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  • What's the best way to explain parsing to a new programmer?

    - by Daisetsu
    I am a college student getting my Computer Science degree. A lot of my fellow students really haven't done a lot of programming. They've done their class assignments, but let's be honest here those questions don't really teach you how to program. I have had several other students ask me questions about how to parse things, and I'm never quite sure how to explain it to them. Is it best to start just going line by line looking for substrings, or just give them the more complicated lecture about using proper lexical analysis, etc. to create tokens, use BNF, and all of that other stuff? They never quite understand it when I try to explain it. What's the best approach to explain this without confusing them or discouraging them from actually trying.

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  • DataReader - hardcode ordinals?

    - by David Neale
    When returning data from a DataReader I would typically use the ordinal reference on the DataReader to grab the relevant column: if (dr.HasRows) Console.WriteLine(dr[0].ToString()); (OR dr.GetString(0); OR (string)dr[0];)... I have always done this because I was advised at an early stage that using dr["ColumnName"] or a more elegant way of indexing causes a performance hit. However, whilst everything is becoming increasingly strongly-typed I feel more uncomfortable with this. I'm also aware that the above does not check for DBNull. How should data be returned from a DataReader?

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  • What is the best way to add and order to Doctrine Nested Set Trees?

    - by murze
    What is the best way to add a sense of order in Doctrine Nested Sets? The documention contains several examples of how to get al the childeren of a specific node $category->getNode()->getSiblings() But how can I for example: change the position of the fourth sibling to the second position get only the second sibling add a sibling between the second and third child etc... Do I have to manually add and ordercolumn to the model to do these operations?

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  • Is it a good practice to suppress warnings?

    - by Chris Cooper
    Sometimes while writing Java in Eclipse, I write code that generates warnings. A common one is this, which I get when extending the Exception class: public class NumberDivideException extends Exception { public NumberDivideException() { super("Illegal complex number operation!"); } public NumberDivideException(String s) { super(s); } } // end NumberDivideException The warning: The serializable class NumberDivideException does not declare a static final serialVersionUID field of type long. I know this warning is caused by my failure to... well, it says right above. I could solve it by including the serialVersionUID, but this is a one hour tiny assignment for school; I don't plan on serializing it anytime soon... The other option, of course, is to let Eclipse add @SuppressWarnings("serial"). But every time my mouse hovers over the Suppress option, I feel a little guilty. For programming in general, is it a good habit to suppress warnings? (Also, as a side question, is adding a "generated" serialVersionUID like serialVersionUID = -1049317663306637382L; the proper way to add a serialVersionUID, or do I have to determine the number some other way?)

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  • How many files in a directory is too many?

    - by Kip
    Does it matter how many files I keep in a single directory? If so, how many files in a directory is too many, and what are the impacts of having too many files? (This is on a Linux server.) Background: I have a photo album website, and every image uploaded is renamed to an 8-hex-digit id (say, a58f375c.jpg). This is to avoid filename conflicts (if lots of "IMG0001.JPG" files are uploaded, for example). The original filename and any useful metadata is stored in a database. Right now, I have somewhere around 1500 files in the images directory. This makes listing the files in the directory (through FTP or SSH client) take a few seconds. But I can't see that it has any affect other than that. In particular, there doesn't seem to be any impact on how quickly an image file is served to the user. I've thought about reducing the number of images by making 16 subdirectories: 0-9 and a-f. Then I'd move the images into the subdirectories based on what the first hex digit of the filename was. But I'm not sure that there's any reason to do so except for the occasional listing of the directory through FTP/SSH.

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  • Convincing Management to use WCF

    - by Kyle Rozendo
    Hi All, I asked another question, stating that the I am unable to use WCF in a new Web Service project and have come to see that it seems to be the technology to use in regards to extensibility and security. My question is a simple one: How can I persuade management (and developers for that matter) to move over to using WCF as opposed to other web service technologies (ASMX/CFC)? They won't be concerned with a comparison between the types (especially with regard to ASMX), simply what there is to gain. Thanks for your time, Kyle

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  • Break nested loop in Django views.py with a function

    - by knuckfubuck
    I have a nested loop that I would like to break out of. After searching this site it seems the best practice is to put the nested loop into a function and use return to break out of it. Is it acceptable to have functions inside the views.py file that are not a view? What is the best practice for the location of this function? Here's the example code from inside my views.py @login_required def save_bookmark(request): if request.method == 'POST': form = BookmarkSaveForm(request.POST) if form.is_valid(): bookmark_list = Bookmark.objects.all() for bookmark in bookmark_list: for link in bookmark.link_set.all(): if link.url == form.cleaned_data['url']: # Do something. break else: # Do something else. else: form = BookmarkSaveForm() return render_to_response('save_bookmark_form.html', {'form': form})

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  • Exercise 26 of The Pragmatic Programmer

    - by _ande_turner_
    There is a code snippet presented in The Pragmatic Programmer on page 143 as: public class Colada { private Blender myBlender; private Vector myStuff; public Colada() { myBlender = new Blender(); myStuff = new Vector(); } private doSomething() { myBlender.addIngredients(myStuff.elements()); } } This obeys the Law of Demeter / Principle of Least Knowledge. Is it preferable to, and are there any caveats for, replacing it with the following, which utilises Dependency Injection? public class Colada throws IllegalArgumentException { private Blender myBlender; private Vector myStuff; public Colada(Blender blender, Vector stuff) { blender == null ? throw new IllegalArgumentException() : myBlender = blender; stuff == null ? throw new IllegalArgumentException() : myStuff = stuff; } public getInstance() { Blender blender = new Blender(); Vector stuff = new Vector(); return new Colada(blender, stuff); } private doSomething() { myBlender.addIngredients(myStuff.elements()); } }

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  • EXC_BAD_ACCESS when executing ABAddressBookSave !

    - by Horatiu Paraschiv
    Hi everybody, I'm trying to create a new contact and add it to the AddressBook but when I get to the ABAddressSave line of code I get EXC_BAD_ACCESS. I cannot see what am I doing wrong, I enabled NSZombie to check if this is a memory related error but it didn't spot any. Can anybody tell me what is wrong with this code? Thank you in advance! CFErrorRef error = NULL; ABAddressBookRef iPhoneAddressBook = ABAddressBookCreate(); ABRecordRef newRecord = ABPersonCreate(); ABRecordSetValue(newRecord, kABPersonFirstNameProperty, @"Xxxxxx", &error); ABRecordSetValue(newRecord, kABPersonURLProperty, @"Yyyyyy", &error); //Add phone numbers to record ABMutableMultiValueRef phones = ABMultiValueCreateMutable(kABMultiStringPropertyType); ABMultiValueAddValueAndLabel(phones, @"1-555-555-5555", kABWorkLabel, NULL); ABRecordSetValue(newRecord, kABPersonPhoneProperty, phones, &error); CFRelease(phones); //Add email address to record ABMutableMultiValueRef emails = ABMultiValueCreateMutable(kABMultiStringPropertyType); ABMultiValueAddValueAndLabel(emails, @"[email protected]", kABWorkLabel, NULL); ABRecordSetValue(newRecord, kABPersonEmailProperty, emails, &error); CFRelease(emails); ABMutableMultiValueRef multiAddress = ABMultiValueCreateMutable(kABMultiDictionaryPropertyType); NSMutableDictionary *addressDict = [[NSMutableDictionary alloc] init]; [addressDict setObject:@"xxx1" forKey:(NSString *)kABPersonAddressStreetKey]; [addressDict setObject:@"xxx2" forKey:(NSString *)kABPersonAddressCityKey]; [addressDict setObject:@"xxx3" forKey:(NSString *)kABPersonAddressStateKey]; [addressDict setObject:@"xxx4" forKey:(NSString *)kABPersonAddressZIPKey]; ABMultiValueAddValueAndLabel(multiAddress, addressDict, kABWorkLabel, NULL); ABRecordSetValue(newRecord, kABPersonAddressProperty, multiAddress, &error); CFRelease(multiAddress); [addressDict release]; ABAddressBookAddRecord(iPhoneAddressBook, newRecord, &error); ABAddressBookSave(iPhoneAddressBook, NULL); if(error != nil){ NSLog(@"Error creating contact:%@", error); }

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  • C# Static constructors design problem - need to specify parameter

    - by Neil Dobson
    I have a re-occurring design problem with certain classes which require one-off initialization with a parameter such as the name of an external resource such as a config file. For example, I have a corelib project which provides application-wide logging, configuration and general helper methods. This object could use a static constructor to initialize itself but it need access to a config file which it can't find itself. I can see a couple of solutions, but both of these don't seem quite right: 1) Use a constructor with a parameter. But then each object which requires corelib functionality should also know the name of the config file, so this has to be passed around the application. Also if I implemented corelib as a singleton I would also have to pass the config file as a parameter to the GetInstance method, which I believe is also not right. 2) Create a static property or method to pass through the config file or other external parameter. I have sort of used the latter method and created a Load method which initializes an inner class which it passes through the config file in the constructor. Then this inner class is exposed through a public property MyCoreLib. public static class CoreLib { private static MyCoreLib myCoreLib; public static void Load(string configFile) { myCoreLib = new MyCoreLib(configFile); } public static MyCoreLib MyCoreLib { get { return myCoreLib; } } public class MyCoreLib { private string configFile; public MyCoreLib(string configFile) { this.configFile = configFile; } public void DoSomething() { } } } I'm still not happy though. The inner class is not initialized until you call the load method, so that needs to be considered anywhere the MyCoreLib is accessed. Also there is nothing to stop someone calling the load method again. Any other patterns or ideas how to accomplish this?

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  • Does multiple cpp files correspond to multiple compilation units?

    - by Rahul
    Hello All, Suppose, we have a big Class. and we don't want to break it. In order to maintain code suppose we have created a multiple example1.cpp, example2.cpp, example3.cpp files for single example.h file for class cexample. Does this correspond to multiple compilations units? What is the best approach to handle such big classes? Any suggestions and comments are appreciated. Thank you, RAHUL

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  • What is your best-practice advice on implementing SQL stored procedures (in a C# winforms applicatio

    - by JYelton
    I have read these very good questions on SO about SQL stored procedures: When should you use stored procedures? and Are Stored Procedures more efficient, in general, than inline statements on modern RDBMS’s? I am a beginner on integrating .NET/SQL though I have used basic SQL functionality for more than a decade in other environments. It's time to advance with regards to organization and deployment. I am using .NET C# 3.5, Visual Studio 2008 and SQL Server 2008; though this question can be regarded as language- and database- agnostic, meaning that it could easily apply to other environments that use stored procedures and a relational database. Given that I have an application with inline SQL queries, and I am interested in converting to stored procedures for organizational and performance purposes, what are your recommendations for doing so? Here are some additional questions in my mind related to this subject that may help shape the answers: Should I create the stored procedures in SQL using SQL Management Studio and simply re-create the database when it is installed for a client? Am I better off creating all of the stored procedures in my application, inside of a database initialization method? It seems logical to assume that creating stored procedures must follow the creation of tables in a new installation. My database initialization method creates new tables and inserts some default data. My plan is to create stored procedures following that step, but I am beginning to think there might be a better way to set up a database from scratch (such as in the installer of the program). Thoughts on this are appreciated. I have a variety of queries throughout the application. Some queries are incredibly simple (SELECT id FROM table) and others are extremely long and complex, performing several joins and accepting approximately 80 parameters. Should I replace all queries with stored procedures, or only those that might benefit from doing so? Finally, as this topic obviously requires some research and education, can you recommend an article, book, or tutorial that covers the nuances of using stored procedures instead of direct statements?

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  • LINQ 2 SQL: Partial Classes

    - by Refracted Paladin
    I need to set the ConnectionString for my DataContext's based on an AppSetting. I am trying to do this by creating a Partial Class for each DataContext. The below is what I have so far and I am wondering if I am overlooking something? Specifically, am I dealing with my DataContext's correctly(disposing, staleness, etc)? Doing it this way will I have issues with Updates and Inserts? Is the file BLLAspnetdb.cs useful or neccessary in the least or should all of that be in the generated partial class AspnetdbDataContext file? In short, is this an acceptable structure or will this cause me issues as I elaborate it? dbml File Name = Aspnetdb.dbml Partial Class File Name = Aspnetdb.cs partial class AspnetdbDataContext { public static bool IsDisconnectedUser { get { return Convert.ToBoolean(ConfigurationManager.AppSettings["IsDisconnectedUser"]) == true; } } public static AspnetdbDataContext New { get { var cs = IsDisconnectedUser ? Settings.Default.Central_aspnetdbConnectionString : Settings.Default.aspnetdbConnectionString; return new AspnetdbDataContext(cs); } } } My Created File Name = BLLAspnetdb.cs public class BLLAspnetdb { public static IList WorkerList(Guid userID) { var DB = AspnetdbDataContext.New; var workers = from user in DB.tblDemographics where user.UserID == userID select new { user.FirstName, user.LastName, user.Phone }; IList theWorkers = workers.ToList(); return theWorkers; } public static String NurseName(Guid? userID) { var DB = AspnetdbDataContext.New; var nurseName = from demographic in DB.tblDemographics where demographic.UserID == userID select demographic.FirstName +" " + demographic.LastName; return nurseName.SingleOrDefault(); } public static String SocialWorkerName(Guid? userID) { var DB = AspnetdbDataContext.New; var swName = from demographic in DB.tblDemographics where demographic.UserID == userID select demographic.FirstName + " " + demographic.LastName; return swName.SingleOrDefault(); } } see this previous question and the accepted answer for background on how I got to here... switch-connectionstrings-between-local-and-remote-with-linq-to-sql

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  • When to use UserControl vs. Control in Silverlight?

    - by Dov
    I'm just getting my feet wet in Silverlight, and don't really understand the differences and pros/cons of creating a UserControl vs. creating a Control for the same task (as in when you right click on a selection in Expression Blend, for instance). It seems like selecting "Make Into Control" just creates a new template for the base type you specify, whereas creating a UserControl creates a whole new base class. Is that correct? In this particular instance, I'm creating a custom text box control that only takes numbers, and divides itself into 3 sections, storing 3 values into separate properties as pictured below. In this particular case, which would be best? Update (Additional Question): Why can't I use Template Binding with a UserControl, but I can with a Control? That's one reason I thought that making a UserControl might not be the right decision.

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  • Should using Eval carry the same stigma as GoTo?

    - by JustSmith
    It is taught in every computer science class and written in many books that programmers should not use GoTo. There is even an xkcd comic about it. My question is have we reached a point where the same thing can be said about Eval? Where GoTo is not conductive for program flow and readability, Eval is the same for debugging, and program execution, and design. Should using Eval have the same stigma as GoTo, and same consequences as in the xkcd comic?

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  • Accommodating hierarchical data in SQL Server 2005 database design

    - by Remnant
    Context I am fairly new to database design (=know the basics) and am grappling with how best to design my database for a project I am currently working on. In short, my database will keep a log of which employees have attended certain health and safety courses throughout the year. There are multiple types of course e.g. moving objects, fire safety, hygiene etc. In terms of my database design I need to accommodate the following: Each location can have multiple divisions Each division can have multiple departments Each department can have multiple functions Each function can have multiple job roles Each job role can have different course requirements Also note that the structure at each location may not be the same e.g. the departments within divisions are not the same across locations and the functions within departments may also differ. Edit - updated to better articulate problem Let's assume I am just looking at Location, Division and Department and I have my database as follows: LocationTable DivisionTable DepartmentTable LocationID(PK) DivisionID(PK) DepartmentID(PK) LocationName DivisionName DepartmentName There is a many-to-many relationship between Locations and Divisions and also between Departments and Divisions. Suppose I set up a 'Junction Table' as follows: Location_Division LocationID(FK) DivisionID(FK) Using Location_Division I could easily pull back the Divisions for any Location. However, suppose I want to pull back all departments for a given Division in a given Location. If I set up another 'Junction Table' for Division and Department then I can't see how I would differentiate Division by Location? Division_Department DivisionID(FK) DepartmentID(FK) Location_Division Division_Department LocationID DivisionID DivisionID DepartmentID 1 1 1 1 1 2 1 2 2 1 2 1 2 2 2 2 Do I need to expand the number of columns in my 'Junction Table' e.g. Location_Division_Department LocationID(FK) DivisionID(FK) DepartmentID(FK) Location_Division_Department LocationID DivisionID DepartmentID 1 1 1 1 1 2 1 1 3 2 1 1 2 1 2 2 1 3

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  • Using nullable types in C#

    - by Martin Brown
    I'm just interested in people's opinions. When using nullable types in C# what is the best practice way to test for null: bool isNull = (i == null); or bool isNull = !i.HasValue; Also when assigning to a non-null type is this: long? i = 1; long j = (long)i; better than: long? i = 1; long j = i.Value;

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  • Best practice for controlling a busy GUI

    - by MPelletier
    Suppose a GUI (C#, WinForms) that performs work and is busy for several seconds. It will still have buttons that need to remain accessible, labels that will change, progress bars, etc. I'm using this approach currently to change the GUI when busy: //Generic delegates private delegate void SetControlValue<T>(T newValue); //... public void SetStatusLabelMessage(string message) { if (StatusLabel.InvokeRequired) StatusLabel.BeginInvoke(new SetControlValue<string>(SetStatusLabelMessage, object[] { message }); else StatusLabel.Text = message; } I've been using this like it's going out of style, yet I'm not quite certain this is proper. Creating the delegate (and reusing it) makes the whole thing cleaner (for me, at least), but I must know that I'm not creating a monster...

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  • pointer as second argument instead of returning pointer?

    - by Tyler
    I noticed that it is a common idiom in C to accept an un-malloced pointer as a second argument instead of returning a pointer. Example: /*function prototype*/ void create_node(node_t* new_node, void* _val, int _type); /* implementation */ node_t* n; create_node(n, &someint, INT) Instead of /* function prototype */ node_t* create_node(void* _val, int _type) /* implementation */ node_t* n = create_node(&someint, INT) What are the advantages and/or disadvantages of both approaches? Thanks!

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