Search Results

Search found 21759 results on 871 pages for 'int 0'.

Page 502/871 | < Previous Page | 498 499 500 501 502 503 504 505 506 507 508 509  | Next Page >

  • Html.Editor() helper in ASP.NET MVC 3 does not work as expected with array in model

    - by SlimShaggy
    In my ASP.NET MVC 3 application I have classes like the following: public class Localization<T> { public int VersionID { get; set; } public T Value { get; set; } ... } public class Localizable<T> { public Localization<T>[] Name { get; set; } ... } Then, I have the following view: @model dynamic ... @for (int i = 0; i < VersionCount; i++) { ... @Html.Editor(string.Format("Name[{0}.Value", i)) ... } Now, when I display this view, passing a subclass of Localizable<string> as the model, the textboxes for the strings are rendered, but they are empty. If I replace @Html.Editor(string.Format("Name[{0}.Value", i)) with @InputExtensions.TextBox(Html, string.Format("Name[{0}].Value", i), Model.Name[i].Value), the textboxes are correctly filled with values from the model. However, using TextBox instead of Editor is not an option for me, because I want to use different editor templates for different types of T. So, what am I doing wrong, or is it a bug in MVC, and is there any workaround?

    Read the article

  • Why is android:transcriptMode="normal" not working properly?

    - by BCS
    I've been doing a lot of fiddling with an issue I've been having. What happens is each time an item gets added to my listview (adapter) I expect it to auto-scroll if I'm at the last item (which it will do to an extent); HOWEVER, if 3 or more items get added at once, it will not auto-scroll. Here is the XML of that listview: <ListView android:id="@android:id/list" android:layout_width="fill_parent" android:layout_height="0dip" android:layout_weight="1" android:transcriptMode="normal"/> I tried a workaround using a snippet I found here. My code is as follows: public void addChat(final String text, final String username) { this.runOnUiThread(new Runnable() { public void run() { globals.chatAdapter.add(DateFormat.format("hh:mmaa", Calendar.getInstance()).toString(), username, text); globals.chatAdapter.notifyDataSetChanged(); int lastP = getListView().getLastVisiblePosition(); int count = globals.chatAdapter.getCount() - 1; if (lastP == globals.chatAdapter.oldP || lastP == -1) { getListView().setSelection(count); } globals.chatAdapter.oldP = count; } }); } The problem with this is when a bunch of items come in at once, getListView().getLastVisiblePosition() will not update right away causing a setSelection() to never get called, and thus no auto-scroll. Any suggestions?

    Read the article

  • image list, listview,picturebox

    - by user548694
    I wanted to show my pics in picturebox. but also wanted to show a preview of pics. When user select a pic, it is shown in picbox but i have problem in resoulution. Here is my code private void openToolStripMenuItem_Click(object sender, EventArgs e) { ofd = new OpenFileDialog(); ofd.Title = "Open an Image File"; ofd.FileName = ""; ofd.Filter = "Image Files(*.jpg; *.jpeg; *.gif; *.bmp)|*.jpg; *.jpeg; *.gif; *.bmp"; if (ofd.ShowDialog() == DialogResult.OK) { DirectoryInfo dir = new DirectoryInfo(@"c:\pic"); foreach (FileInfo file in dir.GetFiles()) { this.imageList1.Images.Add(Image.FromFile(file.FullName)); } this.listView1.View = View.LargeIcon; this.imageList1.ImageSize = new Size(40, 40); this.listView1.LargeImageList = this.imageList1; for (int j=0; j < this.imageList1.Images.Count; j++) { ListViewItem item = new ListViewItem(); item.ImageIndex = j; listView1.Items.Add(item); ListViewItem item2 = new ListViewItem(); item2.SubItems.Add(j.ToString()); } private void listView1_SelectedIndexChanged(object sender, EventArgs e) { int i = this.listView1.FocusedItem.Index; this.PicBox1.Image = this.imageList1.Images[i]; } On click i see only image of resolution of (40,40) becuse i have set it this.imageList1.ImageSize = new Size(40, 40); and not orignal size. How can I have it. 2- I want to write also image names and index(image no) under each images. Its it possible. reagrsd,

    Read the article

  • displaying a physical webpage with frames in iframe

    - by ksa
    i have iframe in my webpage, i have done the coding part for browsing the folders and viewing files in iframe.each folder has a index.html.now i need to display the index.html in iframe.index.html page contains frames divided into 2,each from different sources.i tried to display a sample webpage without frames and it was a success,page with frames spoils the party. my code for getting the html file <% String path=request.getParameter("name"); File directory = new File(path); FileFilter fileFilter=new FileFilter() { @Override public boolean accept(File file) { return file.getName().endsWith("html"); } }; File[] files = directory.listFiles(fileFilter); for (int index = 0; index < files.length; index++) { String s= files[index].getName(); String s1=files[index].getAbsolutePath(); %> <a href="fileview?name=<%=s1%>" target="sss"><%=s%></a> <% } %> mycode for displaying the page in iframe. public void doGet(HttpServletRequest req,HttpServletResponse res) throws ServletException,IOException { res.setContentType("text/html"); PrintWriter out=res.getWriter(); String name=req.getParameter("name"); res.setHeader("Content-Disposition", "inline; filename=\""+name+"\""); java.io.FileInputStream fis=new java.io.FileInputStream(name); int i; while((i=fis.read())!=-1) { out.write(i); } fis.close(); out.close(); }

    Read the article

  • Error "initializer element is not constant" when trying to initialize variable with const

    - by tomlogic
    I get an error on line 6 (initialize my_foo to foo_init) of the following program and I'm not sure I understand why. typedef struct foo_t { int a, b, c; } foo_t; const foo_t foo_init = { 1, 2, 3 }; foo_t my_foo = foo_init; int main() { return 0; } Keep in mind this is a simplified version of a larger, multi-file project I'm working on. The goal was to have a single constant in the object file, that multiple files could use to initialize a state structure. Since it's an embedded target with limited resources and the struct isn't that small, I don't want multiple copies of the source. I'd prefer not to use: #define foo_init { 1, 2, 3 } I'm also trying to write portable code, so I need a solution that's valid C89 or C99. Does this have to do with the ORGs in an object file? That initialized variables go into one ORG and are initialized by copying the contents of a second ORG? Maybe I'll just need to change my tactic, and have an initializing function do all of the copies at startup. Unless there are other ideas out there?

    Read the article

  • Handle edittexts onKeyListener ?

    - by hungson175
    Hi everyone, I am creating login screen with 2 editTexts: etUsername and etPassword. On the etUsername, user should input the username and press Enter to go to the edit text etPassword, then he inputs the password, press Enter to login. Here are my current codes: etUsername.setOnKeyListener(new OnKeyListener() { @Override public boolean onKey(View v, int keyCode, KeyEvent event) { if ((keyCode == KeyEvent.KEYCODE_ENTER)) { etPassword.requestFocus(); return true; } else return false; } }); etPassword.setOnKeyListener(new OnKeyListener() { @Override public boolean onKey(View v, int keyCode, KeyEvent event) { if ((keyCode == KeyEvent.KEYCODE_ENTER)) { loginToServer(); return true; } else return false; } }); But when I input the username, and then press Enter – the program tries to log in to the server. In the debug mode, I saw that when I pressed Enter once (on the etUsername) then first: etUsername.onKey() is called and then etPassword.onKey() is also called ! Can anyone please tell me, how to implement what I want ? Thank you very much, Son

    Read the article

  • PHP & MySQL storing multiple values in a database.

    - by R.I.P.coalMINERS
    I'm basically a front end designer and new to PHP and MySQL but I want a user to be able to store multiple names and there meanings in a MySQL database table named names using PHP I will dynamically create form fields with JQuery every time a user clicks on a link so a user can enter 1 to 1,000,000 different names and there meanings which will be stored in a table called names. All I want to know is how can I store multiple names and there meanings in a database and then display them back to the user for them to edit or delete using PHP MySQL? I created the MySQL table already. CREATE TABLE names ( id INT UNSIGNED NOT NULL AUTO_INCREMENT, userID INT NOT NULL, name VARCHAR(255) NOT NULL, meaning VARCHAR(255) NOT NULL, PRIMARY KEY (id) ); Here is the HTML. <form method="post" action="index.php"> <ul> <li><label for="name">Name: </label><input type="text" name="name" id="name" /></li> <li><label for="meaning">Meaning: </label><input type="text" name="meaning" id="meaning" /></li> <li><input type="submit" name="submit" value="Save" /> <input type="hidden" name="submit" value="true" /></li> </ul> </form>

    Read the article

  • How to implement instance numbering?

    - by Joan Venge
    I don't know if the title is clear but basically I am trying to implement something like this: public class Effect { public int InternalId ... public void ResetName() ... } When ResetName is called, this will reset the name of the object to: "Effect " + someIndex; So if I have 5 instances of Effect, they will be renamed to: "Effect 1" "Effect 2" "Effect 3" ... So I have another method (ResetNames) in another manager/container type that calls ResetName for each instance. And right now I have to pass an integer to ResetName while keeping a counter myself inside ResetNames. But this feels not as clean and this prevents me from calling ResetName myself outside the manager class, which is valid. How to do this better/cleaner? As for the InternalId, it's just some id that stores the creation order for everything. So I can't just rely on these, because the numbers are large, like 32000, etc. EDIT: Container ResetNames code: int count = 1; var effects = this.Effects.OrderBy ( n => n.InternalId ); foreach ( Effect effect in effects ) { effect.ResetName ( count ); ++count; }

    Read the article

  • Need access to views on the OnSeekBarChangeListener (which is in an own class)

    - by sandkasten
    first of all I hope you understand my english because I'am not a native speaker. Okay, I'am new to android development and try following: For my app I need a SeekBar, so I create a Seekbar via XML and implement an OnSeekBarChangeListener. In the compay I work for its forbidden (because of the styleguid) to create something like this: seekbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() { @Override public void onProgressChanged(SeekBar arg0, int arg1, boolean arg2) { /// Do something } ... }); So I need to create a own class for the OnSeekBarChangeListener. So far no problem. public class SeekBarChangeListener extends SeekBar implements SeekBar.OnSeekBarChangeListener { public SeekBarChangeListener(Context context) { super(context); } public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) { } public void onStartTrackingTouch(SeekBar seekBar) { } public void onStopTrackingTouch(SeekBar seekBar) { /// Do something. Following Code wont work CheckBox RemeberUsername = (CheckBox)findViewById(R.id.RemeberUsername); /// Always gets NULL } } I need a way to get access to some controls. Normaly the findViewById works fine but not in this case (what I can totaly understand, because how should the listender know about the views?). Some good hints? Or is there no oter way like the first code snippet to get the controls? Hope someone can help me out.

    Read the article

  • Strange code behaviour?

    - by goldenmean
    Hi, I have a C code in which i have a structure declaration which has an array of int[576] declared in it. For some reason, i had to remove this array from the structure, So i replaced this array with a pointer as int *ptr; declared some global array of same type, somewhere else in the code, and initialized this pointer by assigning the global array to this pointer. So i did not have to change the way i was accessing this array, from other parts of my code. But it works fine/gives desired output when i have the array declared in the structure, but it gives junk output when i declare it as a pointer in the structure and assign a global array to this pointer, as a part of the pointer initialization. All this code is being run on MS-VC 6.0/Windows setup/Intel-x86. I tried below things: 1)Suspected structure padding/alignment but could not get any leads? If at all structure alignment could be a culprit how can i proceed to narrow it down and confirm it? 2) I have made sure that in both cases the array is initialized to some default values, say 0 before its first use, and its not being used before initialization. 3)I tried using global array as well as malloc based memory for this newly declared array. Same result, junk output. Am i missing something? How can i zero down the problem. Any pointers would be helpful. Thanks, -AD.

    Read the article

  • C# language questions

    - by Water Cooler v2
    1) What is int? Is it any different from the struct System.Int32? I understand that the former is a C# alias (typedef or #define equivalant) for the CLR type System.Int32. Is this understanding correct? 2) When we say: IComparable x = 10; Is that like saying: IComparable x = new System.Int32(); But we can't new a struct, right? or in C like syntax: struct System.In32 *x; x=>someThing = 10; 3) What is String with a capitalized S? I see in Reflector that it is the sealed String class, which, of course, is a reference type, unlike the System.Int32 above, which is a value type. What is string, with an uncapitalized s, though? Is that also the C# alias for this class? Why can I not see the alias definitions in Reflector? 4) Try to follow me down this subtle train of thought, if you please. We know that a storage location of a particular type can only access properties and members on its interface. That means: Person p = new Customer(); p.Name = "Water Cooler v2"; // legal because as Name is defined on Person. but // illegal without an explicit cast even though the backing // store is a Customer, the storage location is of type // Person, which doesn't support the member/method being // accessed/called. p.GetTotalValueOfOrdersMade(); Now, with that inference, consider this scenario: int i = 10; // obvious System.object defines no member to // store an integer value or any other value in. // So, my question really is, when the integer is // boxed, what is the *type* it is actually boxed to. // In other words, what is the type that forms the // backing store on the heap, for this operation? object x = i;

    Read the article

  • C++ const-reference semantics?

    - by Kristoffer
    Consider the sample application below. It demonstrates what I would call a flawed class design. #include <iostream> using namespace std; struct B { B() : m_value(1) {} long m_value; }; struct A { const B& GetB() const { return m_B; } void Foo(const B &b) { // assert(this != &b); m_B.m_value += b.m_value; m_B.m_value += b.m_value; } protected: B m_B; }; int main(int argc, char* argv[]) { A a; cout << "Original value: " << a.GetB().m_value << endl; cout << "Expected value: 3" << endl; a.Foo(a.GetB()); cout << "Actual value: " << a.GetB().m_value << endl; return 0; } Output: Original value: 1 Expected value: 3 Actual value: 4 Obviously, the programmer is fooled by the constness of b. By mistake b points to this, which yields the undesired behavior. My question: What const-rules should you follow when designing getters/setters? My suggestion: Never return a reference to a member variable if it can be set by reference through a member function. Hence, either return by value or pass parameters by value. (Modern compilers will optimize away the extra copy anyway.)

    Read the article

  • entering datas of php page to database

    - by Rahima farzana.S
    I have a php form with two text boxes and i want to enter the text box values into the database. I have created the table (with two columns namely webmeasurementsuite id and webmeasurements id) I used the following syntax for creating table: CREATE TABLE `radio` ( `webmeasurementsuite id` INT NOT NULL, `webmeasurements id` INT NOT NULL ); Utilising the tutorial in the following link, I wrote the php coding but unfortunately the datas are not getting entered into the database. I am getting an error in the insert sql syntax. I checked it but i am not able to trace out the error.Can anyone correct me? I got the coding from http://www.webune.com/forums/php-how-to-enter-data-into-database-with-php-scripts.html $sql = "INSERT INTO $db_table(webmeasurementsuite id,webmeasurements id) values ('".mysql_real_escape_string(stripslashes($_REQUEST['webmeasurementsuite id']))."','".mysql_real_escape_string(stripslashes($_REQUEST['webmeasurements id']))."')"; echo$sql; My error is as follows: INSERT INTO radio(webmeasurementsuite id,webmeasurements id) values ('','')ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'id,webmeasurements id) values ('','')' at line 1

    Read the article

  • What is the point of having a key_t if what will be the key to access shared memory is the return value of shmget()?

    - by devoured elysium
    When using shared memory, why should we care about creating a key key_t ftok(const char *path, int id); in the following bit of code? key_t key; int shmid; key = ftok("/home/beej/somefile3", 'R'); shmid = shmget(key, 1024, 0644 | IPC_CREAT); From what I've come to understand, what is needed to access a given shared memory is the shmid, not the key. Or am I wrong? If what we need is the shmid, what is the point in not just creating a random key every time? Edit @link text one can read: What about this key nonsense? How do we create one? Well, since the type key_t is actually just a long, you can use any number you want. But what if you hard-code the number and some other unrelated program hardcodes the same number but wants another queue? The solution is to use the ftok() function which generates a key from two arguments. Reading this, it gives me the impression that what one needs to attach to a shared-memory block is the key. But this isn't true, is it? Thanks

    Read the article

  • write a program that prompts the user to input five decimal numbers : C++

    - by user312309
    This is the question. write a program that prompts the user to input five decimal numbers. the program should then add the five decimal numbers, convert the sum to the nearest integer,m and print the result. This is what I've gotten so far: // p111n9.cpp : Defines the entry point for the console application. // #include <iostream> using namespace std; double a, b , c , d , e, f; int main(int argc, char* argv[]) { cout << "enter 5 decimals: " << endl; cin >> a >> b >> c >> d >> e; f = a + b + c + d + e; return 0; } Now I just need to convert the sum(f) to the nearest integer, m and print the result. How do I do this?

    Read the article

  • C# How can I get each column type and length and then use the lenght to padright to get the spaces a

    - by svon
    I have a console application that extracts data from a SQL table to a flat file. How can I get each column type and length and then use the lenght of each column to padright(length) to get the spaces at the end of each field. Here is what I have right now that does not include this functionality. Thanks { var destination = args[0]; var command = string.Format("Select * from {0}", Validator.Check(args[1])); var connectionstring = string.Format("Data Source={0}; Initial Catalog=dbname;Integrated Security=SSPI;", args[2]); var helper = new SqlHelper(command, CommandType.Text, connectionstring); using (StreamWriter writer = new StreamWriter(destination)) using (IDataReader reader = helper.ExecuteReader()) { while (reader.Read()) { Object[] values = new Object[reader.FieldCount]; int fieldCount = reader.GetValues(values); for (int i = 0; i < fieldCount; i++) writer.Write(values[i].ToString().PadRight(513)); writer.WriteLine(); } writer.Close(); }

    Read the article

  • QTime or QTimer wait for timeout

    - by user968243
    I'm writting a Qt application, and I have a four hour loop (in a seperate thread). In that four hour loop, I have to: do stuff with the serial port; wait a fixed period of time; do some more stuff with the serial port; wait an arbitrary amount of time. when 500ms have past, do more stuff; Go to 1. and repeat for four hours. Currently, my method of doing this is really bad, and crashes some computers. I have a whole bunch of code, but the following snippet basically shows the problem. The CPU goes to ~100% and eventually can crash the computer. void CRelayduinoUserControl::wait(int timeMS) { int curTime = loopTimer->elapsed(); while(loopTimer->elapsed() < curTime + timeMS); } I need to somehow wait for a particular amount of time to pass before continuing on with the program. Is there some function which will just wait for some arbitrary period of time while keeping all the timers going?

    Read the article

  • Sending Images over Sockets in C

    - by Takkun
    I'm trying to send an image file through a TCP socket in C, but the image isn't being reassembled correctly on the server side. I was wondering if anyone can point out the mistake? I know that the server is receiving the correct file size and it constructs a file of that size, but it isn't an image file. Client //Get Picture Size printf("Getting Picture Size\n"); FILE *picture; picture = fopen(argv[1], "r"); int size; fseek(picture, 0, SEEK_END); size = ftell(picture); //Send Picture Size printf("Sending Picture Size\n"); write(sock, &size, sizeof(size)); //Send Picture as Byte Array printf("Sending Picture as Byte Array\n"); char send_buffer[size]; while(!feof(picture)) { fread(send_buffer, 1, sizeof(send_buffer), picture); write(sock, send_buffer, sizeof(send_buffer)); bzero(send_buffer, sizeof(send_buffer)); } Server //Read Picture Size printf("Reading Picture Size\n"); int size; read(new_sock, &size, sizeof(1)); //Read Picture Byte Array printf("Reading Picture Byte Array\n"); char p_array[size]; read(new_sock, p_array, size); //Convert it Back into Picture printf("Converting Byte Array to Picture\n"); FILE *image; image = fopen("c1.png", "w"); fwrite(p_array, 1, sizeof(p_array), image); fclose(image);

    Read the article

  • Casting error in my form

    - by Siva
    I have a ComboBox in a DataGridView. However I get an error when I run it: Unable to cast object of type 'System.Windows.Forms.DataGridView' to type 'System.Windows.Forms.ComboBox'. What can I do to resolve this error? ComboBox comboBox; private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e) { if (e.Control is ComboBox) { comboBox = e.Control as ComboBox; if (dataGridView1.CurrentCell.ColumnIndex >= 0) { System.Diagnostics.Debug.WriteLine("Edit Control Showing"); comboBox.SelectedIndexChanged -= new EventHandler(comboBoxItems_SelectedIndexChanged); comboBox.SelectedIndexChanged += new EventHandler(comboBoxItems_SelectedIndexChanged); } } } void comboBoxItems_SelectedIndexChanged(object sender, EventArgs e) { try { int comboBoxSelectedIndex = ((ComboBox)sender).SelectedIndex; string comboboxSelectedValue = ((ComboBox)sender).SelectedText; int gridViewSelectedRow = dataGridView1.CurrentRow.Index; if (comboBoxSelectedIndex >= 0 && gridViewSelectedRow >= 0) { System.Diagnostics.Debug.WriteLine("ComboBox Index - " + comboBoxSelectedIndex); System.Diagnostics.Debug.WriteLine("GridView Index - " + gridViewSelectedRow); if (comboBox != null) { comboBox.SelectedIndexChanged -= new EventHandler(comboBoxItems_SelectedIndexChanged); } } } catch(Exception E) { } }

    Read the article

  • Without LIB And String file how can i write this code??

    - by muhammadlodhi
    #include<stdio.h> #include<conio.h> #include<stdlib.h> #include<string.h> struct Node; typedef struct Node * PtrToNode; struct Node { char element; PtrToNode Next; }; PtrToNode MakeEmpty(PtrToNode L) { L= new(Node); L->Next=NULL; return L; } void Push(PtrToNode L,char x) { PtrToNode S; S= new(Node); S->element=x; S->Next=L->Next; L->Next=S; } char Pop(PtrToNode L) { PtrToNode P; P=L->Next; char x=P->element; L->Next=P->Next; free(P); return x; } int main() { PtrToNode L; L= MakeEmpty(NULL); char Input[1000]; int i; printf("please enter your equation:"); scanf("%s",Input); for (i = 0;i<strlen(Input);i++) { if (Input[i]=='(') { Push(L,Input[i]); } if (Input[i]==')') { if (L->Next==NULL) { printf("incorrect"); return 0; } else Pop(L); } } if (L->Next==NULL) printf("correct"); else printf("incorrect"); getch(); return 0; }

    Read the article

  • std::thread and class constructor and destructor

    - by toeplitz
    When testing threads in C++11 I have created the following example: #include <iostream> #include <thread> class Foo { public: Foo(void) { std::cout << "Constructor called: " << this << std::endl; } ~Foo(void) { std::cout << "Destructor called: " << this << std::endl; } void operator()() const { std::cout << "Operatior called: " << this << std::endl; } }; void test_normal(void) { std::cout << "====> Standard example:" << std::endl; Foo f; } void test_thread(void) { std::cout << "====> Thread example:" << std::endl; Foo f; std::thread t(f); t.detach(); } int main(int argc, char **argv) { test_normal(); test_thread(); for(;;); } Which prints the following: Why is the destructor called 6 times for the thread? And why does the thread report different memory locations?

    Read the article

  • Hibernate Relationship Mapping/Speed up batch inserts

    - by manyxcxi
    I have 5 MySQL InnoDB tables: Test,InputInvoice,InputLine,OutputInvoice,OutputLine and each is mapped and functioning in Hibernate. I have played with using StatelessSession/Session, and JDBC batch size. I have removed any generator classes to let MySQL handle the id generation- but it is still performing quite slow. Each of those tables is represented in a java class, and mapped in hibernate accordingly. Currently when it comes time to write the data out, I loop through the objects and do a session.save(Object) or session.insert(Object) if I'm using StatelessSession. I also do a flush and clear (when using Session) when my line count reaches the max jdbc batch size (50). Would it be faster if I had these in a 'parent' class that held the objects and did a session.save(master) instead of each one? If I had them in a master/container class, how would I map that in hibernate to reflect the relationship? The container class wouldn't actually be a table of it's own, but a relationship all based on two indexes run_id (int) and line (int). Another direction would be: How do I get Hibernate to do a multi-row insert?

    Read the article

  • scala 2.8 CanBuildFrom

    - by oxbow_lakes
    Following on from another question I asked, I wanted to understand a bit more about the Scala method TraversableLike[A].map whose signature is as follows: def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That Notice a few things about this method: it takes a function turning each A in the traversable into a B it returns That and takes an implicit argument of type CanBuildFrom[Repr, B, That] I can call this as follows: > val s: Set[Int] = List("Paris", "London").map(_.length) s: Set[Int] Set(5,6) What I cannot quite grasp is how the fact that That is bound to B (i.e. it is some collection of B's) is being enforced by the compiler. The type parameters look to be independent in both the signature above and in the signature of the trait CanBuildFrom itself: trait CanBuildFrom[-From, -Elem, +To] How is the scala compiler ensuring that That cannot be forced into something which does not make sense? > val s: Set[String] = List("Paris", "London").map(_.length) //will not compile EDIT - this question of course boils down to: How does the compiler decide what implicit CanBuildFrom objects are in scope for the call?

    Read the article

  • Java iterative vs recursive

    - by user1389813
    Can anyone explain why the following recursive method is faster than the iterative one (Both are doing it string concatenation) ? Isn't the iterative approach suppose to beat up the recursive one ? plus each recursive call adds a new layer on top of the stack which can be very space inefficient. private static void string_concat(StringBuilder sb, int count){ if(count >= 9999) return; string_concat(sb.append(count), count+1); } public static void main(String [] arg){ long s = System.currentTimeMillis(); StringBuilder sb = new StringBuilder(); for(int i = 0; i < 9999; i++){ sb.append(i); } System.out.println(System.currentTimeMillis()-s); s = System.currentTimeMillis(); string_concat(new StringBuilder(),0); System.out.println(System.currentTimeMillis()-s); } I ran the program multiple time, and the recursive one always ends up 3-4 times faster than the iterative one. What could be the main reason there that is causing the iterative one slower ?

    Read the article

  • Java: GatheringByteChannel advantages?

    - by Jason S
    I'm wondering when the GatheringByteChannel's write methods (taking in an array of ByteBuffers) have advantages over the "regular" WritableByteChannel write methods. I tried a test where I could use the regular vs. the gathering write method on a FileChannel, with approx 400KB/sec total in ByteBuffers of between 23-27 bytes in length in both cases. Gathering writes used an array of 64. The regular method used up approx 12% of my CPU, and the gathering method used up approx 16% of my CPU (worse than the regular method!) This tells me it's NOT useful to use gathering writes on a FileChannel around this range of operating parameters. Why would this be the case, and when would you ever use GatheringByteChannel? (on network I/O?) Relevant differences here: public void log(Queue<Packet> packets) throws IOException { if (this.gather) { int Nbuf = 64; ByteBuffer[] bbufs = new ByteBuffer[Nbuf]; int i = 0; Packet p; while ((p = packets.poll()) != null) { bbufs[i++] = p.getBuffer(); if (i == Nbuf) { this.fc.write(bbufs); i = 0; } } if (i > 0) { this.fc.write(bbufs, 0, i); } } else { Packet p; while ((p = packets.poll()) != null) { this.fc.write(p.getBuffer()); } } }

    Read the article

< Previous Page | 498 499 500 501 502 503 504 505 506 507 508 509  | Next Page >