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  • C++ Filling an 1D array to represent a n-dimensional object based on a straight line segment

    - by Ben
    I'm struggling to find a good way to put this question but here goes. I'm making a system that uses a 1D array implemented as double * parts_ = new double[some_variable];. I want to use this to hold co-ordinates for a particle system that can run in various dimensions. What I want to be able to do is write a generic fill algorithm for filling this in n-dimensions with a common increment in all direction to a variable size. Examples will serve best I think. Consider the case where the number of particles stored by the array is 4 In 1D this produces 4 elements in the array because each particle only has one co-ordinate. 1D: {0, 25, 50, 75}; In 2D this produces 8 elements in the array because each particle has two co-ordinates.. 2D: {0, 0, 0, 25, 25, 0, 25, 25} In 3D this produces 12 elements in the array because each particle now has three co-ordinates {0, 0, 0, 0, 0, 25, 0, 0, 50, ... } These examples are still not quite accurate, but they hopefully will suffice. The way I would do this normally for two dimensions: int i = 0; for(int x = 0; x < parts_size_ / dims_ / dims_ * 25; x += 25) { for(int y = 0; y < parts_size_ / dims_ / dims_ * 25; y += 25) { parts_[i] = x; parts_[i+1] = y; i+=2; // Indentation hates me today .< How can I implement this for n-dimensions where 25 can be any number? The straight line part is because it seems to me logical that a line is a somewhat regular shape in 1D, as is a square in 2D, and a cube in 3D. It seems to me that it would follow that there would be similar shapes in this family that could be implemented for 4D and higher dimensions via a similar fill pattern. This is the shape I wish to set my array to represent.

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  • Declaring a data type dynamically in C++

    - by Bobby
    I want to be able to do the following: I have an array of strings that contain data types: string DataTypeValues[20] = {"char", "unsigned char", "short", "int"}; Then later, I would like to create a variable of one of the data types at runtime. I won't know at compile time what the correct data type should be. So for example, if at runtime I determined a variable x needed to be of type int: DataTypeValues[3] x = 100; Obviously this won't work, so how could I do something like this?

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  • PHP and MySQL SELECT problem.

    - by R.I.P.coalMINERS
    Trying to check if a name is already stored in the database from the login user. The name is a set of dynamic arrays entered by the user threw a set of dynamic form fields added by the user. Can some show me how to check and see if the name is already entered by the login user? I know my code can't be right. Thanks! MySQL code. SELECT * FROM names WHERE name = '" . $_POST['name'] . "' AND userID = '$userID' Here is the MySQL table. 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) );

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  • [C] Read line from file without knowing the line length.

    - by ryyst
    Hi, I want to read in a file line by line, without knowing the line length before. Here's what I got so far: int ch = getc(file); int length = 0; char buffer[4095]; while (ch != '\n' && ch != EOF) { ch = getc(file); buffer[length] = ch; length++; } printf("Line length: %d characters.", length); I can now figure out the line length, but only for lines that are shorter than 4095 characters. Is there a better way to do this (I already used fgets() but got told it wasn't the best way)? --Ry

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  • Possible to convert list of #defines into strings (C++)

    - by brandonC
    Suppose I have a list of #defines in a header file for an external library. These #defines represent error codes returned from functions. I want to write a conversion function that can take as an input an error code and return as an output a string literal representing the actual #define name. As an example, if I have #define NO_ERROR 0 #define ONE_KIND_OF_ERROR 1 #define ANOTHER_KIND_OF_ERROR 2 I would like a function to be able to called like int errorCode = doSomeLibraryFunction(); if (errorCode) writeToLog(convertToString(errorCode)); And have convertToString() be able to auto-convert that error code without being a giant switch-case looking like const char* convertToString(int errorCode) { switch (errorCode) { case NO_ERROR: return "NO_ERROR"; case ONE_KIND_OF_ERROR: return "ONE_KIND_OF_ERROR"; ... ... ... I have a feeling that if this is possible, it would be possible using templates and metaprogramming, but that would only work the error codes were actually a type and not a bunch of processor macros. Thanks

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  • android google maps my location

    - by windblow
    I have google maps activity where i would like to get my location but im facing NullPointerException... locManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); locManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, this); Location location = locManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER); System.out.println("loaded4"); myPoint = new GeoPoint((int)(location.getLatitude()*1E6),(int)(location.getLongitude()*1E6)); System.out.println("loaded5"); I am able to get "loaded4" but not "loaded5" So NullPointer cause is between them. I also tried to use GPS_PROVIDER but it didnt work out. Yes i have all permissions in manifest. Map is able to load in if im not searhing for my loacation. Is it possible its NullPointer because before that i load some other coordinates in same class ? Maybe its emulator fault ? I can give extended code if needed. Using source from http://www.chupamobile.com/tutorial/details/53

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  • C# - Erase all property values from a class?

    - by John M
    In a C# Winforms (3.5) application I have added a class that contains many properties (get/set) used to stored values from a 12 form long process. After form 12 I would like wipe out all the property values in the storing class so that the next user won't accidentally record values when starting the process at form 1. Is it possible to erase/destroy/dispose of all property values in a class? My class looks like this: private static int battery; public int Battery { get { return storeInspectionValues.battery; } set { storeInspectionValues.battery = value; } }

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  • why isn't the input text file being read into the ArrayList<String>, diary?

    - by hmg
    Here's my code: public void readFile() throws IOException { System.out.println("Input file name: "); Scanner in = new Scanner(System.in); String readName = in.nextLine(); Scanner reader = new Scanner(new File(readName)); System.out.println("Reading file..."); while (reader.hasNextLine()) { System.out.println(reader.nextLine()); } System.out.println("File read."); Scanner inAgain = new Scanner(System.in); System.out.println("Would you like to read this into the current Diary?"); System.out.println("Warning: This will overwrite your current Diary!"); String readFileConfirm = inAgain.nextLine(); ArrayList<String> readData = new ArrayList<String>(); if (readFileConfirm.equalsIgnoreCase("yes")) { for (int i = 0; i < readData.size(); i++) { readData.add(reader.nextLine()); } System.out.println("Data added to extra array..."); System.out.println("Here are the contents."); for (int i = 0; i < readData.size(); i++) { System.out.println(readData.get(i)); } System.out.println("Contents read."); System.out.println("Now overwriting current Diary with read file..."); diary.clear(); for (int i = 0; i < diary.size(); i++) { diary.add(readData.get(i)); } System.out.println("New Diary created!"); System.out.println("Use 'recall' to see your new Diary!"); } else { System.out.println("Very well, returning to first command entry."); } } Thanks in advance! -h

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  • Method sscanf() ambiguous behavior

    - by Carmen Cojocaru
    I am trying to understand how sscanf() works. I ran some examples from this page: http://docs.roxen.com/pike/7.0/tutorial/strings/sscanf.xml and they don't work on my platform. I can't understand why. For instance: "sscanf("4711bar", "%d%s", a, b);" makes the program exit with an error... Here is one of the examples that work: "sscanf("foo", "f%s", a);". Does anybody know why? Do they work on your platforms? Thank you. This is my code: int main(void){ char *b = (char*)malloc(sizeof(char)*100); int a = 0; sscanf("4711bar", "%d%s", a, b); printf("%d", a); printf("%s", b); }

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  • django-avatar: cant save thumbnail

    - by Znack
    I'm use django-avatar app and can't make it to save thumbnails. The original image save normally in my media dir. Using the step execution showed that error occurred here image.save(thumb, settings.AVATAR_THUMB_FORMAT, quality=quality) I found this line in create_thumbnail: def create_thumbnail(self, size, quality=None): # invalidate the cache of the thumbnail with the given size first invalidate_cache(self.user, size) try: orig = self.avatar.storage.open(self.avatar.name, 'rb') image = Image.open(orig) quality = quality or settings.AVATAR_THUMB_QUALITY w, h = image.size if w != size or h != size: if w > h: diff = int((w - h) / 2) image = image.crop((diff, 0, w - diff, h)) else: diff = int((h - w) / 2) image = image.crop((0, diff, w, h - diff)) if image.mode != "RGB": image = image.convert("RGB") image = image.resize((size, size), settings.AVATAR_RESIZE_METHOD) thumb = six.BytesIO() image.save(thumb, settings.AVATAR_THUMB_FORMAT, quality=quality) thumb_file = ContentFile(thumb.getvalue()) else: thumb_file = File(orig) thumb = self.avatar.storage.save(self.avatar_name(size), thumb_file) except IOError: return # What should we do here? Render a "sorry, didn't work" img? maybe all I need is just some library? Thanks

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  • Understanding c++ block of code

    - by kotoko
    I was given a c++ main and have to code it so it works. I am having some trouble understanding the code as I am a bit new to cpp. Here is the code int main(int argc, char *argv[]) { Class::setAtribute("string"); Class(Class::CONSTANT) << "starting up..."; } Some questions: How can the first line work with no variables? Is it static? The second line is really strange for me, what I can make out is a Constructor that takes in a class constante and then prints it out somehow? If someone could explain me this bit of code it would be great! Thanks in advance.

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  • quick sort problem

    - by farka
    I use qsort from C libary and I have datatype Element_type **pElement and Element_type is struct typedef element_type {int ,char ....} example, and i call quicksor function with qsort(*pElement,iCountElement,(size_t)sizeof(Element_type),compare); and callback function static int compare(const void *p1, const void *p2) { Element_type *a1 = (Element_type *)p1; Element_type *a2 = (Element_type *)p2; return ( (a2)->iServiceId < (a1)->iServiceId ); } but I always get segmentation fault. Why?

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  • Why does C++ allow variable length arrays that aren't dynamically allocated?

    - by Maulrus
    I'm relatively new to C++, and from the beginning it's been drilled into me that you can't do something like int x; cin >> x; int array[x]; Instead, you must use dynamic memory. However, I recently discovered that the above will compile (though I get a -pedantic warning saying it's forbidden by ISO C++). I know that it's obviously a bad idea to do it if it's not allowed by the standard, but I previously didn't even know this was possible. My question is, why does g++ allow variable length arrays that aren't dynamically allocated if it's not allowed by the standard? Also, if it's possible for the compiler to do it, why isn't it in the standard?

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  • C++ Array of Variable sized Arrays

    - by adam
    I am very new to C++ and I realise the following is not necessarily as easy as I'd like it to be, but I'd really appreciate a more expert opinion. I am essentially trying to achieve a dynamic iteration over a variable sized array of variable sized arrays similar to the following. String *2d_array[][] = {{"A1","A2"},{"B1","B2","B3"},{"C1"}}; for (int i=0; i<2d_array.length; i++) { for (int j=0; j<2d_array[i].length; j++) { print(2d_array[i][j]); } } Is there a reasonable way to do this? Perhaps by using a vector, or another struct? Thanks :)

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  • Is it a good or bad practice to call instance methods from a java constructor?

    - by Steve
    There are several different ways I can initialize complex objects (with injected dependencies and required set-up of injected members), are all seem reasonable, but have various advantages and disadvantages. I'll give a concrete example: final class MyClass { private final Dependency dependency; @Inject public MyClass(Dependency dependency) { this.dependency = dependency; dependency.addHandler(new Handler() { @Override void handle(int foo) { MyClass.this.doSomething(foo); } }); doSomething(0); } private void doSomething(int foo) { dependency.doSomethingElse(foo+1); } } As you can see, the constructor does 3 things, including calling an instance method. I've been told that calling instance methods from a constructor is unsafe because it circumvents the compiler's checks for uninitialized members. I.e. I could have called doSomething(0) before setting this.dependency, which would have compiled but not worked. What is the best way to refactor this? Make doSomething static and pass in the dependency explicitly? In my actual case I have three instance methods and three member fields that all depend on one another, so this seems like a lot of extra boilerplate to make all three of these static. Move the addHandler and doSomething into an @Inject public void init() method. While use with Guice will be transparent, it requires any manual construction to be sure to call init() or else the object won't be fully-functional if someone forgets. Also, this exposes more of the API, both of which seem like bad ideas. Wrap a nested class to keep the dependency to make sure it behaves properly without exposing additional API:class DependencyManager { private final Dependency dependency; public DependecyManager(Dependency dependency) { ... } public doSomething(int foo) { ... } } @Inject public MyClass(Dependency dependency) { DependencyManager manager = new DependencyManager(dependency); manager.doSomething(0); } This pulls instance methods out of all constructors, but generates an extra layer of classes, and when I already had inner and anonymous classes (e.g. that handler) it can become confusing - when I tried this I was told to move the DependencyManager to a separate file, which is also distasteful because it's now multiple files to do a single thing. So what is the preferred way to deal with this sort of situation?

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  • What is the most efficient method to find x contiguous values of y in an array?

    - by Alec
    Running my app through callgrind revealed that this line dwarfed everything else by a factor of about 10,000. I'm probably going to redesign around it, but it got me wondering; Is there a better way to do it? Here's what I'm doing at the moment: int i = 1; while ( ( (*(buffer++) == 0xffffffff && ++i) || (i = 1) ) && i < desiredLength + 1 && buffer < bufferEnd ); It's looking for the offset of the first chunk of desiredLength 0xffffffff values in a 32 bit unsigned int array. It's significantly faster than any implementations I could come up with involving an inner loop. But it's still too damn slow.

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  • C struct print, decode this code?

    - by pauliwago
    I am in the process of studying for a test, and I'm trying to work through some practice problems. I've been working on this a while now..but can't figure it out. Please take a look at the code fragment: union { int i; short x; unsigned short u; float f; } testout; testout.i=0xC0208000; Before I ask the question, can someone please explain to me how the above code works?? My guess is that testout.i=0xC0208000 puts either an int, short, unsigned short, or float and puts the result in that address. (?) The question is what prints out if we write printf("%d", testout.x)? I know we should expect digits....but I have no idea where they are getting the digits from....there is no output. Any explanation would be greatly appreciated. Thanks!

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  • Correct way to clear/release an array of arrays

    - by iFloh
    And again my array of arrays .... When I have an array "x" that contains multiple instances of an array "y", how do I clear/release it without risking memory leaks? are the following calls sufficient? (a) clearing the array [x removeAllObjects]; (b) releasing the array [x release]; or do I need to enumerate the array, such as: (c) clearing the array for(int i=0;i<x.count;i++) [[x objectAtIndex:i] release]; [x removeAllObjects]; (d) releasing the array for(int i=0;i<x.count;i++) [[x objectAtIndex:i] release]; [x release]; thanks in advance

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  • Is it guaranteed that new Integer(i) == i in Java?

    - by polygenelubricants
    Consider the following snippet: int i = 99999999; byte b = 99; short s = 9999; Integer ii = Integer.valueOf(9); // should be within cache System.out.println(new Integer(i) == i); // "true" System.out.println(new Integer(b) == b); // "true" System.out.println(new Integer(s) == s); // "true" System.out.println(new Integer(ii) == ii); // "false" It's obvious why the last line will ALWAYS prints "false": we're using == reference identity comparison, and a new object will NEVER be == to an already existing object. The question is about the first 3 lines: are those comparisons guaranteed to be on the primitive int, with the Integer auto-unboxed? Are there cases where the primitive would be auto-boxed instead, and reference identity comparisons are performed? (which would all then be false!)

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  • Simple, Custom Parsing with c++

    - by bradkovach
    Hi! I have been reading SO for some time now, but I truly cannot find any help for my problem. I have a c++ assignment to create an IAS simulator. Here is some sample code... 0 1 a 1 2 b 2 c 3 1 10 begin 11 . load a, subtract b and offset by -1 for jump+ 11 load M(0) 12 sub M(1) 13 sub M(3) 14 halt Using c++, I need to be able to read these lines and store them in a "memory register" class that I already have constructed... For example, the first line would need to store "1 a" in register zero. How can I parse out the number at the line beginning and then store the rest as a string? I have setup storage using a class that is called using mem.set(int, string);. int is the memory location at the beginning of the line and string is the stored instruction.

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  • Contacts activity doesn't return data

    - by Mike
    In my app I simply open the list of activities and when a contact is clicked I attempt to retrieve the name of the contact selected and put it into a string. The app crashes in the onActivityResult() function. I do have the READ_CONTACTS permission set. /** * Opens the contacts activity */ public void openContacts() { Intent intent = new Intent(Intent.ACTION_PICK, People.CONTENT_URI); startActivityForResult(intent, PICK_CONTACT); } @Override public void onActivityResult(int reqCode, int resultCode, Intent data) { super.onActivityResult(reqCode, resultCode, data); switch (reqCode) { case (PICK_CONTACT) : if (resultCode == Activity.RESULT_OK) { Uri contactData = data.getData(); Cursor c = managedQuery(contactData, null, null, null, null); //NullPointerException thrown here, line 102 if (c.moveToFirst()) { String name = c.getString(c.getColumnIndexOrThrow(People.NAME)); FRIEND_NAME = name; showConfirmDialog(name); } } break; } } The following logcat error logs are returned: Any help is appreciated. Thanks

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  • new operator overwriting an existing object

    - by dvpdiner2
    I have a custom FastStack class, implemented as a fixed size array and an index into that array. In my copy constructor, I allocate the array and then assign each object from the copy's array into the new array. There's some refcounting in the objects on the stack, hence assignment is used rather than a simple copy. The problem is that when allocating the array, it sometimes overwrites part of the other stack's array. As can be expected, this leads to eventual segmentation faults when that data is dereferenced. class FastStack { private: int m_size, m_ptr; ObjectRef* m_stack; public: FastStack(int size) : m_size(size), m_ptr(-1) { m_stack = new ObjectRef[m_size]; } FastStack(const FastStack& copy) : m_size(copy.m_size), m_ptr(copy.m_ptr) { long a = (long)copy.m_stack[0]; m_stack = new ObjectRef[m_size]; if ((long)copy.m_stack[0] != a) fprintf(stderr, "\nWe have a serious problem!\n\n"); for (int i = 0; i <= m_ptr; i++) m_stack[i] = copy.m_stack[i]; } ~FastStack() { delete[] m_stack; } }; class ObjectRef { private: DataObj* m_obj; public: ObjectRef() : m_obj(0) { } ObjectRef(DataObj* obj) : m_obj(obj) { if (m_obj) m_obj->addRef(); } ObjectRef(const ObjectRef& obj) : m_obj(obj.m_obj) { if (m_obj) m_obj->addRef(); } ~ObjectRef() { if (m_obj) m_obj->delRef(); } ObjectRef& operator=(DataObj* obj) { if (obj) obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj; return *this; } ObjectRef& operator=(const ObjectRef& obj) { if (obj.m_obj) obj.m_obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj.m_obj; return *this; } }; I see that "We have a serious problem!" line shortly before a segfault, and stepping through it with gdb I can see that one of the ObjectRefs created by new has the same address as the other stack's array. My first instinct is to say that new should never be allocating memory that is already in use, but that clearly seems to be the case here and I am at a complete loss as to what can be done. Added: At the time that I see this happen, m_size = 2 and m_ptr = 0.

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  • MySQL Query, Date Range From "Blacklist"

    - by erbaker
    I have 2 databases. One is properties and the other is dates. In dates I have associated the land_id and a date (In YYYYMMDD format) which means that the date is not available. I need to formulate a query that a user can specify a start and end date, and then choose a property for which dates are available (not in the date database). How do airline and hotel websites do this kind of logic? I was thinking about taking the date range and picking all days in between and doing a query where the dates do not match and ordering it by number of results, but I can see how that could easily turn into an intense query. CREATE TABLE IF NOT EXISTS `dates` ( `id` int(11) NOT NULL AUTO_INCREMENT, `land_id` int(11) NOT NULL, `date` varchar(255) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=44 ; -- -- Dumping data for table `dates` -- INSERT INTO `dates` (`id`, `land_id`, `date`) VALUES (43, 1, '20100526'), (39, 1, '20100522'), (40, 1, '20100523'), (41, 1, '20100521'), (42, 1, '20100525');

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  • There is more then one Point class

    - by Dmitry
    Today I hit something very annoying while working with one of my colleagues. It seems there are two Point classes in .NET and by mistake we were trying for a good few minutes to figure out why our "Point(x,y)" wouldn’t take double, but only Int. Turns out we were using the wrong one since the XAML element in question needed the version with Double. So, based on what you actually want to do, make sure you’re using the right namespace. Please see below for MSDN reference links for each namespace version of Point, hope this saves you some time. System.Windows Point (MSDN Ref - Double version) System.Dawing Point (MSDN Ref - Int version)

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