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• Matrix multiplication using pairs

  - by sc_ray

  Hi, I am looking into alternate ways to do a Matrix Multiplication. Instead of storing my matrix as a two-dimensional array, I am using a vector such as vector<pair<pair<int,int >,int > > to store my matrix. The pair within my pair (pair) stores my indices (i,j) and the other int stores the value for the given (i,j) pair. I thought I might have some luck implementing my sparse array this way. The problem is when I try to multiply this matrix with itself. If this was a 2-d array implementation, I would have multiplied the matrix as follows: for(i=0; i<row1; i++) { for(j=0; j<col1; j++) { C[i][j] = 0; for(k=0; k<col2; k++) C[i][j] += A[i][j] * A[j][k]; } } Can somebody point out a way to achieve the same result using my vector of 'pair of pairs'? Thanks

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• How to take a collection of bytes and pull typed values out of it?

  - by Pat

  Say I have a collection of bytes var bytes = new byte[] {0, 1, 2, 3, 4, 5, 6, 7}; and I want to pull out a defined value from the bytes as a managed type, e.g. a ushort. What is a simple way to define what types reside at what location in the collection and pull out those values? One (ugly) way is to use System.BitConverter and a Queue or byte[] with an index and simply iterate through, e.g.: int index = 0; ushort first = System.BitConverter.ToUint16(bytes, index); index += 2; // size of a ushort int second = System.BitConverter.ToInt32(bytes, index); index += 4; ... This method gets very, very tedious when you deal with a lot of these structures! I know that there is the System.Runtime.InteropServices.StructLayoutAttribute which allows me to define the locations of types inside a struct or class, but there doesn't seem to be a way to import the collection of bytes into that struct. If I could somehow overlay the struct on the collection of bytes and pull out the values, that would be ideal. E.g. Foo foo = (Foo)bytes; // doesn't work because I'd need to implement the implicit operator ushort first = foo.first; int second = foo.second; ... [StructLayout(LayoutKind.Explicit, Size=FOO_SIZE)] public struct Foo { [FieldOffset(0)] public ushort first; [FieldOffset(2)] public int second; } Any thoughts on how to achieve this?

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• C/C++ I18N mbstowcs question

  - by bogertron

  I am working on internationalizing the input for a C/C++ application. I have currently hit an issue with converting from a multi-byte string to wide character string. The code needs to be cross platform compatible, so I am using mbstowcs and wcstombs as much as possible. I am currently working on a WIN32 machine and I have set the locale to a non-english locale (Japanese). When I attempt to convert a multibyte character string, I seem to be having some conversion issues. Here is an example of the code: int main(int argc, char** argv) { wchar_t *wcsVal = NULL; char *mbsVal = NULL; /* Get the current code page, in my case 932, runs only on windows */ TCHAR szCodePage[10]; int cch= GetLocaleInfo( GetSystemDefaultLCID(), LOCALE_IDEFAULTANSICODEPAGE, szCodePage, sizeof(szCodePage)); /* verify locale is set */ if (setlocale(LC_CTYPE, "") == 0) { fprintf(stderr, "Failed to set locale\n"); return 1; } mbsVal = argv[1]; /* validate multibyte string and convert to wide character */ int size = mbstowcs(NULL, mbsVal, 0); if (size == -1) { printf("Invalid multibyte\n"); return 1; } wcsVal = (wchar_t*) malloc(sizeof(wchar_t) * (size + 1)); if (wcsVal == NULL) { printf("memory issue \n"); return 1; } mbstowcs(wcsVal, szVal, size + 1); wprintf(L"%ls \n", wcsVal); return 0; } At the end of execution, the wide character string does not contain the converted data. I believe that there is an issue with the code page settings, because when i use MultiByteToWideChar and have the current code page sent in EX: MultiByteToWideChar( CP_ACP, 0, mbsVal, -1, wcsVal, size + 1 ); in place of the mbstowcs calls, the conversion succeeds. My question is, how do I use the generic mbstowcs call instead of teh MuliByteToWideChar call?

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• make arm architecture c library in mac

  - by gamegamelife

  I'm trying to make my own c library in Mac and include it to my iphone program. The c code is simple , like this: math.h: int myPow2(int); math.c: #include "math.h" int myPow2(int num) { return num*num; } I search how to make the c library file ( .a or .lib ..etc) seems need to use gcc compiler (Is there other methods?) so I use this command: gcc -c math.c -o math.o ar rcs libmath.a math.o And include it in iPhone Project. Now it has the problem when build xcode iphone project. "file was built for unsupported file format which is not the architecture being linked" I found some pages discuss about the problem, but no detail how to make the i386/arm architecture library. And I finally use this command to do it: gcc -arch i386 -c math.c -o math.o /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/arm-apple-darwin10-gcc-4.2.1 -c math.c -o math.o I dont know if this method is correct? Or there has another method to do it?

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• onItemClick gives index/ position of item on visible page ... not actual index of the item in list .

  - by Abhinav

  hi, I am creating a list .. the elements of the list are drawn from sqlite database .. I populate the list using ArrayList and ArrayAdapter ...upon clicking the items on the list I want to be able to fire an intent containing info about the item clicked ... info like the index number of the item .. using the method : onItemClick(AdapterView av, View v, int index, long arg) I do get index of the item clicked . however it is of the list currently displayed . the problem comes when I do setFilterTextEnabled(true) , and on the app type in some text to to search some item ..and then click it ..rather than giving me the index of the item on the original list it gives me the index on filtered list.. following is the snippet of code: myListView.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> av, View v, int index, long arg) { Intent lyricsViewIntent = new Intent(iginga.this, LyricsPage.class); lyricsViewIntent.putExtra("title", songList.get((int)arg).getTitle()); lyricsViewIntent.putExtra("id", songList.get((int)arg).getSongId()); startActivity(lyricsViewIntent); } }); myListView.setTextFilterEnabled(true); Is there any way I can get the original index /position of the item instead of the one showing in filtered text ...when filtered.

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• Preprocessor #define vs. function pointer - best practice?

  - by Dustin

  I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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• SQL left join with multiple rows into one row

  - by beardedd

  Basically, I have two tables, Table A contains the actual items that I care to get out, and Table B is used for language translations. So, for example, Table A contains the actual content. Anytime text is used within the table, instead of storing actual varchar values, ids are stored that relate back to text stored in Table B. This allows me to by adding a languageID column to Table B, have multiple translations for the same row in the database. Example: Table A Title (int) Description (int) Other Data.... Table B TextID (int) - This is the column whose value is stored in other tables LanguageID (int) Text (varchar) My question is more a call for suggestions on how to best handle this. Ideally I want a query that I can use to select from the table, and get the text as opposed to the ids of the text out of the table. Currently when I have two text items in the table this is what I do: SELECT C.ID, C.Title, D.Text AS Description FROM (SELECT A.ID, A.Description, B.Text AS Title FROM TableA A, TranslationsTable B WHERE A.Title = B.TextID AND B.LanguaugeID = 1) C LEFT JOIN TranslationsTable D ON C.Description = D.TextID AND D.LanguaugeID = 1 This query gives me the row from Table A I am looking for (using where statements in the inner select statement) with the actual text based on the language ID used instead of the text ids. This works fine when I am only using one or two text items that need to be translated, but adding a third item or more, it starts to get really messy - essentially another left join on top of the example. Any suggestions on a better query, or at least a good way to handle 3 or more text items in a single row?

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• How do you hide a Swing Popup when you click somewhere else.

  - by Casey Watson

  I have a Popup that is shown when a user clicks on a button. I would like to hide the popup when any of the following events occur: The user clicks somewhere else in the application. (The background panel for example) The user minimizes the application. The JPopupMenu has this behavior, but I need more than just JMenuItems. The following code block is a simplified illustration to demonstrate the current usage. import java.awt.*; import java.awt.event.ActionEvent; import javax.swing.*; public class PopupTester extends JFrame { public static void main(String[] args) { final PopupTester popupTester = new PopupTester(); popupTester.setLayout(new FlowLayout()); popupTester.setSize(300, 100); popupTester.add(new JButton("Click Me") { @Override protected void fireActionPerformed(ActionEvent event) { Point location = getLocationOnScreen(); int y = (int) (location.getY() + getHeight()); int x = (int) location.getX(); JLabel myComponent = new JLabel("Howdy"); Popup popup = PopupFactory.getSharedInstance().getPopup(popupTester, myComponent, x, y); popup.show(); } }); popupTester.add(new JButton("No Click Me")); popupTester.setVisible(true); popupTester.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } }

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• C++ variable to const expression

  - by user1344784

  template <typename Real> class A{ }; template <typename Real> class B{ }; //... a few dozen more similar template classes class Computer{ public slots: void setFrom(int from){ from_ = from; } void setTo(int to){ to_ = to; } private: template <int F, int T> void compute(){ using boost::fusion::vector; using boost::fusion::at_c; vector<A<float>, B<float>, ...> v; at_c<from_>(v).operator()(at_c<to_>(v)); //error; needs to be const-expression. }; This question isn't about Qt, but there is a line of Qt code in my example. The setFrom() and setTo() are functions that are called based on user selection via the GUI widget. The root of my problem is that 'from' and 'to' are variables. In my compute member function I need to pick a type (A, B, etc.) based on the values of 'from' and 'to'. The only way I know how to do what I need to do is to use switch statements, but that's extremely tedious in my case and I would like to avoid. Is there anyway to convert the error line to a constant-expression?

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• java label setText and setBounds clashing?

  - by java

  I would like to have a JLabel changint color to a random one, while jumping to a random position, and while changing its text. but the setText and setBounds seem to clash and i don't know why. if you comment out the setText then the setBounds will work, but they won't work together. import java.awt.*; import java.util.*; import javax.swing.*; public class test2 extends JFrame { private static JLabel label = new JLabel("0"); private static Random gen = new Random(); public test2() { JPanel panel = new JPanel(); panel.add(label); this.add(panel); } public static void move() { for (int i = 0; i < 10; i++) { int n = gen.nextInt(254)+1; int nn = gen.nextInt(254)+1; int nnn = gen.nextInt(254)+1; label.setText(""+i); //the setBounds command will not work with the setText command. why? label.setBounds(n*2, nn*2, 20, 20); label.setForeground(new Color(n, nn, nnn)); try { Thread.sleep(200); } catch (Exception e) {} } } public static void main(String[] args) { test2 frame = new test2(); frame.setVisible(true); frame.setSize(600, 600); frame.setResizable(true); frame.setLocationRelativeTo(null); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); move(); } }

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• Fast serialization/deserialization of structs

  - by user256890

  I have huge amont of geographic data represented in simple object structure consisting only structs. All of my fields are of value type. public struct Child { readonly float X; readonly float Y; readonly int myField; } public struct Parent { readonly int id; readonly int field1; readonly int field2; readonly Child[] children; } The data is chunked up nicely to small portions of Parent[]-s. Each array contains a few thousands Parent instances. I have way too much data to keep all in memory, so I need to swap these chunks to disk back and forth. (One file would result approx. 2-300KB). What would be the most efficient way of serializing/deserializing the Parent[] to a byte[] for dumpint to disk and reading back? Concerning speed, I am particularly interested in fast deserialization, write speed is not that critical. Would simple BinarySerializer good enough? Or should I hack around with StructLayout (see accepted answer)? I am not sure if that would work with array field of Parent.children. UPDATE: Response to comments - Yes, the objects are immutable (code updated) and indeed the children field is not value type. 300KB sounds not much but I have zillions of files like that, so speed does matter.

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• Java Applet 411 Content Length

  - by user1903006

  I am new to Java. I wrote an applet with a gui that sends results (int w and int p) to a server, and I get the "411 Length Required" error. What am I doing wrong? How do you set a Content-Length? This is the method that communicates with the server: public void sendPoints1(int w, int p){ try { String url = "http://somename.com:309/api/Results"; String charset = "UTF-8"; String query = String.format("?key=%s&value=%s", URLEncoder.encode(String.valueOf(w), charset), URLEncoder.encode(String.valueOf(p), charset)); String length = String.valueOf((url + query).getBytes("UTF-8").length); HttpURLConnection connection = (HttpURLConnection) new URL(url + query).openConnection(); connection.setRequestMethod("POST"); connection.setRequestProperty("Content-Length", length); connection.connect(); System.out.println("Responce Code: " + connection.getResponseCode()); System.out.println("Responce Message: " + connection.getResponseMessage()); } catch (Exception e) { System.err.println(e.getMessage()); } }

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• Why `is_base_of` works with private inheritance?

  - by Alexey Malistov

  Why the following code works? typedef char (&yes)[1]; typedef char (&no)[2]; template <typename B, typename D> struct Host { operator B*() const; operator D*(); }; template <typename B, typename D> struct is_base_of { template <typename T> static yes check(D*, T); static no check(B*, int); static const bool value = sizeof(check(Host<B,D>(), int())) == sizeof(yes); }; //Test sample class B {}; class D : private B {}; //Exspression is true. int test[is_base_of<B,D>::value && !is_base_of<D,B>::value]; Note that B is private base. Note that operator B*() is const. How does this work? Why this works? Why static yes check(D*, T); is better than static yes check(B*, int); ?

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• How to "wrap" implementation in C#

  - by igor

  Hello, I have these classes in C# (.NET Framework 3.5) described below: public class Base { public int State {get; set;} public virtual int Method1(){} public virtual string Method2(){} ... public virtual void Method10(){} } public class B: Base { // some implementation } public class Proxy: Base { private B _b; public class Proxy(B b) { _b = b; } public override int Method1() { if (State == Running) return _b.Method1(); else return base.Method1(); } public override string Method2() { if (State == Running) return _b.Method2(); else return base.Method2(); } public override void Method10() { if (State == Running) _b.Method10(); else base.Method10(); } } I want to get something this: public Base GetStateDependentImplementation() { if (State == Running) // may be some other rule return _b; else return base; // compile error } and my Proxy's implementation will be: public class Proxy: Base { ... public override int Method1() { return GetStateDependentImplementation().Method1(); } public override string Method2() { return GetStateDependentImplementation().Method2(); } ... } Of course, I can do this (aggregation of base implementation): public RepeaterOfBase: Base // no any overrides, just inheritance { } public class Proxy: Base { private B _b; private RepeaterOfBase _Base; public class Proxy(B b, RepeaterOfBase aBase) { _b = b; _base = aBase; } } ... public Base GetStateDependentImplementation() { if (State == Running) return _b; else return _Base; } ... But instance of Base class is very huge and I have to avoid to have other additional copy in memory. So I have to simplify my code have to "wrap" implementation have to avoid a code duplication have to avoid aggregation of any additional instance of Base class (duplication) Is it possible to reach these goals?

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• fgets throwing unhandled exception while parsing stl

  - by user3478400

  I am new to c++, I am trying to parse a stl file which is of about 64MB and has about ~18K lines in it. The code works fine for first few 100 lines but then fgets throws following exception: "Unhandled exception at 0x77B0BAC5 (ntdll.dll) in STLparser.exe: 0xC0000024: There is a mismatch between the type of object required by the requested operation and the type of object that is specified in the request." I have checked manually the line for which fgets throws exception, there is nothing out of ordinary there. I am out of options for now. Any help to fix this issue will be greatly appreciated. ================CODE========================== #include<fstream> #include<iostream> #include"ParseString.h" #include"Vectors.h" using namespace std; int main(void) { //Define variables FILE *file; char *line = new char; parsestring oneline; int n_Vols = 0, n_Elms = 0, n_nods = -1, E = 0; Nod *nodes = new Nod(); Nod dummy; Elm *elements = new Elm(); int mycounter = 0; //Open file fopen_s(&file, "sample.stl", "r"); while (fgets(line, 1024, file) != NULL) //**********Getting Error Here************* { // populate required data } fclose(file); printf("%d,%d,%d", n_Vols, n_Elms, n_nods); getchar(); return 0; } ===================When broken, execution resumes at this function (not my function, something internal) void __cdecl _unlock ( int locknum ) { /* * leave the critical section. */ LeaveCriticalSection( _locktable[locknum].lock ); }

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• How to detect the root recursive call?

  - by ahmadabdolkader

  Say we're writing a simple recursive function fib(n) that calculates the nth Fibonacci number. Now, we want the function to print that nth number. As the same function is being called repeatedly, there has to be a condition that allows only the root call to print. The question is: how to write this condition without passing any additional arguments, or using global/static variables. So, we're dealing with something like this: int fib(int n) { if(n <= 0) return 0; int fn = 1; if(n > 2) fn = fib(n-2) + fib(n-1); if(???) cout << fn << endl; return fn; } int main() { fib(5); return 0; } I thought that the root call differs from all children by returning to a different caller, namely the main method in this example. I wanted to know whether it is possible to use this property to write the condition and how. Update: please note that this is a contrived example that only serves to present the idea. This should be clear from the tags. I'm not looking for standard solutions. Thanks.

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• Modeling many-to-one with constraints?

  - by Greg Beech

  I'm attempting to create a database model for movie classifications, where each movie could have a single classification from each of one of multiple rating systems (e.g. BBFC, MPAA). This is the current design, with all implied PKs and FKs: TABLE Movie ( MovieId INT ) TABLE ClassificationSystem ( ClassificationSystemId TINYINT ) TABLE Classification ( ClassificationId INT, ClassificationSystemId TINYINT ) TABLE MovieClassification ( MovieId INT, ClassificationId INT, Advice NVARCHAR(250) -- description of why the classification was given ) The problem is with the MovieClassification table whose constraints would allow multiple classifications from the same system, whereas it should ideally only permit either zero or one classifications from a given system. Is there any reasonable way to restructure this so that a movie having exactly zero or one classifications from any given system is enforced by database constraints, given the following requirements? Do not duplicate information that could be looked up (i.e. duplicating ClassificationSystemId in the MovieClassification table is not a good solution because this could get out of sync with the value in the Classification table) Remain extensible to multiple classification systems (i.e. a new classification system does not require any changes to the table structure)? Note also the Advice column - each mapping of a movie to a classification needs to have a textual description of why that classification was given to that movie. Any design would need to support this.

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• std::ifstream buffer caching

  - by ledokol

  Hello everybody, In my application I'm trying to merge sorted files (keeping them sorted of course), so I have to iterate through each element in both files to write the minimal to the third one. This works pretty much slow on big files, as far as I don't see any other choice (the iteration has to be done) I'm trying to optimize file loading. I can use some amount of RAM, which I can use for buffering. I mean instead of reading 4 bytes from both files every time I can read once something like 100Mb and work with that buffer after that, until there will be no element in buffer, then I'll refill the buffer again. But I guess ifstream is already doing that, will it give me more performance and is there any reason? If fstream does, maybe I can change size of that buffer? added My current code looks like that (pseudocode) // this is done in loop int i1 = input1.read_integer(); int i2 = input2.read_integer(); if (!input1.eof() && !input2.eof()) { if (i1 < i2) { output.write(i1); input2.seek_back(sizeof(int)); } else input1.seek_back(sizeof(int)); output.write(i2); } } else { if (input1.eof()) output.write(i2); else if (input2.eof()) output.write(i1); } What I don't like here is seek_back - I have to seek back to previous position as there is no way to peek 4 bytes too much reading from file if one of the streams is in EOF it still continues to check that stream instead of putting contents of another stream directly to output, but this is not a big issue, because chunk sizes are almost always equal. Can you suggest improvement for that? Thanks.

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• How to specify generic method type parameters partly

  - by DNNX

  I have an extension method like below: public static T GetValueAs<T, R>(this IDictionary<string, R> dictionary, string fieldName) where T : R { R value; if (!dictionary.TryGetValue(fieldName, out value)) return default(T); return (T)value; } Currently, I can use it in the following way: var dictionary = new Dictionary<string, object(); //... var list = dictionary.GetValueAs<List<int, object("A"); // this may throw ClassCastException - this is expected behavior; It works pretty fine, but the second type parameter is really annoying. Is it possible in C# 4.0 rewrite GetValueAs is such a way that the method will still be applicable to different types of string-keyed dictionaries AND there will be no need to specify second type parameter in the calling code, i.e. use var list = dictionary.GetValueAs<List<int("A"); or at least something like var list = dictionary.GetValueAs<List<int, ?("A"); instead of var list = dictionary.GetValueAs<List<int, object("A");

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• How can show data from another form

  - by Michael Quiles

  This is basically a tic tac toe game, and I have another form called Winner.cs when a player wins I want it to call the form (this part works) and then I want it to say xWinner.label =b1.text"" + has won the game!. the part I cant get to work is displaying the text in the winners form label. There's an example of a message box that commented out for reference instead of b1.text using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows.Forms; namespace MyGame { public class Result1 { static private int[,] Winners = new int[,] { {0,1,2}, {3,4,5}, {6,7,8}, {0,3,6}, {1,4,7}, {2,5,8}, {0,4,8}, {2,4,6}, }; static public bool CheckWinner(Button[] myControls) { bool gameOver = false; for (int i = 0; i < 8; i++) { int a = Winners[i, 0], b = Winners[i, 1], c = Winners[i, 2]; Button b1 = myControls[a], b2 = myControls[b], b3 = myControls[c]; if (b1.Text == "" || b2.Text == "" || b3.Text == "") continue; if (b1.Text == b2.Text && b2.Text == b3.Text) { b1.BackColor = b2.BackColor = b3.BackColor = System.Drawing.Color.LightCoral; b1.Font = b2.Font = b3.Font = new System.Drawing.Font("Microsoft Sans Serif", 32F, System.Drawing.FontStyle.Italic & System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0))); gameOver = true; Form xWinnerForm = new xWinnerForm(); xWinnerForm.Show(); //MessageBox.Show(b1.Text + " .... Wins the game!", "Game End", MessageBoxButtons.OK); //break; } } return gameOver; } } }

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• Another boost error

  - by user1676605

  On this code I get the enourmous error static void ParseTheCommandLine(int argc, char *argv[]) { int count; int seqNumber; namespace po = boost::program_options; std::string appName = boost::filesystem::basename(argv[0]); po::options_description desc("Generic options"); desc.add_options() ("version,v", "print version string") ("help", "produce help message") ("sequence-number", po::value<int>(&seqNumber)->default_value(0), "sequence number") ("pem-file", po::value< vector<string> >(), "pem file") ; po::positional_options_description p; p.add("pem-file", -1); po::variables_map vm; po::store(po::command_line_parser(argc, argv). options(desc).positional(p).run(), vm); po::notify(vm); if (vm.count("pem file")) { cout << "Pem files are: " << vm["pem-file"].as< vector<string> >() << "\n"; } cout << "Sequence number is " << seqNumber << "\n"; exit(1); ../../../FIXMarketDataCommandLineParameters/FIXMarketDataCommandLineParameters.hpp|98|error: no match for ‘operator<<’ in ‘std::operator<< [with _Traits = std::char_traits](((std::basic_ostream &)(& std::cout)), ((const char*)"Pem files are: ")) << ((const boost::program_options::variable_value*)vm.boost::program_options::variables_map::operator[](((const std::string&)(& std::basic_string, std::allocator (((const char*)"pem-file"), ((const std::allocator&)((const std::allocator*)(& std::allocator()))))))))-boost::program_options::variable_value::as with T = std::vector, std::allocator , std::allocator, std::allocator ’|

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• How to access the element of a list/vector that passed by reference in C++

  - by bsoundra

  Hi all, The problem is passing lists/vectors by reference int main(){ list<int> arr; //Adding few ints here to arr func1(&arr); return 0; } void func1(list<int> * arr){ // How Can I print the values here ? //I tried all the below , but it is erroring out. cout<<arr[0]; // error cout<<*arr[0];// error cout<<(*arr)[0];//error //How do I modify the value at the index 0 ? func2(arr);// Since it is already a pointer, I am passing just the address } void func2(list<int> *arr){ //How do I print and modify the values here ? I believe it should be the same as above but // just in case. } Is the vectors any different from the lists ? Thanks in advance. Any links where these things are explained elaborately will be of great help. Thanks again.

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• Can someone please explain Cursor in android ?

  - by Prabhat

  Can some one explain how the cursor exactly works ? Or the flow of the following part of the code ? I know that this is sub activity and all but I did not understand how Cursor works exactly. final Uri data = Uri.parse("content://contacts/people/"); final Cursor c = managedQuery(data, null, null, null, null); String[] from = new String[] { People.NAME }; int[] to = new int[] { R.id.itemTextView }; SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,R.layout.listitemlayout, c, from, to); ListView lv = (ListView) findViewById(R.id.contactListView); lv.setAdapter(adapter); lv.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int pos, long id) { c.moveToPosition(pos); int rowId = c.getInt(c.getColumnIndexOrThrow("_id")); Uri outURI = Uri.parse(data.toString() + rowId); Intent outData = new Intent(); outData.setData(outURI); setResult(Activity.RESULT_OK, outData); finish(); } }); Thanks.

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• Problem with reading and writing to binary file in C++

  - by Reem

  I need to make a file that contains "name" which is a string -array of char- and "data" which is array of bytes -array of char in C++- but the first problem I faced is how to separate the "name" from the "data"? newline character could work in this case (assuming that I don't have "\n" in the name) but I could have special characters in the "data" part so there's no way to know when it ends so I'm putting an int value in the file before the data which has the size of the "data"! I tried to do this with code as follow: if((fp = fopen("file.bin","wb")) == NULL) { return false; } char buffer[] = "first data\n"; fwrite( buffer ,1,sizeof(buffer),fp ); int number[1]; number[0]=10; fwrite( number ,1,1, fp ); char data[] = "1234567890"; fwrite( data , 1, number[0], fp ); fclose(fp); but I didn't know if the "int" part was right, so I tried many other codes including this one: char buffer[] = "first data\n"; fwrite( buffer ,1,sizeof(buffer),fp ); int size=10; fwrite( &size ,sizeof size,1, fp ); char data[] = "1234567890"; fwrite( data , 1, number[0], fp ); I see 4 "NULL" characters in the file when I open it instead of seeing an integer. Is that normal? The other problem I'm facing is reading that again from the file! The code I tried to read didn't work at all :( I tried it with "fread" but I'm not sure if I should use "fseek" with it or it just read the other character after it. Forgive me but I'm a beginner :(

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• Know the row with max characters (C)

  - by l_core

  I have wrote a program in C, to find the row with the max number of characters. Here is the code #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <string.h> int main (int argc, char *argv[]) { char c; /* used to store the character with getc */ int c_tot = 0, c_rig = 0, c_max = 0; /* counters of characters*/ int r_tot = 0; /* counters of rows */ FILE *fptr; fptr = fopen(argv[1], "r"); if (fptr == NULL || argc != 2) { printf ("Error opening the file %s\n'", argv[1]); exit(EXIT_FAILURE); } while ( (c = getc(fptr)) != EOF) { if (c != ' ' && c != '\n') { c_tot++; c_rig++; } if (c == '\n') { r_tot++; if (c_rig > c_max) c_max = c_rig; c_rig = 0; } } printf ("Total rows: %d\n", r_tot); printf ("Total characters: %d\n", c_tot); printf ("Total characters in a row: %d\n", c_max); printf ("Average number of characters on a row: %d\n", (c_tot/r_tot)); printf ("The row with max characters is: %s\n", ??????) return 0; } I can easily find the row with the highest number of characters but how can i print that out? Thank You Folks

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