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• Splitting 25mb .txt file into smaller files using text delimiter

  - by user574141

  Regards, SO I am new to python and Perl. I have been trying to solve a simple problem and getting tied in knots with syntax. I hope someone has the time and patience to help. I have a 25mb file in ".txt" format which contains news-wire articles going back to 1970. Each news story is concatenated to the next, with only the "Copyright" statement to delimit. Each news story starts with "Item XX of XXX DOCUMENTS". There are certain metadata that are repeated throughout, I will use these for tagging later on. I wish to split this 25mb file into separate .txt files, each containing one news story (i.e. the text between "DOCUMENTS" and "Copyright", saving each with a different name (obviously). I am trying to 1 ) open the file... 2) iterate over lines in the file checking for the eof delimiter, and if it is not present writing the line to a list 3)write that list to a seperate small file. I'm having big problems with changing filenames using the counter, and how do I make Python start from where I left off, is the "seek" function appropriate? so far I have been trying this approach, completely unsuccessfully: myfile = open ("myfile.txt", 'r') filenumber = 0 for line in myfile.readline(): filenumber += 1 w=0 while myfile.readline() != '\s+DOCUMENTS\s*\n' ### read my line into a list mysmallfile()['w'] = [myfile.readline()] w += 1 output = open('C:\\Users\\dunner7\\Documents\###how do I change the filename each iteration???', 'w') output.writelines(mysmallfile) ###go back to start. Thank you for your time and patience. RD

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• SQL problem - select accross multiple tables (user groups)

  - by morpheous

  I have a db schema which looks something like this: create table user (id int, name varchar(32)); create table group (id int, name varchar(32)); create table group_member (foobar_id int, user_id int, flag int); I want to write a query that allows me to so the following: Given a valid user id (UID), fetch the ids of all users that are in the same group as the specified user id (UID) AND have group_member.flag=3. Rather than just have the SQL. I want to learn how to think like a Db programmer. As a coder, SQL is my weakest link (since I am far more comfortable with imperative languages than declarative ones) - but I want to change that. Anyway here are the steps I have identified as necessary to break down the task. I would be grateful if some SQL guru can demonstrate the simple SQL statements - i.e. atomic SQL statements, one for each of the identified subtasks below, and then finally, how I can combine those statements to make the ONE statement that implements the required functionality. Here goes (assume specified user_id [UID] = 1): //Subtask #1. Fetch list of all groups of which I am a member Select group.id from user inner join group_member where user.id=group_member.user_id and user.id=1 //Subtask #2 Fetch a list of all members who are members of the groups I am a member of (i.e. groups in subtask #1) Not sure about this ... select user.id from user, group_member gm1, group_member gm2, ... [Stuck] //Subtask #3 Get list of users that satisfy criteria group_member.flag=3 Select user.id from user inner join group_member where user.id=group_member.user_id and user.id=1 and group_member.flag=3 Once I have the SQL for subtask2, I'd then like to see how the complete SQL statement is built from these subtasks (you dont have to use the SQL in the subtask, it just a way of explaining the steps involved - also, my SQL may be incorrect/inefficient, if so, please feel free to correct it, and point out what was wrong with it). Thanks

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• Silverlight Binding - Binds when item is added but doesn't get updates.

  - by dw

  Hello, I'm sorta at a loss to why this doesn't work considering I got it from working code, just added a new level of code, but here's what I have. Basically, when I bind the ViewModel to a list, the binding picks up when Items are added to a collection. However, if an update occurs to the item that is bound, it doesn't get updated. Basically, I have an ObservableCollection that contains a custom class with a string value. When that string value gets updated I need it to update the List. Right now, when I debug, the list item does get updated correctly, but the UI doesn't reflect the change. If I set the bound item to a member variable and null it out then reset it to the right collection it will work, but not desired behavior. Here is a mockup of the code, hopefully someone can tell me where I am wrong. Also, I've tried implementing INofityPropertyChanged at every level in the code below. public class Class1 { public string ItemName; } public class Class2 { private Class2 _items; private Class2() //Singleton { _items = new ObservableCollection<Class1>(); } public ObservableCollection<Class1> Items { get { return _items; } internal set { _items = value; } } } public class Class3 { private Class2 _Class2Instnace; private Class3() { _Class2Instnace = Class2.Instance; } public ObservableCollection<Class1> Items2 { get {return _Class2Instnace.Items; } } } public class MyViewModel : INofityPropertyChanged { private Class3 _myClass3; private MyViewModel() { _myClass3 = new Class3(); } private BindingItems { get { return _myClass3.Items2; } // Binds when adding items but not when a Class1.ItemName gets updated. } }

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• Is there an efficient way in LINQ to use a contains match if and only if there is no exact match?

  - by Peter

  I have an application where I am taking a large number of 'product names' input by a user and retrieving some information about each product. The problem is, the user may input a partial name or even a wrong name, so I want to return the closest matches for further selection. Essentially if product name A exactly matches a record, return that, otherwise return any contains matches. Otherwise return null. I have done this with three separate statements, and I was wondering if there was a more efficient way to do this. I am using LINQ to EF, but I materialize the products to a list first for performance reasons. productNames is a List of product names (input by the user). products is a List of product 'records' var directMatches = (from s in productNames join p in products on s.ToLower() equals p.name.ToLower() into result from r in result.DefaultIfEmpty() select new {Key = s, Product = r}); var containsMatches = (from d in directMatches from p in products where d.Product == null && p.name.ToLower().Contains(d.Key) select new { d.Key, Product = p }); var matches = from d in directMatches join c in containsMatches on d.Key equals c.Key into result from r in result.DefaultIfEmpty() select new {d.Key, Product = d.Product ?? (r != null ? r.Product: null) };

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• ASP.NET enum dropdownlist validation

  - by Arun Kumar

  I have got a enum public enum TypeDesc { [Description("Please Specify")] PleaseSpecify, Auckland, Wellington, [Description("Palmerston North")] PalmerstonNorth, Christchurch } I am binding this enum to drop down list using the following code on page_Load protected void Page_Load(object sender, EventArgs e) { if (TypeDropDownList.Items.Count == 0) { foreach (TypeDesc newPatient in EnumToDropDown.EnumToList<TypeDesc>()) { TypeDropDownList.Items.Add(EnumToDropDown.GetEnumDescription(newPatient)); } } } public static string GetEnumDescription(Enum value) { FieldInfo fi = value.GetType().GetField(value.ToString()); DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false); if (attributes != null && attributes.Length > 0) return attributes[0].Description; else return value.ToString(); } public static IEnumerable<T> EnumToList<T>() { Type enumType = typeof(T); // Can't use generic type constraints on value types, // so have to do check like this if (enumType.BaseType != typeof(Enum)) throw new ArgumentException("T must be of type System.Enum"); Array enumValArray = Enum.GetValues(enumType); List<T> enumValList = new List<T>(enumValArray.Length); foreach (int val in enumValArray) { enumValList.Add((T)Enum.Parse(enumType, val.ToString())); } return enumValList; } and my aspx page use the following code to validate <asp:DropDownList ID="TypeDropDownList" runat="server" > </asp:DropDownList> <asp:RequiredFieldValidator ID="TypeRequiredValidator" runat="server" ControlToValidate="TypeDropDownList" ErrorMessage="Please Select a City" Text="<img src='Styles/images/Exclamation.gif' />" ValidationGroup="city"></asp:RequiredFieldValidator> But my validation is accepting "Please Specify" as city name. I want to stop user to submit if the city is not selected.

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• C# -Fluent interface implementation Help

  - by nettguy

  I am implementing the following piece of code using Fluent Interface design in C# 3.0. The code is working fine. public interface ITrainable { ITrainable AddSkill(string _skill); } public interface ISearchSkill { ISearchSkill SearchSkill(SoftwareEngineer emp,string[] _skills); } public abstract class Person { public Person(){} protected string Name { get; set; } } public class SoftwareEngineer:Person,ITrainable { protected internal List<string> skillSet { get; set; } public SoftwareEngineer() { } public SoftwareEngineer(string name) { Name=name; skillSet = new List<string>(); } public ITrainable AddSkill(string _skill) { skillSet.Add(_skill); return this; } } public class HRExecutive :Person,ISearchSkill { SoftwareEngineer _employee; public HRExecutive() { _employee=new SoftwareEngineer(); } public ISearchSkill SearchSkill(SoftwareEngineer _employee,string[] skills) { this._employee= _employee; foreach (string _skill in skills) { if (_employee.skillSet.Contains(_skill)) { Console.WriteLine(Name + " is trained on " + _skill); } else { Console.WriteLine(Name + " is not trained on " + _skill); } } return this; } } Execution SoftwareEngineer emp1 = new SoftwareEngineer("JonSkeet"); emp1.AddSkill("java").AddSkill("C#").AddSkill("F#"); HRExecutive hr = new HRExecutive(); hr.SearchSkill(emp1, new string[] { "java", "C#" }). SearchSkill(emp1, new string[] { "Oracle", "F#" }); Question : I don't want the skillSet of SoftwareEngineer being accessed by some XXX class.It could be accessed by limited classes.But protected internal List<string> skillSet { get; set; } is the only option (i think) i can declare in order to access the skillSet from HRExecutive.If i do so other XXX class can still access it. How to rewrite the code to prevent it?

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• MySQL LIMIT 1 but query 15 rows?

  - by Ian

  Basically what I'm trying to do is compare the ID's of rows against 15 results in MySQL, eliminating all but 1 (using NOT IN) and then pull that result. Now normally this would be fine by itself, however the order of the 15 rows I'm doing the SQL query for are constantly changing based on a ranking, so there is a possibility that between the time the ranking updates, and the ajax request (which I submit the ID's for NOT IN) more than just one ID has changed, which would of course bring back more than one row which I do not want. So in short, is there a way in which I can query 15 rows, but only return one? Without having to run two separate queries. Any help is appreciated, thank you. EXAMPLE: Say I have 7 items in my database, and I'm displaying 5 on the page to the user. These are what are being displayed to the user: Apple Orange Kiwi Banana Grape But in the database I also have Peach Blackberry Now what I want to do is if the user deletes an item from their list, it will add another item (based on a ranking they have) Now the issue is, in order to know what they have on their list at the moment I send the remaining items to the database (say they deleted Kiwi, I would send Apple, Orange, Banana, and Grape) So now I select the highest ranked 5 items from are remaining six items, make sure they are not the ones already displayed on the page, and then add the new one to list (either Peach or Blackberry) All good and well, except that if both peach and blackberry now outrank grape, then I will be returning two results instead of just one. Because it would've searched... Apple Orange Banana Peach Blackberry and excluded... Apple Orange Banana Grape Which leaves us with both Peach and Blackberry, instead of just Peach or Blackberry

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• How to print each object in a collection in a separate page in Silverlight

  - by Ash

  I would like to know if its possible to print each object in a collection in separate pages using Silverlight printing API. Suppose I have a class Label public class Label { public string Address { get; set; } public string Country { get; set; } public string Name { get; set; } public string Town { get; set; } } I can use print API and print like this. private PrintDocument pd; private void PrintButton_Click(object sender, RoutedEventArgs e) { pd.Print("Test Print"); } private void pd_PrintPage(object sender, PrintPageEventArgs e) { Label labelToPrint = new Label() { Name = "Fake Name", Address = "Fake Address", Country = "Fake Country", Town = "Town" }; var printpage = new LabelPrint(); printpage.DataContext = new LabelPrintViewModel(labelToPrint); e.PageVisual = printpage; } LabelPrint Xaml <StackPanel x:Name="LayoutRoot" VerticalAlignment="Center" HorizontalAlignment="Center"> <TextBlock Text="{Binding Name}" /> <TextBlock Text="{Binding Address}" /> <TextBlock Text="{Binding Town}" /> <TextBlock Text="{Binding Country}" /> </StackPanel> Now, say I've a collection of Label objects, List<Label> labels = new List<Label>() { labelToPrint, labelToPrint, labelToPrint, labelToPrint }; How can I print each object in the list in separate pages ? Thanks for any suggestions ..

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• iBatis how to solve a more complex N+1 problem

  - by Alvin

  I have a database that is similar to the following: create table Store(storeId) create table Staff(storeId_fk, staff_id, staffName) create table Item(storeId_fk, itme_id, itemName) The Store table is large. And I have create the following java bean public class Store { List<Staff> myStaff List<Item> myItem .... } public class Staff { ... } public class Item { ... } My question is how can I use iBatis's result map to EFFICIENTLY map from the tables to the java object? I tried: <resultMap id="storemap" class="my.example.Store"> <result property="myStaff" resultMap="staffMap"/> <result property="myItem" result="itemMap"/> </resultMap> (other maps omitted) But it's way too slow since the Store table is VERY VERY large. I tried to follow the example in Clinton's developer guide for the N+1 solution, but I cannot warp my mind around how to use the "groupBy" for an object with 2 list... Any help is appreciated!

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• iPhone app, navigationcontroller not functioning?

  - by dramaticlook

  I have 4 tabs in a tab bar. In one of the tabs i want to use a navigation, i.e. when i click an item from the list it should go to some details page about it. I have the list page where i have the navigation bar and the list of items. I can scroll them, but when I click any of them the selection animation happens, console logs the true row value, it even prints log instructions from constructor of the Details page but I can not see the Details page showing up. (btw Xcode 3.2.6 with iOS 4.3) - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSString *rowValue = [myStrings objectAtIndex:indexPath.row]; NSLog(rowValue); //[Utility setStr:rowValue]; [self.myTable deselectRowAtIndexPath:indexPath animated:TRUE]; //DETAILS PAGE HERE!!!! RestViewController * rest= [[RestViewController alloc] init]; rest.scoreLabel.text = rowValue; [self.navigationController pushViewController:rest animated:TRUE]; [rest release]; } Anybody having any idea? Thanks in advance!!!

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• Best implementation of Java Queue?

  - by Georges Oates Larsen

  I am working (In java) on a recursive image processing algorithm that recursively traverses the pixels of the image, outward from a center point. Unfortunately... That causes stack overflows, so I have decided to switch to a Queue-based algorithm. Now, this is all fine and dandy -- But considering the fact that its queue will be analyzing THOUSANDS of pixels in a very short amount of time, while constantly popping and pushing, WITHOUT maintaining a predictable state (It could be anywhere between length 100, and 20000); The queue implementation needs to have significantly fast popping and pushing abilities. A linked list seems attractive due to its ability to push elements unto its self without rearranging anything else in the list, but in order for it to be fast enough, it would need easy access to both its head, AND its tail (or second-to-last node if it were not doubly-linked). Sadly, though I cannot find any information related to the underlying implementation of linked lists in Java, so it's hard to say if a linked list is really the way to go... This brings me to my question... What would be the best implementation of the Queue interface in Java for what I intend to do? (I do not wish to edit or even access anything other than the head and tail of the queue -- I do not wish to do any sort of rearranging, or anything. On the flip side, I DO intend to do a lot of pushing and popping, and the queue will be changing size quite a bit, so preallocating would be inefficient)

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• NullPointerException when setting adapter

  - by Sorin Grecu

  I'm trying to get the filenames in a folder inside a listview(that listview is inside a layout of a ViewPager) but i'm getting a NullPointerException and i can't figure what's wrong. public void citire() { ListView lv1 = (ListView) findViewById(R.id.lv1); myList = new ArrayList<String>(); File directory = Environment.getExternalStorageDirectory(); file = new File(directory + "/InterSRL"); File list[] = file.listFiles(); for (int i = 0; i < list.length; i++) { myList.add(list[i].getName()); } ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, android.R.id.text1, myList); lv1.setAdapter(adapter); } I'm getting the error at lv1.setAdapter(adapter); 06-28 13:10:57.987: E/AndroidRuntime(30450): Caused by: java.lang.NullPointerException 06-28 13:10:57.987: E/AndroidRuntime(30450): at com.example.testlayout.Gestionare.citire(Gestionare.java:169) 06-28 13:10:57.987: E/AndroidRuntime(30450): at com.example.testlayout.Gestionare.onCreate(Gestionare.java:33) 06-28 13:10:57.987: E/AndroidRuntime(30450): at android.app.Activity.performCreate(Activity.java:5104) 06-28 13:10:57.987: E/AndroidRuntime(30450): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 06-28 13:10:57.987: E/AndroidRuntime(30450): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)

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• Rails: Can't set or update tag_list using a text field with acts_as_taggable_on

  - by Josh

  Hey everyone, I'm trying to add tagging to a rails photo gallery system I'm working on. It works from the back-end, but if I try to set or change it in the form view, it doesn't work. I added acts_as_taggable to the photo model and did the migrations. My gallery builder is programmed to add one tag automatically to each photo it creates. This works fine, just as if it were setting it for the console. However, I can't seem to set tags using a text_field in the photo form. Here's the code I added to my photo form: <p> <%= f.label :tag_list %><br /> <%= f.text_field :tag_list %> </p> Now, that's pretty trivial, and since :tag_list supports single-string comma-separated assignment (e.g. tag_list = "this, that, the other" #= ['this', 'that', 'the other']), I don't see why using a text field doesn't work. And to make even less sense, if a tag list has already been populated, the list will still show up in the text field when editing the photo. I just can't seem to commit any changes to the list. The documentation on their github page doesn't appear to give any information on how to set these values from the view. Any ideas? Oh, and I'm using the Rails 3 gem version.

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• jQuery: How to reverse sortable('serialize') arrays from last to first?

  - by Binyamin

  The discussion begins http://stackoverflow.com/questions/654535/jquery-what-to-do-with-the-list-that-sortableserialize-returns/2920760#2920760 How to reverse it from last to first, updateList.php?id[]=5&id[]=4&id[]=3&id[]=2&id[]=1&&action=update? <ul> <li id="oreder-5">5</li> <li id="oreder-4">4</li> <li id="oreder-3">3</li> <li id="oreder-2">2</li> <li id="oreder-1">1</li> <ul> My code: $(document).ready(function(){ order=[]; $('#list ul').children('li').each(function(idx, elm) { order.push(elm.id.split('-')[1]) }); $.post('updateList.php', {'order[]': order, action: 'update'}); function slideout(){ setTimeout(function(){ $("#response").slideUp("slow", function () {}); }, 2000); } $("#response").hide(); $(function() { $("#list ul").sortable({ opacity: 0.8, cursor: 'move', update: function() { var order = $(this).sortable("serialize") + '&action=update'; $.post("updateList.php", order, function(theResponse){ $("#response").html(theResponse); $("#response").slideDown('slow'); slideout(); }); }}); }); });

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• Managing libraries and imports in a programming language

  - by sub

  I've created an interpreter for a stupid programming language in C++ and the whole core structure is finished (Tokenizer, Parser, Interpreter including Symbol tables, core functions, etc.). Now I have a problem with creating and managing the function libraries for this interpreter (I'll explain what I mean with that later) So currently my core function handler is horrible: // Simplified version myLangResult SystemFunction( name, argc, argv ) { if ( name == "print" ) { if( argc < 1 ) { Error('blah'); } cout << argv[ 0 ]; } else if ( name == "input" ) { if( argc < 1 ) { Error('blah'); } string res; getline( cin, res ); SetVariable( argv[ 0 ], res ); } else if ( name == "exit ) { exit( 0 ); } And now think of each else if being 10 times more complicated and there being 25 more system functions. Unmaintainable, feels horrible, is horrible. So I thought: How to create some sort of libraries that contain all the functions and if they are imported initialize themselves and add their functions to the symbol table of the running interpreter. However this is the point where I don't really know how to go on. What I wanted to achieve is that there is e.g.: an (extern?) string library for my language, e.g.: string, and it is imported from within a program in that language, example: import string myString = "abcde" print string.at( myString, 2 ) # output: c My problems: How to separate the function libs from the core interpreter and load them? How to get all their functions into a list and add it to the symbol table when needed? What I was thinking to do: At the start of the interpreter, as all libraries are compiled with it, every single function calls something like RegisterFunction( string namespace, myLangResult (*functionPtr) ); which adds itself to a list. When import X is then called from within the language, the list built with RegisterFunction is then added to the symbol table. Disadvantages that spring to mind: All libraries are directly in the interpreter core, size grows and it will definitely slow it down.

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• Python: why does this code take forever (infinite loop?)

  - by Rosarch

  I'm developing an app in Google App Engine. One of my methods is taking never completing, which makes me think it's caught in an infinite loop. I've stared at it, but can't figure it out. Disclaimer: I'm using http://code.google.com/p/gaeunitlink text to run my tests. Perhaps it's acting oddly? This is the problematic function: def _traverseForwards(course, c_levels): ''' Looks forwards in the dependency graph ''' result = {'nodes': [], 'arcs': []} if c_levels == 0: return result model_arc_tails_with_course = set(_getListArcTailsWithCourse(course)) q_arc_heads = DependencyArcHead.all() for model_arc_head in q_arc_heads: for model_arc_tail in model_arc_tails_with_course: if model_arc_tail.key() in model_arc_head.tails: result['nodes'].append(model_arc_head.sink) result['arcs'].append(_makeArc(course, model_arc_head.sink)) # rec_result = _traverseForwards(model_arc_head.sink, c_levels - 1) # _extendResult(result, rec_result) return result Originally, I thought it might be a recursion error, but I commented out the recursion and the problem persists. If this function is called with c_levels = 0, it runs fine. The models it references: class Course(db.Model): dept_code = db.StringProperty() number = db.IntegerProperty() title = db.StringProperty() raw_pre_reqs = db.StringProperty(multiline=True) original_description = db.StringProperty() def getPreReqs(self): return pickle.loads(str(self.raw_pre_reqs)) def __repr__(self): return "%s %s: %s" % (self.dept_code, self.number, self.title) class DependencyArcTail(db.Model): ''' A list of courses that is a pre-req for something else ''' courses = db.ListProperty(db.Key) def equals(self, arcTail): for this_course in self.courses: if not (this_course in arcTail.courses): return False for other_course in arcTail.courses: if not (other_course in self.courses): return False return True class DependencyArcHead(db.Model): ''' Maintains a course, and a list of tails with that course as their sink ''' sink = db.ReferenceProperty() tails = db.ListProperty(db.Key) Utility functions it references: def _makeArc(source, sink): return {'source': source, 'sink': sink} def _getListArcTailsWithCourse(course): ''' returns a LIST, not SET there may be duplicate entries ''' q_arc_heads = DependencyArcHead.all() result = [] for arc_head in q_arc_heads: for key_arc_tail in arc_head.tails: model_arc_tail = db.get(key_arc_tail) if course.key() in model_arc_tail.courses: result.append(model_arc_tail) return result Am I missing something pretty obvious here, or is GAEUnit acting up?

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• ASP.NET MVC Dropdownlist retain the selected value in the browser after post

  - by MLabib

  I build a drop down list in my aspx page as following <%= Html.DropDownList("SelectedRole", new SelectList((IEnumerable)Model.roles, "RoleId", "RoleName", Model.SelectedRole), "")%> it works fine for first Get and the first default value is selected; then I select item from the drop down list and submit the form. the controller bind the values correctly, public ActionResult About([Bind] Roles r) { //r.SelectedRole = the selected value in the page. //Roles r = new Roles(); r.roles = new List<Role>(); r.roles.Add(new Role(1, "one")); r.roles.Add(new Role(2, "two")); r.roles.Add(new Role(3, "three")); r.roles.Add(new Role(4, "four")); r.SelectedRole = null; return View(r) } Then I nullify the selected item and return my view, but still the previous selected Item is selected (although I did nullify it) Any Idea if I am doing something wrong or it is a bug in MVC? I am using ASP.NET MVC 1 Thanks

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• How do I Order on common attribute of two models in the DB?

  - by Will

  If i have two tables Books, CDs with corresponding models. I want to display to the user a list of books and CDs. I also want to be able to sort this list on common attributes (release date, genre, price, etc.). I also have basic filtering on the common attributes. The list will be large so I will be using pagination in manage the load. items = [] items << CD.all(:limit => 20, :page => params[:page], :order => "genre ASC") items << Book.all(:limit => 20, :page => params[:page], :order => "genre ASC") re_sort(items,"genre ASC") Right now I am doing two queries concatenating them and then sorting them. This is very inefficient. Also this breaks down when I use paging and filtering. If I am on page 2 of how do I know what page of each table individual table I am really on? There is no way to determine this information without getting all items from each table. I have though that if I create a new Class called items that has a one to one relationship with either a Book or CD and do something like Item.all(:limit => 20, :page => params[:page], :include => [:books, :cds], :order => "genre ASC") However this gives back an ambiguous error. So can only be refined as Item.all(:limit => 20, :page => params[:page], :include => [:books, :cds], :order => "books.genre ASC") And does not interleave the books and CDs in a way that I want. Any suggestions.

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• How to create a generic method in C# that's all applicable to many types - ints, strings, doubles et

  - by satyajit

  Let's I have a method to remove duplicates in an integer Array public int[] RemoveDuplicates(int[] elems) { HashSet<int> uniques = new HashSet<int>(); foreach (int item in elems) uniques.Add(item); elems = new int[uniques.Count]; int cnt = 0; foreach (var item in uniques) elems[cnt++] = item; return elems; } How can I make this generic such that now it accepts a string array and remove duplicates in it? How about a double array? I know I am probably mixing things here in between primitive and value types. For your reference the following code won't compile public List<T> RemoveDuplicates(List<T> elems) { HashSet<T> uniques = new HashSet<T>(); foreach (var item in elems) uniques.Add(item); elems = new List<T>(); int cnt = 0; foreach (var item in uniques) elems[cnt++] = item; return elems; } The reason is that all generic types should be closed at run time. Thanks for you comments

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• Can Haskell's monads be thought of as using and returning a hidden state parameter?

  - by AJM

  I don't understand the exact algebra and theory behind Haskell's monads. However, when I think about functional programming in general I get the impression that state would be modelled by taking an initial state and generating a copy of it to represent the next state. This is like when one list is appended to another; neither list gets modified, but a third list is created and returned. Is it therefore valid to think of monadic operations as implicitly taking an initial state object as a parameter and implicitly returning a final state object? These state objects would be hidden so that the programmer doesn't have to worry about them and to control how they gets accessed. So, the programmer would not try to copy the object representing the IO stream as it was ten minutes ago. In other words, if we have this code: main = do putStrLn "Enter your name:" name <- getLine putStrLn ( "Hello " ++ name ) ...is it OK to think of the IO monad and the "do" syntax as representing this style of code? putStrLn :: IOState -> String -> IOState getLine :: IOState -> (IOState, String) main :: IOState -> IOState -- main returns an IOState we can call "state3" main state0 = putStrLn state2 ("Hello " ++ name) where (state2, name) = getLine state1 state1 = putStrLn state0 "Enter your name:"

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• Java: any problems/negative sides of keeping SoftReference to ArrayList in HttpSession?

  - by westla7

  My code is doing the following (just as an example, and the reason that I specify package path to java.lang.ref.SoftReference is to note that it's not my own implementaiton :-): ... List<String> someData = new ArrayList<String>(); someData.add("Value1"); someData.add("Value2"); ... java.lang.ref.SoftReference softRef = new SoftReference(someData); ... HttpSession session = request.getSession(true); session.setAttribute("mySoftRefData", softRef); ... and later: ... java.lang.ref.SoftReference softRef = session.getAttribute("mySoftRefData"); if (softRef != null && softRef.get() != null) { List<String> someData = (List<String>)softRef.get(); // do something with it. } ... Any disadvantages? Which I do not see? Thank you!

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• return ArrayList from spring controller for ajax call and render in second dropdown

  - by user1708125

  I've a spring bean with 3 Maps all of which are to be populated incrementally. First map is an item category list, second map is a product list and third map is a hobby for item type list All the maps are mapped to and on the JSP. When the page is loaded only the first map is populated on the onchange event of first map, I need to populate the second map in the bean and similarly on the onchange event of second map, I need to populate the third map in the bean. Is there a way to do this using Ajax?? I need some code samples to how to render JSON response in second and third dropdown. Clarification: @Donal: I have a simple JSP page with 3 dropdowns corresponding to 3 maps stored in my commandBean. So when the page loads for the first time only the first map and hence the first dropdown is populated. Now whenever the user selects anything out of the first dropdown, I need to send the same commandbean back with the values of the first dropdown and get the values for the second map and hence the second dropdown and so forth for the 3rd dropdown as well. For each dropdown I 've got 3 maps and 3 variables for storing the selected values. Now I want to understand if this is possible using Ajax. I hope this clarifies whatever you need to know. Thanx

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• Load iframe in html, only with jquery

  - by phpExe

  In this jquery code: $(document).ready(function(){ $list = $(".channeList li"); $list.click(function(){ var $this = $(this); var $mainDesc = $(".ply"); var iframe = $("a", $this).attr("rel"); $("iframe", $mainDesc).attr("src", iframe); } ); } ); There is a list o channels in left that iframe loads from a rel's. I want to load first iframe in <div class="ply"></div> In html, I dont want insert the first item. Can we do this without load first item in html and do this only with jquery? The php function channel() { if (is_numeric($_GET['kanalID'])) { $kanalID = $_GET['kanalID']; } if ($_GET['kanalID'] == "") { $kanalID = 1;} $channel = '<ul class="channeList">'; foreach ($tv as $id => $kanal) { $class = $kanalID == $id ? $class = "currentt": ''; $channel .= '<li> <a href="#" rel="http://mysite.com/index.php?id='.$id.'&w=500&h=320" >'.$kanal.'</a></li>'; } $channel .= '</ul>'; $channel .= '<div class="ply"><iframe frameborder=0 width="500" height="320"></iframe></div>'; return $channel; } Thanks in advance

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• Is is possible to do an end-run around generics covariance in C# < 4 in this hypothetical situation?

  - by John Feminella

  Suppose I have a small inheritance hierarchy of Animals: public interface IAnimal { string Speak(); } public class Animal : IAnimal { public Animal() {} public string Speak() { return "[Animal] Growl!"; } } public class Ape : IAnimal { public string Speak() { return "[Ape] Rawrrrrrrr!"; } } public class Bat : IAnimal { public string Speak() { return "[Bat] Screeeeeee!"; } } Next, here's an interface offering a way to turn strings into IAnimals. public interface ITransmogrifier<T> where T : IAnimal { T Transmogrify(string s); } And finally, here's one strategy for doing that: public class Transmogrifier<T> : ITransmogrifier<T> where T : IAnimal, new() { public T Transmogrify(string s) { T t = default(T); if (typeof(T).Name == s) t = new T(); return t; } } Now, the question. Is it possible to replace the sections marked [1], [2], and [3] such that this program will compile and run correctly? If you can't do it without touching parts other than [1], [2], and [3], can you still get an IAnimal out of each instance of a Transmogrifier in a collection containing arbitrary implementations of an IAnimal? Can you even form such a collection to begin with? static void Main(string[] args) { var t = new Transmogrifier<Ape>(); Ape a = t.Transmogrify("Ape"); Console.WriteLine(a.Speak()); // Works! // But can we make an arbitrary collection of such animals? var list = new List<Transmogrifier< [1] >>() { // [2] }; // And how about we call Transmogrify() on each one? foreach (/* [3] */ transmogrifier in list) { IAnimal ia = transmogrifier.Transmogrify("Bat"); } } }

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• ASP.Net event only being raised every other time?

  - by eftpotrm

  I have an ASP.Net web user control which represents a single entry in a list. To allow users to reorder the items, each item has buttons to move the item up or down the list. Clicking on one of these raises an event to the parent page, which then shuffles the items in the placeholder control. Code fragments from the list entry: Public Event UpClicked As System.EventHandler Protected Sub btnUp_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnUp.Click RaiseEvent UpClicked(Me, New EventArgs()) End Sub And the parent container: rem (within the code to add an individual item to the placeholder) AddHandler l_oItem.UpClicked, AddressOf UpClicked Protected Sub UpClicked(ByVal sender As Object, ByVal e As EventArgs) MoveItem(DirectCast(sender, ScriptListItem), -1) End Sub It originally looked in testing like every other time the value for sender (verified by its properties) that reaches UpClicked is of an adjacent ListItem, not the one I've just clicked on - the first click is always wrong, then the second for the correct control. At present, testing appears to show that the button's click event is just being ignored every other time through. Breakpoints on the click events within the control simply aren't being hit, though the events are definitely being established. Why?

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