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  • Classes and Objects in C++

    - by anurag18294
    class anurag { private: int rollno; char name[50]; int marks; float percen; void percentage(int num) { percen=(num/500)*100; } public: void getdata(void) { cout<<"\n\nEnter the name of the student:"; gets(name); cout<<"\n\nEnter the roll no: and the marks:"; cin>>rollno>>marks; percentage(marks); } void display(void) { cout<<"\n\nThe name of the student is:"; cout.write(name,50); cout<<"\n\nThe roll no: of the student is:"; cout<<rollno; cout<<"\n\n The marks obtained is:"<<marks; cout<<"\n\nThe percentage is:"<<percen; }}; void main() { clrscr(); anurag F; F.getdata(); F.display(); getch(); } why the following code is not giving the desired output?

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  • Why is joining two vectors simply not working?

    - by Jim
    I have two vectors of MyObj structs. MyObj is defined as follows: struct MyObj { float x, y; unsigned int data[8]; unsigned int tmp[1]; MyObj(const MyObj &m) { x = m.x; y = m.y; tmp[0] = 0; for (int i = 0; i < 8; ++i) { data[i] = m.data[i]; } } }; I then have two vectors... vector<MyObj> v1; vector<MyObj> v2; // both get data eventually. v1.insert(v1.end(), v2.begin(), v2.end()); v2 has 3535004 elements in my experiment. v1 is similarly sized. I've also tried building a new vector and just using .push_back to build it from both vectors. Essentially, when I try to merge the two vectors I just get an error from visual studio saying "Debug error! R6010, abort() has been called". Very non-useful... So my question is: what could be causing this error, and how can I solve it? Thank you

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  • Accessing derived class members with a base class pointer

    - by LRB
    I am making a simple console game in C++ I would like to know if I can access members from the 'entPlayer' class while using a pointer that is pointing to the base class ( 'Entity' ): class Entity { public: void setId(int id) { Id = id; } int getId() { return Id; } protected: int Id; }; class entPlayer : public Entity { string Name; public: entPlayer() { Name = ""; Id = 0; } void setName(string name) { Name = name; } string getName() { return Name; } }; Entity *createEntity(string Type) { Entity *Ent = NULL; if (Type == "player") { Ent = new entPlayer; } return Ent; } void main() { Entity *ply = createEntity("player"); ply->setName("Test"); ply->setId(1); cout << ply->getName() << endl; cout << ply->getId() << endl; delete ply; } How would I be able to call ply-setName etc? OR If it's not possible that way, what would be a better way?

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  • MySql stored procedure not found in PHP

    - by kaupov
    Hello, I have a trouble with MySql stored procedure that calls itself recursively using PHP (CakePHP). Calling it I receive following error: SQL Error: 1305: FUNCTION dbname.GetAdvertCounts does not exist The procedure itself is following: delimiter // DROP PROCEDURE IF EXISTS GetAdvertCounts// CREATE PROCEDURE GetAdvertCounts(IN category_id INT) BEGIN DECLARE no_more_sub_categories, advert_count INT DEFAULT 0; DECLARE sub_cat_id INT; DECLARE curr_sub_category CURSOR FOR SELECT id FROM categories WHERE parent_id = category_id; DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_sub_categories = 1; SELECT COUNT(*) INTO advert_count FROM adverts WHERE category_id = category_id; OPEN curr_sub_category; FETCH curr_sub_category INTO sub_cat_id; REPEAT SELECT advert_count + GetAdvertCounts(sub_cat_id) INTO advert_count; FETCH curr_sub_category INTO sub_cat_id; UNTIL no_more_sub_categories = 1 END REPEAT; CLOSE curr_sub_category; SELECT advert_count; END // delimiter ; If I remove or comment out the recursive call, the procedure is working. Any idea what I'm missing here? The categories are 2 level deep.

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  • C++ Template problem adding two data types

    - by Sara
    I have a template class with an overloaded + operator. This is working fine when I am adding two ints or two doubles. How do I get it to add and int and a double and return the double? template <class T> class TemplateTest { private: T x; public: TemplateTest<T> operator+(const TemplateTest<T>& t1)const { return TemplateTest<T>(x + t1.x); } } in my main function i have void main() { TemplateTest intTt1 = TemplateTest<int>(2); TemplateTest intTt2 = TemplateTest<int>(4); TemplateTest doubleTt1 = TemplateTest<double>(2.1d); TemplateTest doubleTt2 = TemplateTest<double>(2.5d); std::cout << intTt1 + intTt2 << /n; std::cout << doubleTt1 + doubleTt2 << /n; } I want to be able to also do this std::cout << doubleTt1 + intTt2 << /n;

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  • Strange compiler complaint when using similar code

    - by Jason
    For a project, I have to ask the user for a file name, and I'm reading it in character by character using getchar. From the main, I call the function char *coursename= introPrint(); //start off to print the usage directions and get the first bit of input. That function is defined as char *introPrint(){ int size= 20; int c; int length=0; char buffer[size]; //instructions printout, cut for brevity //get coursename from user and return it while ( (c=getchar()) != EOF && (c != '\n') ){ buffer[length++]= c; if (length==size-1) break; } buffer[length]=0; return buffer; } This is basically identical code I wrote to ask the user for input, replace the character echo with asterisks, then print out the results. Here, though, I'm getting a function returns address of local variable warning for the return statement. So why am I getting no warnings from the other program, but trigger one for this code?

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  • power and modulo on the fly for big numbers

    - by user unknown
    I raise some basis b to the power p and take the modulo m of that. Let's assume b=55170 or 55172 and m=3043839241 (which happens to be the square of 55171). The linux-calculator bc gives the results (we need this for control): echo "p=5606;b=55171;m=b*b;((b-1)^p)%m;((b+1)^p)%m" | bc 2734550616 309288627 Now calculating 55170^5606 gives a somewhat large number, but since I have to do a modulooperation, I can circumvent the usage of BigInt, I thought, because of: (a*b) % c == ((a%c) * (b%c))%c i.e. (9*7) % 5 == ((9%5) * (7%5))%5 => 63 % 5 == (4 * 2) %5 => 3 == 8 % 5 ... and a^d = a^(b+c) = a^b * a^c, therefore I can divide b+c by 2, which gives, for even or odd ds d/2 and d-(d/2), so for 8^5 I can calculate 8^2 * 8^3. So my (defective) method, which always cut's off the divisor on the fly looks like that: def powMod (b: Long, pot: Int, mod: Long) : Long = { if (pot == 1) b % mod else { val pot2 = pot/2 val pm1 = powMod (b, pot, mod) val pm2 = powMod (b, pot-pot2, mod) (pm1 * pm2) % mod } } and feeded with some values, powMod (55170, 5606, 3043839241L) res2: Long = 1885539617 powMod (55172, 5606, 3043839241L) res4: Long = 309288627 As we can see, the second result is exactly the same as the one above, but the first one looks quiet different. I'm doing a lot of such calculations, and they seem to be accurate as long as they stay in the range of Int, but I can't see any error. Using a BigInt works as well, but is way too slow: def calc2 (n: Int, pri: Long) = { val p: BigInt = pri val p3 = p * p val p1 = (p-1).pow (n) % (p3) val p2 = (p+1).pow (n) % (p3) print ("p1: " + p1 + " p2: " + p2) } calc2 (5606, 55171) p1: 2734550616 p2: 309288627 (same result as with bc) Can somebody see the error in powMod?

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  • What is a simple way to add a timer to a method

    - by John
    The following is in C#. I'm trying to do something very simple (I think). I have a method that loads an XML document XDocument doc = XDocument.Load(uri); , but I don't want to tie up pc resources if there are issues (connectivity, document size, etc.). So I'd like to be able to add a timeout variable that will cut the method off after a given number of seconds. I'm a newbie when it comes to asynchronous programming and find it confusing that there are so many examples written so many different ways . . . and none of them appear simple. I'd like a simple solution, if possible. Here's my thoughts so far on possible solution paths: 1) A method that wraps the existing load public XDocument LoadXDocument(string uri, int timeout){ //code } 2) A wrapper, but as an extension method XDocument doc = XDocument.LoadWithTimeout(string uri, int timeout); 3) A generic extension method. Object obj = SomeStaticClass.LoadWithTimeout(??? method, int timeout); 3), on its face seems really nice, because it would mean being able to generically add timeouts to many different method calls and not specifically tied to one type of object, but I suspect that it is either i)impossible or ii) very difficult. Please assist. Thanks.

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  • "Abstract static" method - how?

    - by polyglot
    There are already several SO questions on why there is not abstract static method/field as such, but I'm wondering about how one would go about implementing the following psuedo-code: class Animal { abstract static int getNumberOfLegs(); // not possible } class Chicken inherits Animal { static int getNumberOfLegs() { return 2; } class Dog inherits Animal { static int getNumberOfLegs() { return 4; } Here is the problem: Assuming that I want make sure that every class that inherits Animal to contain getNumberOfLegs() method (i.e. almost like an interface, except I do want the abstract class to implement several methods that are common to all child classes, hence pure interface does not work here). getNumberOfLegs() obviously should be a static method (assuming that in a perfect world we dont' have crippled chicken and dogs so getNumberOfLegs is not instance-dependent). Without an "abstract static" method/field, one can either leave the method out from Animal class, then there is the risk that some child class do not have that method. Or one can make getNumberOfLegs an instance method, but then one would have to instantiate a class to find out how many legs that animal has - even though it is not necessary. How do one usually go about implementing this situation?

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  • Help! I'm a Haskell Newbie

    - by Darknight
    I've only just dipped my toe in the world of Haskell as part of my journey of programming enlightenment (moving on from, procedural to OOP to concurrent to now functional). I've been trying an online Haskell Evaluator. However I'm now stuck on a problem: Create a simple function that gives the total sum of an array of numbers. In a procedural language this for me is easy enough (using recursion) (c#) : private int sum(ArrayList x, int i) { if (!(x.Count < i + 1)) { int t = 0; t = x.Item(i); t = sum(x, i + 1) + t; return t; } } All very fine however my failed attempt at Haskell was thus: let sum x = x+sum in map sum [1..10] this resulted in the following error (from that above mentioned website): Occurs check: cannot construct the infinite type: a = a -> t Please bear in mind I've only used Haskell for the last 30 minutes! I'm not looking simply for an answer but a more explanation of it. Thanks in advanced.

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  • row number over text column sort

    - by Marty Trenouth
    I'm having problems with dynamic sorting using ROW Number in SQL Server. I have it working but it's throwing errors on non numeric fields. What do I need to change to get sorts with Alpha Working??? ID Description 5 Test 6 Desert 3 A evil Ive got a Sql Prodcedure CREATE PROCEDURE [CRUDS].[MyTable_Search] -- Add the parameters for the stored procedure here -- Full Parameter List @ID int = NULL, @Description nvarchar(256) = NULL, @StartIndex int = 0, @Count int = null, @Order varchar(128) = 'ID asc' AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; -- Insert statements for procedure here Select * from ( Select ROW_NUMBER() OVER (Order By case when @Order = 'ID asc' then [TableName].ID when @Order = 'Description asc' then [TableName].Description end asc, case when @Order = 'ID desc' then [TableName].ID when @Order = 'Description desc' then [TableName].Description end desc ) as row, [TableName].* from [TableName] where (@ID IS NULL OR [TableName].ID = @ID) AND (@Description IS NULL OR [TableName].Description = @Description) ) as a where row > @StartIndex and (@Count is null or row <= @StartIndex + @Count) order by case when @Order = 'ID asc' then a.ID when @Order = 'Description asc' then a.Description end asc, case when @Order = 'ID desc' then a.ID when @Order = 'Description desc' then a.Description end desc END

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  • novice needing help on shuffeling an array

    - by steffen Myklebust
    Please help a TOTAL beginner.! I found this post: http://stackoverflow.com/questions/56648/whats-the-best-way-to-shuffle-an-nsmutablearray And as i try to deploy this in my own code, I cant get it working... :-( Can anyone help me to resolve this code? To me it looks like the shuffle function is not called..? here is my code: // // shuffle2ViewController.h // shuffle2 #import @interface shuffle2ViewController : UIViewController { NSMutableArray *puzzles; int *randomSort; } - (void)shuffle; @end //============================= // shuffle2ViewController.m ´#import "shuffle2ViewController.h" @implementation shuffle2ViewController (void)viewDidLoad { [super viewDidLoad]; NSMutableArray *puzzles = [NSMutableArray arrayWithObjects:@"1",@"2",@"3", @"4",@"5",@"6",@"7",@"8",@"9", @"10",@"11",@"12", nil]; // Call the shuffle function [self shuffle]; // print to log int i; NSLog(@"NEW OLD"); NSLog(@"================="); for (i = 0; i < 12; ++i) NSLog(@" %2i %@", i + 1, [puzzles objectAtIndex:i]); } int randomSort(id obj1, id obj2, void *context ) { // returns random number -1 0 1 return (random()%3 - 1); } (void)shuffle { // call custom sort function [puzzles sortUsingFunction:randomSort context:nil]; } Giving this result: NEW OLD ================= 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12

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  • How to customize file dialog in wpf

    - by ManjuAnoop
    In Windows7 I am using a customized Open File Dialog( WPF application). My Open File dialog is derived from Microsoft.Win32.CommonDialog. The dialog have old look, how to change this to new look (windows7 file dialog look(Explorer style)). Code portion: private const int OFN_ENABLESIZING = 0x00800000; private const int OFN_EXPLORER = 0x00080000; private const int OFN_ENABLEHOOK = 0x00000020; protected override bool RunDialog(IntPtr hwndOwner) { OPENFILENAME_I.WndProc proc = new OPENFILENAME_I.WndProc(this.HookProc); OPENFILENAME_I ofn = new OPENFILENAME_I(); this._charBuffer = CharBuffer.CreateBuffer(0x2000); if (this._fileNames != null) { this._charBuffer.PutString(this._fileNames[0]); } ofn.lStructSize = Marshal.SizeOf(typeof(OPENFILENAME_I)); ofn.hwndOwner = hwndOwner; ofn.hInstance = IntPtr.Zero; ofn.lpstrFilter = MakeFilterString(this._filter, this.DereferenceLinks); ofn.nFilterIndex = this._filterIndex; ofn.lpstrFile = this._charBuffer.AllocCoTaskMem(); ofn.nMaxFile = this._charBuffer.Length; ofn.lpstrInitialDir = this._initialDirectory; ofn.lpstrTitle = this._title; ofn.Flags = OFN_EXPLORER | OFN_ENABLESIZING | OFN_ENABLEHOOK; ofn.lpfnHook = proc; ofn.FlagsEx = 0x1000000 ; NativeMethods.GetOpenFileName(ofn); // } [SecurityCritical, SuppressUnmanagedCodeSecurity, DllImport("comdlg32.dll", CharSet = CharSet.Unicode, SetLastError = true)] internal static extern bool GetOpenFileName([In, Out] OPENFILENAME_I ofn);

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  • Same random numbers from instantiated class

    - by user1797202
    I'm learning C# and created a class within my program that holds a random number generator: class RandomNumberGenerator { Random RNG = new Random(); // A bunch of methods that use random numbers are in here } Inside this class are a few methods that use the RNG. Data gets sent here from other parts of the program, gets processed, then gets returned. One of the methods does the following: // Method works something like this int Value1 = RNG.Next(x, y); int Value2 = RNG.Next(x, y); int Value3 = RNG.Next(x, y); The x, y values are to be sent here from another class. So, I have to create an instance of the RandomNumberGenerator within that class so I can call its methods and pass the x and y values to it. class DoStuff { RandomNumberGenerator Randomizer = new RandomNumberGenerator // Here I call a bunch of Randomizer methods that give me values I need } The problem in the above method is that I get the same numbers every time for all three values. I'm not sure if it's because they're so close together and Randomizer's seed value hasn't had time to change or if I'm doing something wrong when I create a new instance of the RandomNumberGenerator class. I've gone through a bunch of answers on here already and typically problems like this are due to people creating many new Random objects when they run methods (thus setting the seed for all of them to the same value), but the only new Random object I create is within the RandomNumberGenerator class. I then instantiate that once within the other class so I can pass it data and use its methods. Why is this happening and how would I fix this?

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  • Assigning a value to an integer in a C linked list

    - by Drunk On Java
    Hello all. I have a question regarding linked lists. I have the following structs and function for example. struct node { int value; struct node *next; }; struct entrynode { struct node *first; struct node *last; int length; }; void addnode(struct entrynode *entry) { struct node *nextnode = (struct node *)malloc(sizeof(struct node)); int temp; if(entry->first == NULL) { printf("Please enter an integer.\n"); scanf("%d", &temp); nextnode->value = temp; nextnode->next = NULL; entry->first = nextnode; entry->last = nextnode; entry->length++; } else { entry->last->next = nextnode; printf("Please enter an integer.\n"); scanf("%d", nextnode->value); nextnode->next = NULL; entry->last = nextnode; entry->length++; } } In the first part of the if statement, I store input into a temp variable and then assign that to a field in the struct. The else branch, I tried to assign it directly which did not work. How would I go about assigning it directly? Thanks for your time.

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  • std::stringstream GCC Abnormal Behavior

    - by FlorianZ
    I have a very interesting problem with compiling a short little program on a Mac (GCC 4.2). The function below would only stream chars or strings into the stringstream, but not anything else (int, double, float, etc.) In fact, the fail flag is set if I attempt to convert for example an int into a string. However, removing the preprocessor flag: _GLIBCXX_DEBUG=1, which is set by default in XCode for the debug mode, will yield the desired results / correct behavior. Here is the simple function I am talking about. value is template variable of type T. Tested for int, double, float (not working), char and strings (working). template < typename T > const std::string Attribute<T>::getValueAsString() const { std::ostringstream stringValue; stringValue << value; return stringValue.str(); } Any ideas what I am doing wrong, why this doesn't work, or what the preprocessor flag does to make this not work anymore? Thanks!

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  • Understanding C++ pointers (when they point to a pointer)

    - by Stephano
    I think I understand references and pointers pretty well. Here is what I (think I) know: int i = 5; //i is a primitive type, the value is 5, i do not know the address. int *ptr; //a pointer to an int. i have no way if knowing the value yet. ptr = &i; //now i have an address for the value of i (called ptr) *ptr = 10; //go get the value stored at ptr and change it to 10 Please feel free to comment or correct these statements. Now I'm trying to make the jump to arrays of pointers. Here is what I do not know: char **char_ptrs = new char *[50]; Node **node_ptrs = new Node *[50]; My understanding is that I have 2 arrays of pointers, one set of pointers to chars and one to nodes. So if I wanted to set the values, I would do something like this: char_ptrs[0] = new char[20]; node_ptrs[0] = new Node; Now I have a pointer, in the 0 position of my array, in each respective array. Again, feel free to comment here if I'm confused. So, what does the ** operator do? Likewise, what is putting a single * next to the instantiation doing (*[50])? (what is that called exactly, instantiation?)

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  • C++: calling member functions within constructor?

    - by powerboy
    The following code raises a runtime error: #include <iostream> #include <iterator> #include <ext/slist> class IntList : public __gnu_cxx::slist<int> { public: typedef IntList::iterator iterator; IntList() { tail_ = begin(); } // seems that there is a problem here void append(const int node) { tail_ = insert_after(tail_, node); } private: iterator tail_; }; int main() { IntList list; list.append(1); list.append(2); list.append(3); for (IntList::iterator i = list.begin(); i != list.end(); ++i) { std::cout << *i << " "; } return 0; } Seems that the problem is in the constructor IntList(). Is it because it calls the member function begin()?

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  • Attempted GCF app for Android

    - by Aaron
    I am new to Android and am trying to create a very basic app that calculates and displays the GCF of two numbers entered by the user. Here is a copy of my GCF.java: package com.example.GCF; import java.util.Arrays; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; public class GCF extends Activity { private TextView mAnswer; private EditText mA, mB; private Button ok; private String A, B; private int iA, iB; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mA = (EditText) findViewById(R.id.entry); mB = (EditText) findViewById(R.id.entry1); ok = (Button) findViewById(R.id.ok); mAnswer = (TextView) findViewById(R.id.answer1); ok.setOnClickListener(new OnClickListener() { public void onClick(View v) { A = mA.getText().toString(); B = mB.getText().toString(); } }); // the String to int conversion happens here iA = Integer.parseInt(A.trim()); iB = Integer.parseInt(B.trim()); while (iA != iB) { int[] nums={ iA, iB, Math.abs(iA-iB) }; Arrays.sort(nums); iA=nums[0]; iB=nums[1]; } updateDisplay(); } private void updateDisplay() { mAnswer.setText( new StringBuilder().append(iA)); } } Any Suggestions? Thank you!

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  • Automatically update php loop with data pulled from database

    - by John Svensson
    SQL STRUCTURE CREATE TABLE IF NOT EXISTS `map` ( `id` int(11) NOT NULL AUTO_INCREMENT, `x` int(11) NOT NULL, `y` int(11) NOT NULL, `type` varchar(50) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ; http://localhost/map.php?x=0&y=0 When I update the x and y via POST or GET, I would like to pull the new data from the database without refreshing the site, how would I manage that? Could someone give me some examples, because I am really stuck here. <?php mysql_connect('localhost', 'root', ''); mysql_select_db('hol'); $startX = $_GET['x']; $startY = $_GET['y']; $fieldHeight = 6; $fieldWidth = 6; $sql = "SELECT id, x, y, type FROM map WHERE x BETWEEN ".$startX." AND ".($startX+$fieldWidth). " AND y BETWEEN ".$startY." AND ".($startY+$fieldHeight); $result = mysql_query($sql); $positions = array(); while ($row = mysql_fetch_assoc($result)) { $positions[$row['x']][$row['y']] = $row; } echo "<table>"; for($y=$startY; $y<$startY+$fieldHeight; $y++) { echo "<tr>"; for($x=$startX; $x<$startX+$fieldWidth; $x++) { echo "<td>"; if(isset($positions[$x][$y])) { echo $positions[$x][$y]['type']; } else { echo "(".$x.",".$y.")"; } echo "</td>"; } echo "</tr>"; } echo "</table>"; ?>

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  • Simulation tree command in C

    - by Ecle
    I have to create the simulation of tree command in C, this is my current code: #include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <dirent.h> #include <string.h> main(int argc, char *argv[]){ int i; if(argc < 2){ printf("\nError. Use: %s directory\n", argv[0]); system("exit"); } for(i=1;i<argc;i++) //if(argv[i][0] != '-') tree(argv[i]); } tree(char *ruta){ DIR *dirp; struct dirent *dp; static nivel = 0; struct stat buf; char fichero[256]; int i; if((dirp = opendir(path)) == NULL){ perror(path); return; } while((dp = readdir(dirp)) != NULL){ printf(fichero, "%s/%s", path, dp->d_name); if((buf.st_mode & S_IFMT) == S_IFDIR){ for(i=0;i<nivel;i++) printf("\t"); printf("%s\n", dp->d_name); ++nivel; tree(fichero); --nivel; } } } Apparently, it works! (due to it compiles correctly) But I don't why. I can't pass the correct arguments to execute this. Thank you so much, people.

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  • c++ specialized overload?

    - by acidzombie24
    -edit- i am trying to close the question. i solved the problem with boost::is_base_and_derived In my class i want to do two things. 1) Copy int, floats and other normal values 2) Copy structs that supply a special copy function (template T copyAs(); } the struct MUST NOT return int's unless i explicitly say ints. I do not want the programmer mistaking the mistake by doing int a = thatClass; -edit- someone mention classes dont return anything, i mean using the operator Type() overload. How do i create my copy operator in such a way i can copy both 1) ints, floats etc and the the struct restricted in the way i mention in 2). i tried doing template <class T2> T operator = (const T2& v); which would cover my ints, floats etc. But how would it differentiate from structs? so i wrote T operator = (const SomeGenericBase& v); The idea was the GenericBase would be unsed instead then i can do v.Whatever. But that backfires bc the functions i want wouldnt exist, unless i use virtual, but virtual templates dont exist. Also i would hate to use virtual I think the solution is to get rid of ints and have it convert to something that can do .as(). So i wrote something up but now i have the same problem, how does that differentiate ints and structs that have the .as() function template?

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  • returning a pointed to an object within a std::vector

    - by memC
    I have a very basic question on returning a reference to an element of a vector . There is a vector vec that stores instances of class Foo. I want to access an element from this vector . ( don't want to use the vector index) . How should I code the method getFoo here? #include<vector> #include<stdio.h> #include<iostream> #include<math.h> using namespace std; class Foo { public: Foo(){}; ~Foo(){}; }; class B { public: vector<Foo> vec; Foo* getFoo(); B(){}; ~B(){}; }; Foo* B::getFoo(){ int i; vec.push_back(Foo()); i = vec.size() - 1; // how to return a pointer to vec[i] ?? return vec.at(i); }; int main(){ B b; b = B(); int i = 0; for (i = 0; i < 5; i ++){ b.getFoo(); } return 0; }

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  • Receiving "expected expression before" Error When Using A Struct

    - by Zach Dziura
    I'm in the process of creating a simple 2D game engine in C with a group of friends at school. I'd like to write this engine in an Object-Oriented way, using structs as classes, function pointers as methods, etc. To emulate standard OOP syntax, I created a create() function which allocates space in memory for the object. I'm in the process of testing it out, and I'm receiving an error. Here is my code for two files that I'm using to test: test.c: #include <stdio.h> int main() { typedef struct { int i; } Class; Class *test = (Class*) create(Class); test->i = 1; printf("The value of \"test\" is: %i\n", test->i); return 0; } utils.c: #include <stdio.h> #include <stdlib.h> #include "utils.h" void* create(const void* class) { void *obj = (void*) malloc(sizeof(class)); if (obj == 0) { printf("Error allocating memory.\n"); return (int*) -1; } else { return obj; } } void destroy(void* object) { free(object); } The utils.h file simply holds prototypes for the create() and destroy() functions. When I execute gcc test.c utils.c -o test, I'm receiving this error message: test.c: In function 'main': test.c:10:32: error: expected expression before 'Class' I know it has something to do with my typedef at the beginning, and how I'm probably not using proper syntax. But I have no idea what that proper syntax is. Can anyone help?

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  • update attribute a element in arraylist on java ?

    - by tiendv
    I have a class Class TextChunks extends Token { ArrayList<Token> arrt = new ArrayList<Token>(); } extent fron class : class Token { String s; int frequency = 1 ;// Tern frequency in TextChunk } Now in token i have arraylist token , i want to update attribute frequency of token in Texchunks when have more than one tokens same . For clearly a give a example : Texchunks :" in particular in domain and range in some " So have 8 token : in,particular,in,domain,and,range,in,some i want update attribute frequency for token : in this example when i get attribute frequency of token "in" must return 3 it mean when i call : get frequency of Texchunks when dislay : in 3 particular 1 in 3 domain 1 and 1 range 1 in 3 some 1 here my code : public TextChunks updateFrequencyOfTokenInTextChunks (TextChunks tc) throws CloneNotSupportedException { TextChunks result = (TextChunks) tc.clone(); for (int i =0 ; i< result.arrt.size() ; i++ ){ int j=i+1; if (result.arrt.get(i).compareTwoToken(result.arrt.get(j))== true ) { // help here how to update attribute result.arrt.get(i) // and result.arrt.get(J) = ++ and } } return tc; } Thanks in advandce

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