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  • CakePHP - Sorting using HABTM Join Table Field

    - by Ashok
    Hello Cake Gurus, here's my problem: Table1: Posts id - int title - varchar Table2: Categories id - int name - varchar HABTM JoinTable: categories_posts id - int post_id - int category_id - int postorder - int As you can see, the join table contains a field called 'postorder' - This is for ordering the posts in a particular category. For example, Posts: Post1, Post2, Post3, Post4 Categories: Cat1, Cat2 Ordering: Cat1 - Post1, Post3, Post2 Cat2 - Post3, Post1, Post4 Now in CakePHP, $postpages = $this->Post->Category->find('all'); gives me a array like Array ( [0] => Array ( [Category] => Array ( [id] => 13 [name] => Cat1 ) [Post] => Array ( [0] => Array ( [id] => 1 [title] => Post2 [CategoriesPost] => Array ( [id] => 17 [post_id] => 1 [category_id] => 13 [postorder] => 3 ) ) [1] => Array ( [id] => 4 [title] => Post1 [CategoriesPost] => Array ( [id] => 21 [post_id] => 4 [category_id] => 13 [postorder] => 1 ) ) ) ) ) As you can see [Post], they are not ordered according to [CategoriesPost].postorder but are ordered according to [CategoriesPost].id. How can I get the array ordered according to [CategoriesPost].postorder? Thanks in advance for your time :) Edit: The Queries from Cake's SQL Log are: SELECT `Category`.`id`, `Category`.`name` FROM `categories` AS `Category` WHERE 1 = 1 SELECT `Post`.`id`, `Post`.`title`, `CategoriesPost`.`id`, `CategoriesPost`.`post_id`, `CategoriesPost`.`category_id`, `CategoriesPost`.`postorder` FROM `posts` AS `Post` JOIN `categories_posts` AS `CategoriesPost` ON (`CategoriesPost`.`category_id` IN (13, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52) AND `CategoriesPost`.`post_id` = `Post`.`id`) What I am looking for is how to make cake put a Order By CategoriesPost.postorder in that second SELECT SQL Query.

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  • Why I'm not getting "Multiple definition" error from the g++?

    - by ban
    I tried to link my executable program with 2 static libraries using g++. The 2 static libraries have the same function name. I'm expecting a "multiple definition" linking error from the linker, but I did not received. Can anyone help to explain why is this so? staticLibA.h #ifndef _STATIC_LIBA_HEADER #define _STATIC_LIBA_HEADER int hello(void); #endif staticLibA.cpp #include "staticLibA.h" int hello(void) { printf("\nI'm in staticLibA\n"); return 0; } output: g++ -c -Wall -fPIC -m32 -o staticLibA.o staticLibA.cpp ar -cvq ../libstaticLibA.a staticLibA.o a - staticLibA.o staticLibB.h #ifndef _STATIC_LIBB_HEADER #define _STATIC_LIBB_HEADER int hello(void); #endif staticLibB.cpp #include "staticLibB.h" int hello(void) { printf("\nI'm in staticLibB\n"); return 0; } output: g++ -c -Wall -fPIC -m32 -o staticLibB.o staticLibB.cpp ar -cvq ../libstaticLibB.a staticLibB.o a - staticLibB.o main.cpp extern int hello(void); int main(void) { hello(); return 0; } output: g++ -c -o main.o main.cpp g++ -o multipleLibsTest main.o -L. -lstaticLibA -lstaticLibB -lstaticLibC -ldl -lpthread -lrt

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  • Extracting exported functions out of a shared lib (ubuntu)

    - by Pingu
    the title already describes my problem. I found this post, but it didn't completely answers my question. With the help of it i got this output from nm... $nm -C -g -D ./libLoggingHandler.so 000000cc A _DYNAMIC ... 000042e0 T write_str(char*, char const*, int*) 00005a78 T RingBuffer::WriteUnlock() ... 00005918 T TraceLines::GetItemSize() ... U SharedMemory::attach(int, void const*, int) ... 00003810 T TraceProfile::FindLineNr(int, int) ... 00002d40 T LoggingHandler::getLogLevel() ... U SharedResource::getSharedResourceKey(char const*, int) ... which are the exported functions? I already found a hint in this post, that the "T" indicates that its getting exported. But if i check the nm manual here, it just says T - The symbol is in the text (code) section. My questions is: Does this output give me the information which functions are exported functions (or variables)? If not, how do i get it? Greetings, Pingu

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  • AudioRecord - empty buffer

    - by Arxas
    I' m trying to record some audio using AudioRecord class. Here is my code: int audioSource = AudioSource.MIC; int sampleRateInHz = 44100; int channelConfig = AudioFormat.CHANNEL_IN_MONO; int audioFormat = AudioFormat.ENCODING_PCM_16BIT; int bufferSizeInShorts = 44100; int bufferSizeInBytes = 2*bufferSizeInShorts; short Data[] = new short[bufferSizeInShorts]; Thread recordingThread; AudioRecord audioRecorder = new AudioRecord(audioSource, sampleRateInHz, channelConfig, audioFormat, bufferSizeInBytes); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.activity_main, menu); return true; } public void startRecording(View arg0) { audioRecorder.startRecording(); recordingThread = new Thread(new Runnable() { public void run() { while (Data[bufferSizeInShorts-1] == 0) audioRecorder.read(Data, 0, bufferSizeInShorts); } }); audioRecorder.stop(); } Unfortunately my short array is empty after the recording is over. May I kindly ask you to help me figure out what's wrong?

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  • get and set for class in model - MVC 2 asp.net

    - by bergin
    Hi there, I want to improve the program so it has a proper constructor but also works with the models environment of MVC. I currently have: public void recordDocument(int order_id, string filename, string physical_path, string slug, int bytes) { ArchiveDocument doc = new ArchiveDocument(); doc.order_id = order_id; doc.filename = filename; doc.physical_path = physical_path; doc.slug = slug; doc.bytes = bytes; db.ArchiveDocuments.InsertOnSubmit(doc); } This obviously should be a constructor and should change to the leaner: public void recordDocument(ArchiveDocument doc) { db.ArchiveDocuments.InsertOnSubmit(doc); } with a get & set somewhere else - not sure of the syntax - do I create a partial class? so: creating in the somewhere repository - ArchiveDocument doc = new ArchiveDocument(order_id, idTaggedFilename, physical_path, slug, bytes); and then: namespace ordering.Models { public partial class ArchiveDocument { int order_id, string filename, string physical_path, string slug, int bytes; public archiveDocument(int order_id, string filename, string physical_path, string slug, int bytes){ this.order_id = order_id; etc } } How should I alter the code?

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  • give feedback on this pointer program

    - by JohnWong
    This is relatively simple program. But I want to get some feedback about how I can improve this program (if any), for example, unnecessary statements? #include<iostream> #include<fstream> using namespace std; double Average(double*,int); int main() { ifstream inFile("data2.txt"); const int SIZE = 4; double *array = new double(SIZE); double *temp; temp = array; for (int i = 0; i < SIZE; i++) { inFile >> *array++; } cout << "Average is: " << Average(temp, SIZE) << endl; } double Average(double *pointer, int x) { double sum = 0; for (int i = 0; i < x; i++) { sum += *pointer++; } return (sum/x); } The codes are valid and the program is working fine. But I just want to hear what you guys think, since most of you have more experience than I do (well I am only a freshman ... lol) Thanks.

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  • iterators to range of elements in a vector whose attributes have specific value

    - by user1801173
    I have a vector of objects and I want to return the range of elements whose attribute have a specific value. This is the structure: class A { public: std::vector<B*> vec_; pair<vector<B*>::iterator, vector<B*>::iterator> getElements(unsigned int attr_val); unsigned int name() { return name_; } private: unsigned int name_; }; class B { public: unsigned int attr() { return attr_; } A* source() { return source_; } B* dest() { return dest_; } private: A* source_; B* dest_; unsigned int attr_; }; The vector vec_; is already sorted by attr_ and dest_-name() (in that order). Now I want to return all elements, whose attr_ is equal to attr_val. What is the appropriate stl algorithm (or is there even a vector member function?) to implement getElements(unsigned int attr_val) ? Thanks for help.

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  • Why does DeviceIoControl throw error 21 (Device Not Ready) from C# when the equivalent in C works fine?

    - by Ragesh
    I'm trying to send an IOCTL_SERVICE_REFRESH command to the GPS Intermediate Driver service using C# like this: handle = CreateFile("GPD0:", GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, IntPtr.Zero, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, IntPtr.Zero); if (handle.ToInt32() == INVALID_HANDLE_VALUE) { rc = Marshal.GetLastWin32Error(); return rc; } int numBytesReturned = 0; rc = DeviceIoControl( handle, IOCTL_SERVICE_REFRESH, null, 0, null, 0, ref numBytesReturned, IntPtr.Zero); int error = Marshal.GetLastWin32Error(); GetLastWin32Error always gives me error 21 (device not ready). However, the equivalent call when made from C++ works fine: HANDLE hGPS = CreateFile(L"GPD0:", GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0); if (hGPS != INVALID_HANDLE_VALUE) { BOOL ret = DeviceIoControl(hGPS,IOCTL_SERVICE_REFRESH,0,0,0,0,0,0); DWORD err = GetLastError(); } I suspected a problem with the PInvoke signatures, but I can't seem to find anything wrong here: [DllImport("coredll.dll", EntryPoint = "DeviceIoControl", SetLastError = true)] public static extern int DeviceIoControl( IntPtr hDevice, uint dwIoControlCode, byte[] lpInBuffer, int nInBufferSize, byte[] lpOutBuffer, int nOutBufferSize, ref int lpBytesReturned, IntPtr lpOverlapped); [DllImport("coredll.dll", SetLastError = true)] public static extern IntPtr CreateFile( String lpFileName, uint dwDesiredAccess, uint dwShareMode, IntPtr attr, uint dwCreationDisposition, uint dwFlagsAndAttributes, IntPtr hTemplateFile); What am I missing here?

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  • How to get from JRuby a correctly typed ruby implementation of a Java interface?

    - by Guss
    I'm trying to use JRuby (through the JSR233 interface included in JRuby 1.5) from a Java application to load a ruby implementation of a Java interface. My sample implementation looks like this: Interface: package some.package; import java.util.List; public interface ScriptDemoIf { int fibonacci(int d); List<String> filterLength(List<String> source, int maxlen); } Ruby Implementation: require 'java' include Java class ScriptDemo java_implements some.package.ScriptDemoIf java_signature 'int fibonacci(int d)' def fibonacci(d) d < 2 ? d : fibonacci(d-1) + fibonacci(d-2) end java_signature 'List<String> filterLength(List<String> source, int maxlen)' def filterLength(source, maxlen) source.find_all { |str| str.length <= maxlen } end end Class loader: public ScriptDemoIf load(String filename) throws ScriptException { ScriptEngine engine = new ScriptEngineManager().getEngineByName("jruby"); FileReader script = new FileReader(filename); try { engine.eval(new FileReader(script)); } catch (FileNotFoundException e) { throw new ScriptException("Failed to load " + filename); } return (ScriptDemoIf) m_engine.eval("ScriptDemo.new"); } (Obviously the loader is a bit more generic in real life - it doesn't assume that the implementation class name is "ScriptDemo" - this is just for simplicity). Problem - I get a class cast exception in the last line of the loader - the engine.eval() return a RubyObject type which doesn't cast down nicely to my interface. From stuff I read all over the web I was under the impression that the whole point of use java_implements in the Ruby section was for the interface implementations to be compiled in properly. What am I doing wrong?

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  • Uniform grid Rows and Columns

    - by Carlo
    I'm trying to make a grid based on a UniformGrid to show the coordinates of each cell, and I want to show the values on the X and Y axes like so: _A_ _B_ _C_ _D_ 1 |___|___|___|___| 2 |___|___|___|___| 3 |___|___|___|___| 4 |___|___|___|___| Anyway, in order to do that I need to know the number of columns and rows in the Uniform grid, and I tried overriding the 3 most basic methods where the arrangement / drawing happens, but the columns and rows in there are 0, even though I have some controls in my grid. What method can I override so my Cartesian grid knows how many columns and rows it has? C#: public class CartesianGrid : UniformGrid { protected override Size MeasureOverride(Size constraint) { Size size = base.MeasureOverride(constraint); int computedColumns = this.Columns; // always 0 int computedRows = this.Rows; // always 0 return size; } protected override Size ArrangeOverride(Size arrangeSize) { Size size = base.ArrangeOverride(arrangeSize); int computedColumns = this.Columns; // always 0 int computedRows = this.Rows; // always 0 return size; } protected override void OnRender(DrawingContext dc) { int computedColumns = this.Columns; // always 0 int computedRows = this.Rows; // always 0 base.OnRender(dc); } } XAML: <local:CartesianGrid> <Label Content="Hello" /> <Label Content="Hello" /> <Label Content="Hello" /> <Label Content="Hello" /> <Label Content="Hello" /> <Label Content="Hello" /> </local:CartesianGrid> Any help is greatly appreciated. Thanks!

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  • search a listview in Persian

    - by user3641353
    I have listview with textview which I use textview for search items in listview. It works true but just in English. I can not change the keyboard to Persian. Do you have any solution? this is my code: ArrayAdapter<String> adapter; String[] allMovesStr = {"??? ???? ????","?? ???? ????","?? ???? ????? ???????"}; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.all_moves); adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, allMovesStr); setListAdapter(adapter); EditText ed = (EditText) findViewById(R.id.inputSearch); ListView lv = (ListView) findViewById(android.R.id.list); lv.setTextFilterEnabled(true); ed.addTextChangedListener(new TextWatcher() { public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) { // TODO Auto-generated method stub } public void beforeTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) { // TODO Auto-generated method stub } public void afterTextChanged(Editable arg0) { // vaghti kar bar harfi vared kard josteju mikone : AllMoves.this.adapter.getFilter().filter(arg0); } }); }

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  • C# Finding 2 positions 1-dimArray

    - by Chris
    Hello, In a method i am calculating the longest row of elements. The 1-dim array is filled up with random values (0 or 1). The method looks up the longest row (being 0 or 1, whatever is the longest). Meaning in for example: 1110100 --> the longest row would be 3 (3 * 1) 0110000 --> the longest row would be 4 (4 * 0) My problem is i am trying to perform some type of linear search to show the position of the row in the array. The first example has the longest row of 3 elements (3 times 1). For 1110100 the position in the array would be 0 - 2 (index) For 0110000 the position in the array would be 3 - 6 (index) I have been trying with foreaches, for loops etc..but i cannot seem to get the proper indexes of both. Cannot seem to display both positions properly. For the first example the correct output wouldbe: The largest row of same elements of the array consists of 3 elements on the position 0 - 2. The longest row of elements gets of same elements get calculated as the following: public int BerekenDeelrij (int [] table) ( int count = 0; final int value = 0; int largest = 0; foreach (int value in table) ( if (value == last value) counter + +; else ( largest = Math.Max largest (largest, counter); final value = value count = 1; ) ) Math.Max return (largest, counter); ) Best Regards.

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  • What's the most trivial function that would benfit from being computed on a GPU?

    - by hanDerPeder
    Hi. I'm just starting out learning OpenCL. I'm trying to get a feel for what performance gains to expect when moving functions/algorithms to the GPU. The most basic kernel given in most tutorials is a kernel that takes two arrays of numbers and sums the value at the corresponding indexes and adds them to a third array, like so: __kernel void add(__global float *a, __global float *b, __global float *answer) { int gid = get_global_id(0); answer[gid] = a[gid] + b[gid]; } __kernel void sub(__global float* n, __global float* answer) { int gid = get_global_id(0); answer[gid] = n[gid] - 2; } __kernel void ranksort(__global const float *a, __global float *answer) { int gid = get_global_id(0); int gSize = get_global_size(0); int x = 0; for(int i = 0; i < gSize; i++){ if(a[gid] > a[i]) x++; } answer[x] = a[gid]; } I am assuming that you could never justify computing this on the GPU, the memory transfer would out weight the time it would take computing this on the CPU by magnitudes (I might be wrong about this, hence this question). What I am wondering is what would be the most trivial example where you would expect significant speedup when using a OpenCL kernel instead of the CPU?

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  • ExpandableListView.setAdapter() throws IllegalStateException

    - by vijay
    I am getting the following exception: java.lang.IllegalStateException: get field slot from row 0 col -1 failed when I call setAdapter() on my ExpandableListView. Can someone please help me fix this problem? (I have already wasted 2 days :( ) Cursor mCursor = tasksListCursor(); Log.i("ChronicleTaskList", "rowcount: "+mCursor.getCount()); startManagingCursor(mCursor); boolean flag = mCursor.moveToFirst(); while (flag) { // This loop executes fine. long id = mCursor.getLong(mCursor.getColumnIndexOrThrow(ChronicleDb.KEY_ID)); String name = mCursor.getString(mCursor.getColumnIndexOrThrow(ChronicleDb.KEY_NAME)); long from = mCursor.getLong(mCursor.getColumnIndexOrThrow(ChronicleDb.KEY_FROM)); long to = mCursor.getLong(mCursor.getColumnIndexOrThrow(ChronicleDb.KEY_TO)); Log.i("ChronicleTaskList", id + ", "+ name+ ", "+ from+ ", "+to); flag = mCursor.moveToNext(); } String[] grpFromCols = { ChronicleDb.KEY_NAME}; int[] grpToVals = { R.id.cGroupRowTextName }; String[] fromCols = { TasksDbAdapter.KEY_TODODATE, TasksDbAdapter.KEY_NAME }; int[] toVals = { R.id.textViewDate2, R.id.taskRowTextTask }; ChronicleTreeListAdapterSimple adapter = new ChronicleTreeListAdapterSimple(this, mCursor, R.layout.c_group_row, grpFromCols, grpToVals, R.layout.task_row2, fromCols, toVals, true); expandableListView.setAdapter(adapter); The last line throws the exception. And the Adapter looks like this: public class ChronicleTreeListAdapterSimple extends SimpleCursorTreeAdapter { protected static String TAG = "ChronicleTreeListAdapter"; public ChronicleTreeListAdapterSimple( ChronicleTaskList context, Cursor cursor, int groupLayout, String[] groupFrom, int[] groupTo, int childLayout, String[] childFrom, int[] childTo, boolean showGroupName) { super(context, cursor, groupLayout, groupFrom, groupTo, childLayout, childFrom, childTo); taskList = context; }

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  • NullReferenceExeption when reading from a file

    - by Whitey
    I need to read a file structured like this: 01000 00030 00500 03000 00020 And put it in an array like this: int[,] iMap = new int[iMapHeight, iMapWidth] { {0, 1, 0, 0, 0}, {0, 0, 0, 3, 0}, {0, 0, 5, 0, 0}, {0, 3, 0, 0, 0}, {0, 0, 0, 2, 0}, }; Hopefully you see what I'm trying to do here. I was confused how to do this so I asked here on SO, but the code I got from it gets this error: Object reference not set to an instance of an object. I'm pretty new to this so I have no idea how to fix it... I only barely know the code: protected void ReadMap(string mapPath) { using (var reader = new StreamReader(mapPath)) { for (int i = 0; i < iMapHeight; i++) { string line = reader.ReadLine(); for (int j = 0; j < iMapWidth; j++) { iMap[i, j] = (int)(line[j] - '0'); } } } } The line I get the error on is this: iMap[i, j] = (int)(line[j] - '0'); Can anyone provide a solution? Thank you. :)

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  • optimize output value using a class and public member

    - by wiso
    Suppose you have a function, and you call it a lot of times, every time the function return a big object. I've optimized the problem using a functor that return void, and store the returning value in a public member: #include <vector> const int N = 100; std::vector<double> fun(const std::vector<double> & v, const int n) { std::vector<double> output = v; output[n] *= output[n]; return output; } class F { public: F() : output(N) {}; std::vector<double> output; void operator()(const std::vector<double> & v, const int n) { output = v; output[n] *= n; } }; int main() { std::vector<double> start(N,10.); std::vector<double> end(N); double a; // first solution for (unsigned long int i = 0; i != 10000000; ++i) a = fun(start, 2)[3]; // second solution F f; for (unsigned long int i = 0; i != 10000000; ++i) { f(start, 2); a = f.output[3]; } } Yes, I can use inline or optimize in an other way this problem, but here I want to stress on this problem: with the functor I declare and construct the output variable output only one time, using the function I do that every time it is called. The second solution is two time faster than the first with g++ -O1 or g++ -O2. What do you think about it, is it an ugly optimization?

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  • LINQ to XML - How to get Dictionary from Anonymous Object?

    - by DaveDev
    Currently I'm getting a list of HeaderColumns from the following XML snippet: <PerformancePanel> <HeaderColumns> <column performanceId="12" text="Over last month %" /> <column performanceId="13" text="Over last 3 months %" /> <column performanceId="16" text="1 Year %" /> <column performanceId="18" text="3 Years % p.a." /> <column performanceId="20" text="5 Years % p.a." /> <column performanceId="22" text="10 Years % p.a." /> </HeaderColumns> </PerformancePanel> from which I create an object as follows: (admitedly similar to an earlier question!) var performancePanels = new { Panels = (from panel in doc.Elements("PerformancePanel") select new { HeaderColumns = (from column in panel.Elements("HeaderColumns").Elements("column") select new { PerformanceId = (int)column.Attribute("performanceId"), Text = (string)column.Attribute("text") }).ToList(), }).ToList() }; I'd like if HeaderColumns was a Dictionary() so later I extract the values from the anonymous object like follows: Dictionary<int, string> myHeaders = new Dictionary<int, string>(); foreach (var column in performancePanels.Panels[0].HeaderColumns) { myHeaders.Add(column.PerformanceId, column.Text); } I thought I could achieve this with the Linq to XML with something similar to this HeaderColumns = (from column in panel.Elements("HeaderColumns").Elements("column") select new Dictionary<int, string>() { (int)column.Attribute("performanceId"), (string)column.Attribute("text") }).ToDictionary<int,string>(), but this doesn't work because ToDictionary() needs a Func parameter and I don't know what that is / how to implement it, and the code's probably wrong anyway! Could somebody please suggest how I can achieve the result I need? Thanks.

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  • Java for loop with multiple incrementers

    - by user2517280
    Im writing a program which combines the RGB pixel values for 3 images, e.g. red pixel of image 1, green pixel of image 2 and blue pixel of image 3 and I want to then create a final image of it. Im using the code below, but this seems to be incrementing x2 and x3 whilst x1 is the same, i.e. not giving the right pixel value for same co-ordinate for each image. for (int x = 0; x < image.getWidth(); x++) { for (int x2 = 0; x2 < image2.getWidth(); x2++) { for (int x3 = 0; x3 < image3.getWidth(); x3++) { for (int y = 0; y < image.getHeight(); y++) { for (int y2 = 0; y2 < image2.getHeight(); y2++) { for (int y3 = 0; y3 < image3.getHeight(); y3++) { So I was wondering if anyone can tell me how to iterate through each of the 3 images on the same co-ordinate, so for example read 1, 1 of each image and record the red, green and blue value accordingly. Apologies if it doesnt make complete sense, its a bit hard to explain. I can iterate the values for one image fine but when I add in another, things start to go a bit wrong as obviously its quite a bit more complicated! I was thinking it might be easier to create an array and replace the according values in that just not sure how to do that effectively either. Thanks

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  • Composing adaptors in Boost::range

    - by bruno nery
    I started playing with Boost::Range in order to have a pipeline of lazy transforms in C++]1. My problem now is how to split a pipeline in smaller parts. Suppose I have: int main(){ auto map = boost::adaptors::transformed; // shorten the name auto sink = generate(1) | map([](int x){ return 2*x; }) | map([](int x){ return x+1; }) | map([](int x){ return 3*x; }); for(auto i : sink) std::cout << i << "\n"; } And I want to replace the first two maps with a magic_transform, i.e.: int main(){ auto map = boost::adaptors::transformed; // shorten the name auto sink = generate(1) | magic_transform() | map([](int x){ return 3*x; }); for(auto i : sink) std::cout << i << "\n"; } How would one write magic_transform? I looked up Boost::Range's documentation, but I can't get a good grasp of it.

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  • c++ figuring out memory layout of members programatically

    - by anon
    Suppose in one program, I'm given: class Foo { int x; double y; char z; }; class Bar { Foo f1; int t; Foo f2; }; int main() { Bar b; bar.f1.z = 'h'; bar.f2.z = 'w'; ... some crap setting value of b; FILE *f = fopen("dump", "wb"); // c-style file fwrite(&b, sizeof(Bar), 1, f); } Suppose in another program, I have: int main() { File *f = fopen("dump", "rb"); std::string Foo = "int x; double y; char z;"; std::string Bar = "Foo f1; int t; Foo f2;"; // now, given this is it possible to read out // the value of bar.f1.z and bar.f2.z set earlier? } WHat I'm asking is: given I have the types of a class, can I figure out how C++ lays it out?

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  • Is this linear search implementation actually useful?

    - by Helper Method
    In Matters Computational I found this interesting linear search implementation (it's actually my Java implementation ;-)): public static int linearSearch(int[] a, int key) { int high = a.length - 1; int tmp = a[high]; // put a sentinel at the end of the array a[high] = key; int i = 0; while (a[i] != key) { i++; } // restore original value a[high] = tmp; if (i == high && key != tmp) { return NOT_CONTAINED; } return i; } It basically uses a sentinel, which is the searched for value, so that you always find the value and don't have to check for array boundaries. The last element is stored in a temp variable, and then the sentinel is placed at the last position. When the value is found (remember, it is always found due to the sentinel), the original element is restored and the index is checked if it represents the last index and is unequal to the searched for value. If that's the case, -1 (NOT_CONTAINED) is returned, otherwise the index. While I found this implementation really clever, I wonder if it is actually useful. For small arrays, it seems to be always slower, and for large arrays it only seems to be faster when the value is not found. Any ideas?

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  • unresolved token/symbol in MC++ wrapper class calling native code

    - by rediVider
    I'm new to MC++ and have basically no idea what's going on yet. In trying to get this working i've determined many things that don't work, i'm just looking for one of the ways that will work. I have a mc++ class as follows that seems to have to be a "ref" class to allow me to see any methods/properties. public ref class EmCeePlusPlus { static void Open(void) { Testor* t = new Testor(); Testor::Open(); }; }; extern public class Testor { public: Testor() { }; static void Open(void) { int x = 3; int xx = cli_lock(x); }; }; Now, the only reason i created the class Testor, and moved the call to cli_open to it, is because i was getting a unresolved external symbol if i put the same call in the ref class. In this current code, however, I get an uresolved token error and unresolved symbol error ONLY if i have the call to Testor::Open(). If that line is commented then it compiles fine. As it is I get the errors below. cli_lock() is native code that is able to be called externally by other native DLLs with not problems. Any ideas where i should be looking? error LNK2028: unresolved token (0A000056) "extern "C" int __cdecl cli_lock(int)" (?cli_lock@@$$J0YAHH@Z) referenced in function "public: static void __cdecl Giga::Testor::Open(void)" (?Open@Testor@Giga@@$$FSAXXZ) error LNK2019: unresolved external symbol "extern "C" int __cdecl cli_lock(int)" (?cli_lock@@$$J0YAHH@Z) referenced in function "public: static void __cdecl Giga::Testor::Open(void)" (?Open@Testor@Giga@@$$FSAXXZ)

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  • Problems with binding to Window Height and Width

    - by D.H.
    I have some problems when I try to bind the height and width of a window to properties in my view model. Here is a small sample app to illustrate the problem. This is the code in app.xaml.xs public partial class App : Application { protected override void OnStartup(StartupEventArgs e) { base.OnStartup(e); MainWindow mainWindow = new MainWindow(); MainWindowViewModel mainWindowViewModel = new MainWindowViewModel(); mainWindow.DataContext = mainWindowViewModel; mainWindow.Show(); } } This is MainWindow.xaml: <Window x:Class="TestApp.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Height="{Binding WindowHeight}" Width="{Binding WindowWidth}" BorderThickness="{Binding WindowBorderThickness}"> </Window> And this is the view model: public class MainWindowViewModel { public int WindowWidth { get { return 100; } } public int WindowHeight { get { return 200; } } public int WindowBorderThickness { get { return 8; } } } When the program is started the getters of WindowHeight and WindowBorderThickness (but not WindowWidth) are called, so the height and the border of the window is set properly, but not the width. I then add button that will trigger PropertyChanged for all properties, so that the view model now looks like this: public class MainWindowViewModel : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; public void TriggerPropertyChanges() { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs("WindowWidth")); PropertyChanged(this, new PropertyChangedEventArgs("WindowHeight")); PropertyChanged(this, new PropertyChangedEventArgs("WindowBorderThickness")); } } public ICommand ButtonCommand { get { return new RelayCommand(delegate { TriggerPropertyChanges(); }); } } public int WindowWidth { get { return 100; } } public int WindowHeight { get { return 200; } } public int WindowBorderThickness { get { return 8; } } } Now, when I click the button, the getter of WindowBorderThickness is called, but not the ones for WindowWidth and WindowHeight. It all just seems very weird and inconsistent to me. What am I missing?

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  • Is this mingw bug ?

    - by Debanjan
    Hi, I have been trying to execute this program on my migw ,through code::blocks, #include <string.h> #include <math.h> #include <stdio.h> #define N 100 int p[N / 64]; int pr[N]; int cnt; void sieve() { int i,j; for(i=0;i<N;i++) pr[i]=1; pr[0]=pr[1]=0; for(i=2;i<N;i++) if(pr[i]) { p[cnt]=i; cnt++; for(j=i+i;j<=N;j+=i) pr[j]=0; } } int main(){ sieve(); int i; for(i=0;i<cnt;i++) printf("%d ",p[i]); puts(""); printf("Total number of prime numbers : %d",cnt); return 0; } In My system the output is : 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 Total number of prime numbers : 22 Which is completely insane,since I am completely sure about the implementation of my algorithm. So I decided to try it in Ideone where it gives correct output.Can anybody point out the reason ?

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  • Time taken for memcpy decreases after certain point

    - by tss
    I ve a code which increases the size of the memory(identified by a pointer) exponentially. Instead of realloc, I use malloc followed by memcpy.. Something like this.. int size=5,newsize; int *c = malloc(size*sizeof(int)); int *temp; while(1) { newsize=2*size; //begin time temp=malloc(newsize*sizeof(int)); memcpy(temp,c,size*sizeof(int)); //end time //print time in mili seconds c=temp; size=newsize; } Thus the number of bytes getting copied is increasing exponentially. The time required for this task also increases almost linearly with the increase in size. However after certain point, the time taken abruptly reduces to a very small value and then remains constant. I recorded time for similar code, copyin data(Of my own type) 5 -> 10 - 2 ms 10 -> 20 - 2 ms . . 2560 -> 5120 - 5 ms . . 20480 -> 40960 - 30 ms 40960 -> 91920 - 58 ms 367680 -> 735360 - 2 ms 735360 -> 1470720 - 2 ms 1470720 -> 2941440 - 2 ms What is the reason for this drop in time ? Does a more optimal memcpy method get called when the size is large ?

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