get distracted when I have full internet access, but I do need internet access during my working hours to get to a number of work-related websites. Clearly, this is not a permanent block, but only helps me to focus whenever I find myself wandering a bit too much. At the moment, I am using a Unix script that is called via AppleScript to obtain Administrator permissions. It then activates a number of ipfw rules and clears those after a specific duration to restore full internet access. Simple and effective, but since I am running as a standard user, it gets cumbersome to enter my administrator password each and every time I want to go "offline". Furthermore, this is a great opportunity to learn to work with XCode and Objective-C. At the moment, everything works as expected, minus the actual blocking. I can add a number of sites in a list, specify whether or not I want to block or allow these websites and I can "start" the blocking by specifying a time until which I want to stay "offline". However, I find it hard to obtain clear information on how I can run a privileged Unix command from Objective-C. Ideally, I would like to be able to store information with respect to the Administrator account into the Keychain to use these later on, so that I can simply move into "offline" mode with the convenience of clicking a button. Even more ideally, there might be some class in Objective-C with which I can block access to some/all websites for this particular user without needing to rely on privileged Unix commands. A third possibility is in starting this program with root permissions and the reducing the permissions until I need them, but since this is a GUI application that is nested in the menu bar of OS X, the results are rather awkward and getting it to run each and every time with root permission is no easy task. Anyone who can offer me some pointers or advice? Please, no security-warnings, I am fully aware that what I want to do is a potential security threat.

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• Login Script for PostGreSQL and PHP not working =[

  - by MrEnder

  Ok I'm quite new at logins what not so bare with me here lol but I gota learn so don't discourage me. I tried this so far <?php $error = ""; $conn = pg_connect("host=localhost dbname=brittains_db user=brittains password=XXXX" ); $sql = "SELECT * FROM logins"; $result = pg_query($conn, $sql); if($_SERVER["REQUEST_METHOD"] == "GET") { $userName=""; $password=""; } else if($_SERVER["REQUEST_METHOD"] == "POST") { $userName=trim($_POST["userNameLogin"]); $password=trim($_POST["passwordLogin"]); if(pg_fetch_result($results, $userName, "userName")==true && pg_fetch_result($results, $password, "userName")==true) { setcookie("userIDforDV", $userName, time()+43200); } else { $error = "Your username and or password is incorrect"; } } $userName = $_COOKIE['userIDforDV']; if(isset($userName) && $userName!="") { echo "Welcome " . $userName; } echo $error; ?> <form> <table> <tr> <td class="signupTd"> User Name:&nbsp; </td> <td> <input type="text" name="userNameLogin" value="" size="20" /> </td> </tr> <tr> <td class="signupTd"> Password:&nbsp; </td> <td> <input type="password" name="passwordLogin" value="" size="20" /> </td> </tr> <tr> <td class="signupTd" colspan="2"> <input type="submit" name="submit" value="Submit"/> </td> </tr> </table> </form> that was the idea I came up with... but its prolly a really bad idea and it doesn't work... how might I go about this properly? I need really detailed descriptions please. Thanks a tun Shelby

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• Going from a math career to a cs career: how to do it?

  - by Joseph

  Hey, I'm looking for some advice on how to successfully make the transition from mathematics to CS. My academic background is in mathematics (BS and MSc), and I've taken loads of math courses as well. You name it, and I took it: Measure Theory, Algebra, PDES, Manifolds, Complex Analysis, etc. I progressed quite far along this track, and at one point, I thought I would be a professional mathematician...But around the time I was finishing my MSc, I really got sick of it. Studying very abstract mathematics was fun, but it really lost it's appeal to me. Outside of a couple hundred people, I'm not sure if anybody would understand my research. I did not want to be 60 years old and say that my only contribution to the world consisted of published papers. Anyways, I've been an off and on hobbyist programmer since 2002. I've programmed in C and Java (just small projects), and I really started to be drawn to the area as time passed. There's a real appeal to CS work because, well, it actually means something to other people out there! I enjoy all parts of it: designing webpages (a real artistic appeal). On the other end, I do enjoy toying with compilers and more nitty-gritty stuff as well. Suffice to say, I have broad interests out there. Anyways, I know it's a bit late, but I was wondering if there were other folks out there who made the change, and if so, how I could do so. I know I have some fairly big gaps to fill in terms of data structures, lack of internship experience, etc. But I really would like to make this work. So my question is simply: How can I make the switch from math to CS? To pay the bills, I'll be doing financial analysis for a company, but I'd like to eventually transition into a developer type position. I've been reading "Algorithm Design" by Tardos and doing all the problems. It's not hard to make progress since the problems are far more concrete than the stuff I've been doing the past six years. I feel I can make fairly rapid progress in picking up all the materials from data structures, etc. but none of it can substitute the past several years I've lost. Anyways, I'm eager to learn but would love some advice/concrete direction. Thanks, Joseph

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• Git repo planning questions

  - by masonk

  At work, development uses perforce to handle code sharing. I won't say "revision control", because we aren't allowed to check in changes until they are ready for regression testing. In order to get my personal change sets under revision control, I've been given the go-ahead to build my own git and initialize the client view of the perforce depot as a git repo. There are some difficulties in doing this, however. The client view lives in a subfolder of ~, (~/p4), and I want to put ~ under revision control as well, with its own separate history. I can't figure out how to keep the history for ~ separate from ~/p4 without using a submodule. The problem with a submodule is that it looks like I have to go make a repository that will become the submodule and then git submodule add <repo> <path>. But there is nowhere to make the submodule's repository except in ~. There seems to be no safe place to create the initial client view of the depot with git p4 clone. (I'm working off of the assumption that initing or cloning a repo into a subdirectory of a git repo is not supported. At least, I can find nothing authoritative on nested git repos.) edit: Is merely ignoring ~/p4 in the repo rooted at ~ enough to allow me to init a nested repo in ~/p4? My __git_ps1 function still thinks I'm in a git repository when I visit an ignored subdirectory of a git repo, so I'm inclined to think not. I need the "remote" repository created by git p4 sync to be a branch in ~/p4. We are required to keep all of our code in ~/p4 so that it doesn't get backed up. Can I pull from a "remote" branch that is really a local branch? This one is just for convenience, but I thought I could learn something by asking it. For 99% of the project, I just want to start the with the p4 head revision as the inital commit object. For the other 1%, I would like to suck down the entire p4 history so that I can browse it in git. IOW, after I'm done initalizing it, the initial commit of remotes/p4/master branch will contain: revision 1 of //depot/prod/Foo/Bar/* revision X of other files in //depot/prod/*, where X is the head revision and the remotes/p4/master branch contains Y commits, where Y is the number of changelists that had a file in //depot/prod/Foo/Bar/*, with each commit in the history corresponding to one of those p4 changelists, and HEAD looking like p4's head.

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• Git/Mercurial (hg) opinion

  - by Richard

  First, let me say I'm not a professional programmer, but an engineer who had a need for it and had to learn. I was always working alone, so it was just me and my seven splitted personalities ... and we worked okey as a team :) Most of my stuff is done in C/Fortran/Matlab and so far I've been learning git to manage it all. However, although I've had no unsolvable problems with it, I've never been "that" happy with it ... for everything I cannot do, I hae to look up a book. And, for some time now I've been hearning a lot of good stuff about hg. Now, a coleague of mine will have to work with me on a project (I almost feel sorry for him) and he's started learning hg (says he likes it more), and I'm considering the switch myself. We work almost exclusivly on Windows platform (although I manage relatively ok using unix tools and things that come from that part of the world). So, I was wondering, in a described scenario, what problems could I expect with the switch. I heard that hg is rather more user friendly towards windows users, regarding the user interfaces. How does it handle repositories ? Does it create them the same way as git does (just one subdirectory in a working directory) and can I just copy the whole project directory (including git repo) and just carry them somewhere with no extra thinking ? (I really liked that when I was choosing over git/svn). Are there any good books on it that you can recommend (something like Pro Git, only for Hg). What are good ways to implement hg into Visual Studio/GVim for Windows, or into Windows Explorer so I can work relatively easily (I would like to avoid using the command line for everything regarding it, like in git shell). Is there something else I should be aware of (please, on this don't point me to other questions ... they just give me a ton of info, and I'm not sure what is it that I should take as important, and what to disregard). I'm trying to cut some time, since I cannot spend all that time relearning hg, like I did for git. I've also heard git is c project, while mercurial is python ... is there any noticeable difference in speed. git was pretty speedy ... will I encounter some waiting while working. Notice: All my projects are of let's say, middle size ... mostly numerical simulations ... 10-15000 lines (medium size?)

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• Where to put a glossary of important terms and patterns in documentation?

  - by Tetha

  Greetings. I want to document certain patterns in the code in order to build up a consistent terminology (in order to easen communication about the software). I am, however, unsure, where to define the terms given. In order to get on the same level, an example: I have a code generator. This code generator receives a certain InputStructure from the Parser (yes, the name InputStructure might be less than ideal). This InputStructure is then transformed into various subsequent datastructures (like an abstract description of the validation process). Each of these datastructures can be either transformed into another value of the same datastructure or it can be transformed into the next datastructure. This should sound like Pipes and Filters to some degree. Given this, I call an operation which takes a datastructures and constructs a value of the same datastructure a transformation, while I call an operation which takes a datastructure and produces a different follow-up datastructure a derivation. The final step of deriving a string containing code is called emitting. (So, overall, the codegenerator takes the input-structure and transforms, transforms, derives, transforms, derives and finally emits). I think emphasizing these terms will be benefitial in communications, because then it is easy to talk about things. If you hear "transformation", you know "Ok, I only need to think about these two datastructures", if you hear "emitting", you know "Ok, I only need to know this datastructure and the target language.". However, where do I document these patterns? The current code base uses visitors and offers classes called like ValidatorTransformationBase<ResultType> (or InputStructureTransformationBase<ResultType>, and so one and so on). I do not really want to add the definition of such terms to the interfaces, because in that case, I'd have to repeat myself on each and every interface, which clearly violates DRY. I am considering to emphasize the distinction between Transformations and Derivations by adding further interfaces (I would have to think about a better name for the TransformationBase-classes, but then I could do thinks like ValidatorTransformation extends ValidatorTransformationBase<Validator>, or ValidatorDerivationFromInputStructure extends InputStructureTransformation<Validator>). I also think I should add a custom page to the doxygen documentation already existing, as in "Glossary" or "Architecture Principles", which contains such principles. The only disadvantage of this would be that a contributor will need to find this page in order to actually learn about this. Am I missing possibilities or am I judging something wrong here in your opinion? -- Regards, Tetha

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• PHP-based LaTeX parser -- where to begin?

  - by Alex Basson

  The project: I want to build a LaTeX-to-MathML translator in PHP. Why? Because I'm a mathematician, and I want to publish math on my Drupal site. It doesn't have to translate all of LaTeX, since the basic document-level stuff is ably handled by the CMS and wouldn't be written in LaTeX to begin with; it just has to translate math written in LaTeX into math written in MathML. Although I feel as though I've done my due diligence, this doesn't seem to exist already. Maybe I'm wrong---if you know of something that would serve this purpose, by all means let me know, and thank you in advance. But assuming it doesn't exist, I guess I have to go write it myself. Here's the thing, though: I've never done anything this ambitious. I don't really know where to begin. I've used PHP for years, but just to do the standard "build a CMS with PHP and MySQL"-type of stuff. I've never attempted anything as seemingly sophisticated as translation from one language to another. I'm just dumb enough to consider doing it with regex---after all, LaTeX is a much more formal language, and it doesn't allow for nearly the kinds of pathological edge-cases, as say, HTML. But on the other hand, I'm just smart enough to realize this is probably a terrible idea: now I have two problems, and I sure don't want to end up like this guy. So if that's not the way to go (right?), what is? How should I start thinking about this problem? Am I essentially writing a LaTeX compiler in PHP, and if so, what do I need to know to do that (like, should I just go read the Purple Dragon book first?)? I'm both really excited and pretty intimidated by the prospect of this project, but hey, this is how we all learn to be programmers, right? If something we need doesn't exist, we go and build it, necessity is the mother of... you get the point. Tremendous thanks to everyone in advance for any and all guidance you can offer.

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• Hidden Features of PHP?

  - by George Mauer

  EDIT: This didn't really start as a hidden features of PHP topic, but thats what it ended up as, so go nuts. I know this sounds like a point-whoring question but let me explain where I'm coming from. Out of college I got a job at a PHP shop. I worked there for a year and a half and thought that I had learned all there was to learn about programming. Then I got a job as a one-man internal development shop at a sizable corporation where all the work was in C#. In my commitment to the position I started reading a ton of blogs and books and quickly realized how wrong I was to think I knew everything. I learned about unit testing, dependency injection and decorator patterns, the design principle of loose coupling, the composition over inheritance debate, and so on and on and on - I am still very much absorbing it all. Needless to say my programming style has changed entirely in the last year. Now I find myself picking up a php project doing some coding for a friend's start-up and I feel completely constrained as opposed to programming in C#. It really bothers me that all variables at a class scope have to be referred to by appending '$this-' . It annoys me that none of the IDEs that I've tried have very good intellisense and that my SimpleTest unit tests methods have to start with the word 'test'. It drives me crazy that dynamic typing keeps me from specifying implicitly which parameter type a method expects, and that you have to write a switch statement to do method overloads. I can't stand that you can't have nested namespaces and have to use the :: operator to call the base class's constructor. Now I have no intention of starting a PHP vs C# debate, rather what I mean to say is that I'm sure there are some PHP features that I either don't know about or know about yet fail to use properly. I am set in my C# universe and having trouble seeing outside the glass bowl. So I'm asking, what are your favorite features of PHP? What are things you can do in it that you can't or are more difficult in the .Net languages?

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• Linked List Design

  - by Jim Scott

  The other day in a local .NET group I attend the following question came up: "Is it a valid interview question to ask about Linked Lists when hiring someone for a .NET development position?" Not having a computer sciense degree and being a self taught developer my response was that I did not feel it was appropriate as I in 5 years of developer with .NET had never been exposed to linked lists and did not hear any compeling reason for a use for one. However the person commented that it is a very common interview question so I decided when I left that I would do some reasearch on linked lists and see what I might be missing. I have read a number of posts on stack overflow and various google searches and decided the best way to learn about them was to write my own .NET classes to see how they worked from the inside out. Here is my class structure Single Linked List Constructor public SingleLinkedList(object value) Public Properties public bool IsTail public bool IsHead public object Value public int Index public int Count private fields not exposed to a property private SingleNode firstNode; private SingleNode lastNode; private SingleNode currentNode; Methods public void MoveToFirst() public void MoveToLast() public void Next() public void MoveTo(int index) public void Add(object value) public void InsertAt(int index, object value) public void Remove(object value) public void RemoveAt(int index) Questions I have: What are typical methods you would expect in a linked list? What is typical behaviour when adding new records? For example if I have 4 nodes and I am currently positioned in the second node and perform Add() should it be added after or before the current node? Or should it be added to the end of the list? Some of the designs I have seen explaining things seem to expose outside of the LinkedList class the Node object. In my design you simply add, get, remove values and know nothing about any node object. Should the Head and Tail be placeholder objects that are only used to define the head/tail of the list? I require my Linked List be instantiated with a value which creates the first node of the list which is essentially the head and tail of the list. Would you change that ? What should the rules be when it comes to removing nodes. Should someone be able to remove all nodes? Here is my Double Linked List Constructor public DoubleLinkedList(object value) Properties public bool IsHead public bool IsTail public object Value public int Index public int Count Private fields not exposed via property private DoubleNode currentNode; Methods public void AddFirst(object value) public void AddLast(object value) public void AddBefore(object existingValue, object value) public void AddAfter(object existingValue, object value) public void Add(int index, object value) public void Add(object value) public void Remove(int index) public void Next() public void Previous() public void MoveTo(int index)

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• Learning to create beautiful /next-generation GUI

  - by ShaChris23

  I really want to create a stunning-looking GUI desktop application that looks like, for example: Mac OS X interface Picasa desktop client on windows IPhone apps Office 2007 I've mostly been programming GUI using Qt/Swing/WinForm and I'm tired of creating so plain looking GUI, lol. So I was thinking about diving into stuff like: jQuery WPF/C# iPhone SDK Silverlight Adobe Air/Flex Just to get some ideas on how to create really cool looking UI. Does that sound like a good list? Any developers here that could share what platform they use to create very cool looking desktop app? On a sidenote, I really wonder what developers at Apple / Microsoft use to develop their own cool-looking software. EDIT A lot of responses talk about the importance of usability over "cool-looking".. I totally agree that usability and simplicity are the most important aspects of user interface design. I've been doing GUI development for a while now ( 3 years), so that I understand. But using cool-looking UI also improves user experience + it could make big difference on whether or not your software sells. I mean, otherwise why would Microsoft/Apple try to make their OS UI look "cooler" everytime there's a new version? Why would websites like pragprog.com, or versionsapp.com. make their websites look like that? Basically you kill 2 birds with one stone: stunnning-looking UI + super usability (because it looks simple and intuitive). That is what I'm striving for. And as far as I know, I cannot achieve that using Qt/Winform. Most of the books I have read just show you how to make average-looking (read: 1990's) UI. I want to learn how to create cool-looking UI. And the only place I see cool-looking UIs these days are the technology I list above. I'm not enamored with any technology; but I just want to know how things are done in other technology to see if I could apply them to the technology I'm using, or see if I could use those technology in my line of work. An example: if I were to pick between this UI and this UI, I probably would pick the latter, if just based on looks alone. Functionally, they are just the same UI; they both allow you to keep track of your time. They both contain buttons and textboxes, etc. But the fact that they look different, also differentiate them in terms of attractiveness. So in all, I think the "ice on the cake" is very important. I would say it's the thing you strive for after you are certain you have a totally intuitive, usable UI.

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• jQuery jScrollPane - it simply won't work! :'(

  - by Jack Webb-Heller

  Hey folks, OK - I'll admit, I'm quite a beginner in this jQuery-department. I've probably made some amateur mistake, but hey, you gotta learn somewhere! :) So I'm using jScrollPane: http://www.kelvinluck.com/assets/jquery/jScrollPane/jScrollPane.html I want to use it style the scrollable area in my second column. Specifically, I would like to apply and format the scrollbars on the div #ajaxresults My page is... rather jQuery heavy. I don't know if any variables are conflicting or something... in fact I really have no idea at all why this isn't working. Take a look at my problematic page: http://furnace.howcode.com In the header, I've set this to go: <!-- Includes for jScrollPane --> <script type="text/javascript" src="http://localhost:8888/js/jquery.mousewheel.min.js"></script> <script type="text/javascript" src="http://localhost:8888/js/jScrollPane.js"></script> <link rel="stylesheet" type="text/css" media="all" href="http://localhost:8888/stylesheets/jScrollPane.css" /> <script type="text/javascript"> $(function() { $('#ajaxresults').jScrollPane(); }); </script> (I've changed localhost on the server copy though) Nothing ever seems to work with the #ajaxresults div. I've set, as the jScrollPane docs say, overflow:auto on it but still no luck. I find that when jScrollPane DOES seem to 'run' it just moves the div down about 100 pixels. Try it for yourself. Perhaps someone could help? There's quite a few jQuery plugins there so I don't know if something's colliding/crashing etc... Please note the site is still in development between myself and a friend, which explains the personal messages we submit to each other ('Hi Donnie!' etc. :D ). Also, when you view the page nothing may appear in the second column for a few seconds - it's just fetching the data via Ajax. So give it a little time. Thanks very much! Jack

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• MySQL table organization and optimization (Rails)

  - by aguynamedloren

  I've been learning Ruby on Rails over the past few months with no prior programming experience. Lately, I've been thinking about database optimization and table organization. I know there are great books on the subject, but I typically learn by example / as I go. Here's a hypothetical situation: Let's say I am building a social network for a niche community with 250,000 members (users). The users have the ability to attend events. Let's say there are 50,000 past/present/future events. Much like Facebook events, a user can attend any number of events and an event can have any number of attendees. In the database, there would be a table for users and a table for events. Somehow I would have to create an association between the users and events. I could create an "events" column in the users table such that each user row would contain a hash of event IDs, or I could create an "attendees" column in the events table such that each event row would contain a hash of user IDs. Neither of these solutions seem ideal, however. On a users profile page, I want to display the list of events they are associated with, which would require scanning the 50,000 event rows for the user ID of said user if I include an "attendees" column in the events table. Likewise, on an event page, I want to display a list of attendees for the event, which would require scanning the 250,000 user rows for the event ID of said event if I include an "events" column in the users table. Option 3 would be to create a third table that contains the attendee information for each and every event - but I don't see how this would solve any problems. Are these non-issues? Rails makes accessing all of this information easy, but I guess I'm worried about scale. It is entirely possible that I am under-estimating the speed and processing power of modern databases / servers / etc. How long would it take to scan 250,000 user rows for specific event IDs - 10ms? 100ms? 1,000ms? I guess that's not that bad. Am I just over-thinking this?

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• Mercurial for Beginners: The Definitive Practical Guide

  - by Laz

  Inspired by Git for beginners: The definitive practical guide. This is a compilation of information on using Mercurial for beginners for practical use. Beginner - a programmer who has touched source control without understanding it very well. Practical - covering situations that the majority of users often encounter - creating a repository, branching, merging, pulling/pushing from/to a remote repository, etc. Notes: Explain how to get something done rather than how something is implemented. Deal with one question per answer. Answer clearly and as concisely as possible. Edit/extend an existing answer rather than create a new answer on the same topic. Please provide a link to the the Mercurial wiki or the HG Book for people who want to learn more. Questions: Installation/Setup How to install Mercurial? How to set up Mercurial? How do you create a new project/repository? How do you configure it to ignore files? Working with the code How do you get the latest code? How do you check out code? How do you commit changes? How do you see what's uncommitted, or the status of your current codebase? How do you destroy unwanted commits? How do you compare two revisions of a file, or your current file and a previous revision? How do you see the history of revisions to a file? How do you handle binary files (visio docs, for instance, or compiler environments)? How do you merge files changed at the "same time"? Tagging, branching, releases, baselines How do you 'mark' 'tag' or 'release' a particular set of revisions for a particular set of files so you can always pull that one later? How do you pull a particular 'release'? How do you branch? How do you merge branches? How do you merge parts of one branch into another branch? Other Good GUI/IDE plugin for Mercurial? Advantages/disadvantages? Any other common tasks a beginner should know? How do I interface with Subversion? Other Mercurial references Mercurial: The Definitive Guide Mercurial Wiki Meet Mercurial | Peepcode Screencast

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• Optimizing Haskell code

  - by Masse

  I'm trying to learn Haskell and after an article in reddit about Markov text chains, I decided to implement Markov text generation first in Python and now in Haskell. However I noticed that my python implementation is way faster than the Haskell version, even Haskell is compiled to native code. I am wondering what I should do to make the Haskell code run faster and for now I believe it's so much slower because of using Data.Map instead of hashmaps, but I'm not sure I'll post the Python code and Haskell as well. With the same data, Python takes around 3 seconds and Haskell is closer to 16 seconds. It comes without saying that I'll take any constructive criticism :). import random import re import cPickle class Markov: def __init__(self, filenames): self.filenames = filenames self.cache = self.train(self.readfiles()) picklefd = open("dump", "w") cPickle.dump(self.cache, picklefd) picklefd.close() def train(self, text): splitted = re.findall(r"(\w+|[.!?',])", text) print "Total of %d splitted words" % (len(splitted)) cache = {} for i in xrange(len(splitted)-2): pair = (splitted[i], splitted[i+1]) followup = splitted[i+2] if pair in cache: if followup not in cache[pair]: cache[pair][followup] = 1 else: cache[pair][followup] += 1 else: cache[pair] = {followup: 1} return cache def readfiles(self): data = "" for filename in self.filenames: fd = open(filename) data += fd.read() fd.close() return data def concat(self, words): sentence = "" for word in words: if word in "'\",?!:;.": sentence = sentence[0:-1] + word + " " else: sentence += word + " " return sentence def pickword(self, words): temp = [(k, words[k]) for k in words] results = [] for (word, n) in temp: results.append(word) if n > 1: for i in xrange(n-1): results.append(word) return random.choice(results) def gentext(self, words): allwords = [k for k in self.cache] (first, second) = random.choice(filter(lambda (a,b): a.istitle(), [k for k in self.cache])) sentence = [first, second] while len(sentence) < words or sentence[-1] is not ".": current = (sentence[-2], sentence[-1]) if current in self.cache: followup = self.pickword(self.cache[current]) sentence.append(followup) else: print "Wasn't able to. Breaking" break print self.concat(sentence) Markov(["76.txt"]) -- module Markov ( train , fox ) where import Debug.Trace import qualified Data.Map as M import qualified System.Random as R import qualified Data.ByteString.Char8 as B type Database = M.Map (B.ByteString, B.ByteString) (M.Map B.ByteString Int) train :: [B.ByteString] -> Database train (x:y:[]) = M.empty train (x:y:z:xs) = let l = train (y:z:xs) in M.insertWith' (\new old -> M.insertWith' (+) z 1 old) (x, y) (M.singleton z 1) `seq` l main = do contents <- B.readFile "76.txt" print $ train $ B.words contents fox="The quick brown fox jumps over the brown fox who is slow jumps over the brown fox who is dead."

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• How do I add a custom view to iPhone app's UI?

  - by Dr Dork

  I'm diving into iPad development and I'm still learning how everything works together. I understand how to add standard view (i.e. buttons, tableviews, datepicker, etc.) to my UI using both Xcode and Interface Builder, but now I'm trying to add a custom calendar control (TapkuLibrary) to the left window in my UISplitView application. My question is, if I have a custom view (in this case, the TKCalendarMonthView), how do I programmatically add it to one of the views in my UI (in this case, the RootViewController)? Below are some relevant code snippets from my project... RootViewController interface @interface RootViewController : UITableViewController <NSFetchedResultsControllerDelegate> { DetailViewController *detailViewController; NSFetchedResultsController *fetchedResultsController; NSManagedObjectContext *managedObjectContext; } @property (nonatomic, retain) IBOutlet DetailViewController *detailViewController; @property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController; @property (nonatomic, retain) NSManagedObjectContext *managedObjectContext; - (void)insertNewObject:(id)sender; TKCalendarMonthView interface @class TKMonthGridView,TKCalendarDayView; @protocol TKCalendarMonthViewDelegate, TKCalendarMonthViewDataSource; @interface TKCalendarMonthView : UIView { id <TKCalendarMonthViewDelegate> delegate; id <TKCalendarMonthViewDataSource> dataSource; NSDate *currentMonth; NSDate *selectedMonth; NSMutableArray *deck; UIButton *left; NSString *monthYear; UIButton *right; UIImageView *shadow; UIScrollView *scrollView; } @property (readonly,nonatomic) NSString *monthYear; @property (readonly,nonatomic) NSDate *monthDate; @property (assign,nonatomic) id <TKCalendarMonthViewDataSource> dataSource; @property (assign,nonatomic) id <TKCalendarMonthViewDelegate> delegate; - (id) init; - (void) reload; - (void) selectDate:(NSDate *)date; Thanks in advance for all your help! I still have a ton to learn, so I apologize if the question is absurd in any way. I'm going to continue researching this question right now!

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• jqModal and jquery widget long shot

  - by rod

  Hi All, I just started playing around with jquery widgets within my jqmodals in my mvc app. I know this may be a long shot but I'll take it. Initially, I can click the Add link, get the alert ("which is the prize", watching too much tv), next click cancel to close modal and get the desired results. I can, then, click the Edit link and get the same desired results. However, if I click Edit link first then I try to click the Add link, "forget about it" I don't get the alert (which means my widget did not init). But I can still go back and click Edit and get the prize (the alert message). ajax: "/Home/EditPrintAdLine" and ajax: "/Home/AddPrintAdLine" render the same web user control Any ideas? <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" %> <asp:Content ID="indexTitle" ContentPlaceHolderID="TitleContent" runat="server"> Home Page </asp:Content> <asp:Content ID="indexContent" ContentPlaceHolderID="MainContent" runat="server"> <h2><%= Html.Encode(ViewData["Message"]) %></h2> <p> To learn more about ASP.NET MVC visit <a href="http://asp.net/mvc" title="ASP.NET MVC Website">http://asp.net/mvc</a>. </p> <div id="printAdLineEditDialog" class="jqmWindow"></div> <div id="printAdDialog" class="jqmWindow"></div> <table> <tr><td><a id="printAdLineItem" href="#">Add a Line Item</a></td></tr> <tr><td><a id="editPrintAdLine" href="#">Edit</a></td></tr> </table> <script type="text/javascript"> $(document).ready(function() { $.widget("ui.my_widget", { _init: function() { alert("My widget was instantiated"); } }); // Add line $('#printAdLineItem').click(function(e) { $('#printAdDialog').jqmShow(this); e.preventDefault(); }); $('#printAdDialog').jqm({ ajax: "/Home/AddPrintAdLine", onLoad: function(hash) { $('#PrintAdLine_RunDate').my_widget(); } }); // Edit line $('#editPrintAdLine').click(function(e) { $('#printAdLineEditDialog').jqmShow(this); e.preventDefault(); }); $('#printAdLineEditDialog').jqm({ ajax: "/Home/EditPrintAdLine", onLoad: function(hash) { $('#PrintAdLine_RunDate').my_widget(); } }); }); </script> </asp:Content>

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• [NEWVERSION]algorithm || method to write prog[UNSOLVED] [closed]

  - by fatai

  I am one of the computer science student. Everyone solve problem with a different or same method, ( but actually I dont know whether they use method or I dont know whether there are such common method to approach problem.) if there are common method, What is it ? If there are different method, which method are you using ? All teacher give us problem which in simple form sometimes, but they donot introduce any approach or method(s) so that we cannot make a decision to choose the method then apply that one to problem , afterward find solution then write code.No help from teacher , push us to find method to solve homework. Ex: my friend is using no method , he says "I start to construct algorithm while I try to write prog." I have found one method when I failed the course, More accurately, my method: When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 now, my other question is ; What is/are other method(s) which have/has been; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c by other user? Some programmer uses generalized method without considering prog-language(java , perl .. ), what is this method ? Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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• TicTacToe AI Making Incorrect Decisions

  - by Chris Douglass

  A little background: as a way to learn multinode trees in C++, I decided to generate all possible TicTacToe boards and store them in a tree such that the branch beginning at a node are all boards that can follow from that node, and the children of a node are boards that follow in one move. After that, I thought it would be fun to write an AI to play TicTacToe using that tree as a decision tree. TTT is a solvable problem where a perfect player will never lose, so it seemed an easy AI to code for my first time trying an AI. Now when I first implemented the AI, I went back and added two fields to each node upon generation: the # of times X will win & the # of times O will win in all children below that node. I figured the best solution was to simply have my AI on each move choose and go down the subtree where it wins the most times. Then I discovered that while it plays perfect most of the time, I found ways where I could beat it. It wasn't a problem with my code, simply a problem with the way I had the AI choose it's path. Then I decided to have it choose the tree with either the maximum wins for the computer or the maximum losses for the human, whichever was more. This made it perform BETTER, but still not perfect. I could still beat it. So I have two ideas and I'm hoping for input on which is better: 1) Instead of maximizing the wins or losses, instead I could assign values of 1 for a win, 0 for a draw, and -1 for a loss. Then choosing the tree with the highest value will be the best move because that next node can't be a move that results in a loss. It's an easy change in the board generation, but it retains the same search space and memory usage. Or... 2) During board generation, if there is a board such that either X or O will win in their next move, only the child that prevents that win will be generated. No other child nodes will be considered, and then generation will proceed as normal after that. It shrinks the size of the tree, but then I have to implement an algorithm to determine if there is a one move win and I think that can only be done in linear time (making board generation a lot slower I think?) Which is better, or is there an even better solution?

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• Reliable and fast way to convert a zillion ODT files in PDF?

  - by Marco Mariani

  I need to pre-produce a million or two PDF files from a simple template (a few pages and tables) with embedded fonts. Usually, I would stay low level in a case like this, and compose everything with a library like ReportLab, but I joined late in the project. Currently, I have a template.odt and use markers in the content.xml files to fill with data from a DB. I can smoothly create the ODT files, they always look rigth. For the ODT to PDF conversion, I'm using openoffice in server mode (and PyODConverter w/ named pipe), but it's not very reliable: in a batch of documents, there is eventually a point after which all the processed files are converted into garbage (wrong fonts and letters sprawled all over the page). Problem is not predictably reproducible (does not depend on the data), happens in OOo 2.3 and 3.2, in Ubuntu, XP, Server 2003 and Windows 7. My Heisenbug detector is ticking. I tried to reduce the size of batches and restarting OOo after each one; still, a small percentage of the documents are messed up. Of course I'll write about this on the Ooo mailing lists, but in the meanwhile, I have a delivery and lost too much time already. Where do I go? Completely avoid the ODT format and go for another template system. Suggestions? Anything that takes a few seconds to run is way too slow. OOo takes around a second and it sums to 15 days of processing time. I had to write a program for clustering the jobs over several clients. Keep the format but go for another tool/program for the conversion. Which one? There are many apps in the shareware or commercial repositories for windows, but trying each one is a daunting task. Some are too slow, some cannot be run in batch without buying it first, some cannot work from command line, etc. Open source tools tend not to reinvent the wheel and often depend on openoffice. Converting to an intermediate .DOC format could help to avoid the OOo bug, but it would double the processing time and complicate a task that is already too hairy. Try to produce the PDFs twice and compare them, discarding the whole batch if there's something wrong. Although the documents look equal, I know of no way to compare the binary content. Restart OOo after processing each document. it would take a lot more time to produce them it would lower the percentage of the wrong files, and make it very hard to identify them. Go for ReportLab and recreate the pages programmatically. This is the approach I'm going to try in a few minutes. Learn to properly format bulleted lists Thanks a lot.

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• Web-Frameworks for Education Management Systems?

  - by Indebi

  So, I'm working on an idea and I'll go into a brief overview of that but my question is, What are some good web frameworks for this situation? I have some experience in the following languages: C# Python I have considerably more experience in C# than Python, however I am expecting to learn new things. My idea is this, a completely web-based community-oriented Education Management System that focuses on making students and teachers day-to-day lives easier. For students it will provide a centralized place for them to do homework, study for tests, and reinforce concepts learned previously in class. For teachers it will give them a centralized place to handle assignments, attendance, homework, tests, and all other major parts of classroom management. All of that, but in a community-oriented fashion. Everything a teacher does is shared and open to constructive criticism, allowing other teachers to use their assignments/tests and for students or other teachers to comment, rate and criticize their assignments. This encourages an environment of openness that will allow teacher's to focus on teaching and student's to focus on learning. And that community wouldn't be limited to one school or school-district, this system would be completely school-independent. Please note that I have no problem with hearing constructive criticism on this idea, however I would prefer if this post was more focused on my question. I have somewhat explored about the following options: Django ASP.NET Ruby on Rails Silverlight (1) I have Django installed and I played with it for a little bit, I really like how easy setting up databases are and how it handles the database completely for you. I don't really know how to use it very well and I don't quite understand the Model-View-Controller paradigm(?) for it yet but I haven't thought about it much. I also like the fact that it uses Python. (2) I don't really like Visual Studio for developing in ASP.NET, I hate the way the web-designer works and it just feels clunky and old. I like the server-side development part though. I don't like how expensive ASP.NET and overall Visual Studio is, even if I do get it for free for now using DreamSpark (3) I haven't been able to explore much with this, I could not get Rails (or maybe Ruby) properly installed. I first installed it within RadRails and that didn't work so I uninstalled RadRails and then installed the latest version of Ruby off the official Windows Installer and then installed Ruby on Rails through gem and even after all that it still didn't work, so I installed Netbeans and attempted to use it there but it still did not work (4) I like Silverlight in some extents, I've played with this one the most, it's very similar to WPF (which I've used the most) in a lot of ways but I don't like how database connectivity works, at least in comparison to Django. I also dislike how expensive everything with Microsoft is, even if I get it for free for now with DreamSpark. I would like to hear some suggestions from experienced web-developers as to what I should use and why, or at least what some good options are for my scenario Your help would be very appreciated

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