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  • Can a member struct be zero-init from the constructor initializer list without calling memset?

    - by selbie
    Let's say I have the following structure declaration (simple struct with no constructor). struct Foo { int x; int y; int z; char szData[DATA_SIZE]; }; Now let's say this struct is a member of a C++ class as follows: class CFoobar { Foo _foo; public: CFoobar(); }; If I declare CFoobar's constructor as follows: CFoobar::CFoobar() { printf("_foo = {%d, %d, %d}\n", _foo.x, _foo.y,_foo.z); for (int x = 0; x < 100; x++) printf("%d\n", _foo.szData[x]); } As you would expect, when CFoobar's constructor runs, garbage data gets printed out Obviously, the easy fix is to memset or ZeroMemory &_foo. It's what I've always done... However, I did notice that if add _foo to the constructor's initialization list with no parameters as follows: CFoobar::CFoobar() : _foo() { That this appears to zero-out the member variables of _foo. At least that was the case with g++ on linux. Now here's my question: Is this standard C++, or is this compiler specific behavior? If it's standard behavior, can someone quote me a reference from an official source? Any "gotchas" in regards to implicit zero-init behavior with more complicated structs and classes?

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  • Saving image to server with php

    - by salmon
    Hey i have the following script, basicaly a flash file sends it some data and it creates a image and then opens a save as dialog box for the user so that they can save the image to there system.Here the problem comes in, how would i go about also saving the image to my server? <?php $to = $_POST['to']; $from = $_POST['from']; $fname = $_POST['fname']; $send = $_POST['send']; $data = explode(",", $_POST['img']); $width = $_POST['width']; $height = $_POST['height']; $image=imagecreatetruecolor( $width ,$height ); $background = imagecolorallocate( $image ,0 , 0 , 0 ); //Copy pixels $i = 0; for($x=0; $x<=$width; $x++){ for($y=0; $y<=$height; $y++){ $int = hexdec($data[$i++]); $color = ImageColorAllocate ($image, 0xFF & ($int >> 0x10), 0xFF & ($int >> 0x8), 0xFF & $int); imagesetpixel ( $image , $x , $y , $color ); } } //Output image and clean #header("Content-Disposition: attachment; filename=test.jpg" ); header("Content-type: image/jpeg"); ImageJPEG( $image ); imagedestroy( $image ); ?> Help would be greatly appreciated!

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  • Different output between release and Debug

    - by AthomSfere
    I can't figure this one out. I have a c++ Application that works in Debug mode exactly as expected: #include "stdafx.h" #include <string> #include <Windows.h> #include <iostream> using namespace std; void truncateServer(std::string inString); int _tmain(int argc, char *argv[]) { char* server = argv[1]; truncateServer(server); } void truncateServer(std::string inString) { std::string server = ""; int whackCount = 0; for (unsigned int i = 0; i < inString.length(); i++) { char c = inString[i]; if (whackCount < 3) { if (c == '\\') whackCount++; else server += c; } } cout << server; } For example if I call the server I want via its UNC path \\serverName\Share\ in the debug it gives me exactly what I want: servername However, if I use the release build I get nothing: I deleted the release output folder, but the issue is exactly the same. I can only assume there is some other difference between the release and build applications that is exposing a major issue with my code? Or another difference between the outputs I need to account for. What do I need to do to get the expected output?

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  • Need some help understanding a weird C behavior

    - by mike
    This part of my code works fine: #include <stdio.h> int main(){ //char somestring[3] = "abc"; int i, j; int count = 5; for((i=0) && (j=0); count > 0; i++ && j++){ printf("i = %d and j = %d\n", i, j); count--; } return 0; } The output as expected: i : 0 and j : 0 i : 1 and j : 1 i : 2 and j : 2 i : 3 and j : 3 i : 4 and j : 4 Things get weird when I uncomment the char string declaration on the first line of the function body. #include <stdio.h> int main(){ char somestring[3] = "abc"; ... } The output: i : 0 and j : 4195392 i : 1 and j : 4195393 i : 2 and j : 4195394 i : 3 and j : 4195395 i : 4 and j : 4195396 What's the logic behind this? I'm using gcc 4.4.1 on Ubuntu 9.10.

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  • A question on getting number of nodes in a Binary Tree

    - by Robert
    Dear all, I have written up two functions (pseudo code) for calculation the number of nodes and the tree height of a Binary Tree,given the root of the tree. Most importantly,the Binary Tree is represented as the First chiled/next sibling format. so struct TreeNode { Object element; TreeNode *firstChild; TreeNode *nextSibling; } Calculate the # of nodes: public int countNode(TreeNode root) { int count=0; while(root!=null) { root= root.firstChild; count++; } return count; } public int countHeight(TreeNode root) { int height=0; while(root!=null) { root= root.nextSibling; height++; } return height; } This is one of the problem I saw on an algorithm book,and my solution above seems to have some problems,also I didn't quite get the points of using this First Child/right sibling representation of Binary Tree,could you guys give me some idea and feedback,please? Cheers!

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  • Database Tutorial: The method open() is undefined for the type MainActivity.DBAdapter

    - by user2203633
    I am trying to do this database tutorial on SQLite Eclipse: https://www.youtube.com/watch?v=j-IV87qQ00M But I get a few errors at the end.. at db.ppen(); i get error: The method open() is undefined for the type MainActivity.DBAdapter and similar for insert record and close. MainActivity: package com.example.studentdatabase; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import android.app.Activity; import android.app.ListActivity; import android.content.Intent; import android.database.Cursor; import android.os.Bundle; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.Button; import android.widget.Toast; public class MainActivity extends Activity { /** Called when the activity is first created. */ //DBAdapter db = new DBAdapter(this); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button addBtn = (Button)findViewById(R.id.add); addBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Intent i = new Intent(MainActivity.this, addassignment.class); startActivity(i); } }); try { String destPath = "/data/data/" + getPackageName() + "/databases/AssignmentDB"; File f = new File(destPath); if (!f.exists()) { CopyDB( getBaseContext().getAssets().open("mydb"), new FileOutputStream(destPath)); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } DBAdapter db = new DBAdapter(); //---add an assignment--- db.open(); long id = db.insertRecord("Hello World", "2/18/2012", "DPR 224", "First Android Project"); id = db.insertRecord("Workbook Exercises", "3/1/2012", "MAT 100", "Do odd numbers"); db.close(); //---get all Records--- /* db.open(); Cursor c = db.getAllRecords(); if (c.moveToFirst()) { do { DisplayRecord(c); } while (c.moveToNext()); } db.close(); */ /* //---get a Record--- db.open(); Cursor c = db.getRecord(2); if (c.moveToFirst()) DisplayRecord(c); else Toast.makeText(this, "No Assignments found", Toast.LENGTH_LONG).show(); db.close(); */ //---update Record--- /* db.open(); if (db.updateRecord(1, "Hello Android", "2/19/2012", "DPR 224", "First Android Project")) Toast.makeText(this, "Update successful.", Toast.LENGTH_LONG).show(); else Toast.makeText(this, "Update failed.", Toast.LENGTH_LONG).show(); db.close(); */ /* //---delete a Record--- db.open(); if (db.deleteRecord(1)) Toast.makeText(this, "Delete successful.", Toast.LENGTH_LONG).show(); else Toast.makeText(this, "Delete failed.", Toast.LENGTH_LONG).show(); db.close(); */ } private class DBAdapter extends BaseAdapter { private LayoutInflater mInflater; //private ArrayList<> @Override public int getCount() { return 0; } @Override public Object getItem(int arg0) { return null; } @Override public long getItemId(int arg0) { return 0; } @Override public View getView(int arg0, View arg1, ViewGroup arg2) { return null; } } public void CopyDB(InputStream inputStream, OutputStream outputStream) throws IOException { //---copy 1K bytes at a time--- byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) > 0) { outputStream.write(buffer, 0, length); } inputStream.close(); outputStream.close(); } public void DisplayRecord(Cursor c) { Toast.makeText(this, "id: " + c.getString(0) + "\n" + "Title: " + c.getString(1) + "\n" + "Due Date: " + c.getString(2), Toast.LENGTH_SHORT).show(); } public void addAssignment(View view) { Intent i = new Intent("com.pinchtapzoom.addassignment"); startActivity(i); Log.d("TAG", "Clicked"); } } DBAdapter code: package com.example.studentdatabase; public class DBAdapter { public static final String KEY_ROWID = "id"; public static final String KEY_TITLE = "title"; public static final String KEY_DUEDATE = "duedate"; public static final String KEY_COURSE = "course"; public static final String KEY_NOTES = "notes"; private static final String TAG = "DBAdapter"; private static final String DATABASE_NAME = "AssignmentsDB"; private static final String DATABASE_TABLE = "assignments"; private static final int DATABASE_VERSION = 2; private static final String DATABASE_CREATE = "create table if not exists assignments (id integer primary key autoincrement, " + "title VARCHAR not null, duedate date, course VARCHAR, notes VARCHAR );"; private final Context context; private DatabaseHelper DBHelper; private SQLiteDatabase db; public DBAdapter(Context ctx) { this.context = ctx; DBHelper = new DatabaseHelper(context); } private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { try { db.execSQL(DATABASE_CREATE); } catch (SQLException e) { e.printStackTrace(); } } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS contacts"); onCreate(db); } } //---opens the database--- public DBAdapter open() throws SQLException { db = DBHelper.getWritableDatabase(); return this; } //---closes the database--- public void close() { DBHelper.close(); } //---insert a record into the database--- public long insertRecord(String title, String duedate, String course, String notes) { ContentValues initialValues = new ContentValues(); initialValues.put(KEY_TITLE, title); initialValues.put(KEY_DUEDATE, duedate); initialValues.put(KEY_COURSE, course); initialValues.put(KEY_NOTES, notes); return db.insert(DATABASE_TABLE, null, initialValues); } //---deletes a particular record--- public boolean deleteContact(long rowId) { return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0; } //---retrieves all the records--- public Cursor getAllRecords() { return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_TITLE, KEY_DUEDATE, KEY_COURSE, KEY_NOTES}, null, null, null, null, null); } //---retrieves a particular record--- public Cursor getRecord(long rowId) throws SQLException { Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, KEY_TITLE, KEY_DUEDATE, KEY_COURSE, KEY_NOTES}, KEY_ROWID + "=" + rowId, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; } //---updates a record--- public boolean updateRecord(long rowId, String title, String duedate, String course, String notes) { ContentValues args = new ContentValues(); args.put(KEY_TITLE, title); args.put(KEY_DUEDATE, duedate); args.put(KEY_COURSE, course); args.put(KEY_NOTES, notes); return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0; } } addassignment code: package com.example.studentdatabase; public class addassignment extends Activity { DBAdapter db = new DBAdapter(this); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.add); } public void addAssignment(View v) { Log.d("test", "adding"); //get data from form EditText nameTxt = (EditText)findViewById(R.id.editTitle); EditText dateTxt = (EditText)findViewById(R.id.editDuedate); EditText courseTxt = (EditText)findViewById(R.id.editCourse); EditText notesTxt = (EditText)findViewById(R.id.editNotes); db.open(); long id = db.insertRecord(nameTxt.getText().toString(), dateTxt.getText().toString(), courseTxt.getText().toString(), notesTxt.getText().toString()); db.close(); nameTxt.setText(""); dateTxt.setText(""); courseTxt.setText(""); notesTxt.setText(""); Toast.makeText(addassignment.this,"Assignment Added", Toast.LENGTH_LONG).show(); } public void viewAssignments(View v) { Intent i = new Intent(this, MainActivity.class); startActivity(i); } } What is wrong here? Thanks in advance.

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  • Exposing a C++ API to C#

    - by Siyfion
    So what I have is a C++ API contained within a *.dll and I want to use a C# application to call methods within the API. So far I have created a C++ / CLR project that includes the native C++ API and managed to create a "bridge" class that looks a bit like the following: ManagedBridge.h namespace ManagedAPIWrapper { public ref class Bridge { public: int bridge_test(void); int bridge_test2(api_struct* temp); } } ManagedBridge.cpp int Bridge::bridge_test(void) { return test(); } int Bridge::bridge_test2(api_struct* temp) { return test2(temp); } I also have a C# application that has a reference to the C++/CLR "Bridge.dll" and then uses the methods contained within. I have a number of problems with this: I can't figure out how to call bridge_test2 within the C# program, as it has no knowledge of what a api_struct actually is. I know that I need to marshal the object somewhere, but do I do it in the C# program or the C++/CLR bridge? This seems like a very long-winded way of exposing all of the methods in the API, is there not an easier way that I'm missing out? (That doesn't use P/Invoke!)

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  • C++: Calculate probability percentage during each iteration

    - by Mur Quirk
    Can't seem to get this to work. The idea is to calculate the percentage of heads and tails after each count, accumulating after each iteration. Except I keep getting nan% for my calculations. Anybody see what I'm doing wrong? void flipCoin(time_t seconds, int flipCount){ vector<int> flips; float headCount = 0; float tailCount = 0; double headProbability = double((headCount/(headCount + tailCount))*100); double tailProbability = double((tailCount/(headCount + tailCount))*100); for (int i=0; i < flipCount; i++) { int flip = rand() % (HEADS - TAILS + 1) + TAILS; flips.push_back(flip); if (flips[i] == 1) { tailCount++; cout << "Tail Percent: " << tailProbability << "%" << endl; }else{ headCount++; cout << "Head Percent: " << headProbability << "%" << endl; } } }

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  • ANDROID SAX Parser issue

    - by Chris Watson
    Since I am new to java programming, I need a bit of help with this. I stuck on this one issue and can't continue until I get this to work. I am trying to make a string from that includes a preference int. I saved the data and can display the int (just sample code): SharedPreferences prefs=PreferenceManager .getDefaultSharedPreferences(this); list.setText(prefs.getString("list", "22")); now, I have a xml parser that is pulling a url correctly as a static string: public static String feedUrl = String.format("http://www.freshpointmarketing.com/iphone/objects/XML/AND.php?ID=%d", 22); Works great... now my issue...... I need to have the preference "int" become the variable in the string, thus making it not static. static SharedPreferences prefs=PreferenceManager.getDefaultSharedPreferences(this); static int myVariable = prefs.getInt("list1", 22); public static String feedUrl = String.format("http://www.freshpointmarketing.com/iphone/objects/XML/AND.php?ID=%d", myVariable); If I take out all static references, I get an error on this: private void loadFeed(ParserType type){ try{ FeedParser parser = FeedParserFactory.getParser(type); long start = System.currentTimeMillis(); messages = parser.parse(); long duration = System.currentTimeMillis() - start; Log.i("AndroidNews", "Parser duration=" + duration); String xml = writeXml(); Log.i("AndroidNews", xml); List<String> titles = new ArrayList<String>(messages.size()); for (Message msg : messages){ titles.add(msg.getTitle()); } ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.row,titles); this.setListAdapter(adapter); } catch (Throwable t){ Log.e("AndroidNews",t.getMessage(),t); } } thanks

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  • Placing and removing element on array trough object

    - by Chris
    Hello, Lets assume i have 2 methods 1 that places a element on the array and one that removes it. const int Max = 10; int[] table= new int[Max]; I would like to call it up like this: s1.Place(5); // 5 0 0 0 0 0 0 0 0 0 0 s1.Place(9); // 5 9 0 0 0 0 0 0 0 0 0 s1.Remove(9); // 5 0 0 0 0 0 0 0 0 0 0 I would only like to use : using system for this. The result i get right now when i run the program is s1 = "nameofprogram" "name of class object" Normally i should get 0 0 0 0 0 0 0 0 0 0 to begin with. Any ideas how i can exactly add or remove those elements on the array? public void Place(int g) { if (top == Max) { throw new Exception("Stack overflow..."); } else { table[top] = g; top++; } .... Best Regards.

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  • const pod and std::vector

    - by Baz
    To get this code to compile: std::vector<Foo> factory() { std::vector<Foo> data; return data; } I have to define my POD like this: struct Foo { const int i; const int j; Foo(const int _i, const int _j): i(_i), j(_j) {} Foo(Foo& foo): i(foo.i), j(foo.j){} Foo operator=(Foo& foo) { Foo f(foo.i, foo.j); return f; } }; Is this the correct approach for defining a pod where I'm not interested in changing the pod members after creation? Why am I forced to define a copy constructor and overload the assignment operator? Is this compatible for different platform implementations of std::vector? Is it wrong in your opinion to have const PODS like this? Should I just leave them as non-const?

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  • sockaddr_in causing segfault?

    - by Curlystraw
    Working on creating a server/client system in C right now, and I'm having a little trouble with the client part. From what I've seen, I need to use sockaddr_in so I can connect to the server. However, I've been getting a segfault every time. I believe that sockaddr_in has something to do with it, as comment it and it's references later in the program fixes the segfault. code: #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <unistd.h> #include <netinet/in.h> int main(int argc, char** argv) { int Csock; int con; char *data = 0; char buf[101] = ""; struct sockaddr_in addr; Csock = socket(AF_INET, SOCK_STREAM, 0); addr.sin_family = AF_INET; addr.sin_port = htons(3435); con = connect(Csock, (struct sockaddr*) &addr, sizeof(&addr)); write(con, "Text", sizeof("Text")); *data = read(con, buf, 100); puts(data); return 0; } sadly, I am rather new to C, so that's as much as I can figure... can anyone tell me a way to go about eliminating the segfault? Thanks!

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  • Bizarre static_cast trick?

    - by Rob
    While perusing the Qt source code I came across this gem: template <class T> inline T qgraphicsitem_cast(const QGraphicsItem *item) { return int(static_cast<T>(0)->Type) == int(QGraphicsItem::Type) || (item && int(static_cast<T>(0)->Type) == item->type()) ? static_cast<T>(item) : 0; } Notice the static_cast<T>(0)->Type? I've been using C++ for many years but have never seen 0 being used in a static_cast before. What is this code doing and is it safe? Background: If you derive from QGraphicsItem you are meant to declare an unique enum value called Type that and implement a virtual function called type that returns it, e.g.: class Item : public QGraphicsItem { public: enum { Type = MAGIC_NUMBER }; int type() const { return Type; } ... }; You can then do this: QGraphicsItem* item = new Item; ... Item* derivedItem = qgraphicsitem_cast<Item*>(item); This will probably help explain what that static_cast is trying to do.

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  • How can a B-tree node be represented?

    - by chronodekar
    We're learning B-trees in class and have been asked to implement them in code. The teacher has left choice of programming language to us and I want to try and do it in C#. My problem is that the following structure is illegal in C#, unsafe struct BtreeNode { int key_num; // The number of keys in a node int[] key; // Array of keys bool leaf; // Is it a leaf node or not? BtreeNode*[] c; // Pointers to next nodes } Specifically, one is not allowed to create a pointer to point to the structure itself. Is there some work-around or alternate approach I could use? I'm fairly certain that there MUST be a way to do this within the managed code, but I can't figure it out. EDIT: Eric's answer pointed me in the right direction. Here's what I ended up using, class BtreeNode { public List<BtreeNode> children; // The child nodes public static int MinDeg; // The Minimum Degree of the tree public bool IsLeaf { get; set; } // Is the current node a leaf or not? public List<int> key; // The list of keys ... }

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  • Running Boggle Solver takes over an hour to run. What is wrong with my code?

    - by user1872912
    So I am running a Boggle Solver in java on the NetBeans IDE. When I run it, i have to quit after 10 minutes or so because it will end up taking about 2 hour to run completely. Is there something wrong with my code or a way that will make is substantially faster? public void findWords(String word, int iLoc, int jLoc, ArrayList<JLabel> labelsUsed){ if(iLoc < 0 || iLoc >= 4 || jLoc < 0 || jLoc >= 4){ return; } if(labelsUsed.contains(jLabels[iLoc][jLoc])){ return; } word += jLabels[iLoc][jLoc].getText(); labelsUsed.add(jLabels[iLoc][jLoc]); if(word.length() >= 3 && wordsPossible.contains(word)){ wordsMade.add(word); } findWords(word, iLoc-1, jLoc, labelsUsed); findWords(word, iLoc+1, jLoc, labelsUsed); findWords(word, iLoc, jLoc-1, labelsUsed); findWords(word, iLoc, jLoc+1, labelsUsed); findWords(word, iLoc-1, jLoc+1, labelsUsed); findWords(word, iLoc-1, jLoc-1, labelsUsed); findWords(word, iLoc+1, jLoc-1, labelsUsed); findWords(word, iLoc+1, jLoc+1, labelsUsed); labelsUsed.remove(jLabels[iLoc][jLoc]); } here is where I call this method from: public void findWords(){ ArrayList <JLabel> labelsUsed = new ArrayList<JLabel>(); for(int i=0; i<jLabels.length; i++){ for(int j=0; j<jLabels[i].length; j++){ findWords(jLabels[i][j].getText(), i, j, labelsUsed); //System.out.println("Done"); } } } edit: BTW I am using a GUI and the letters on the board are displayed by using a JLabel.

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  • expected identifier or '(' before '{' token in Flex

    - by user1829177
    I am trying to use Flex to parse 'C' source code. Unfortunately I am getting the error "expected identifier or '(' before '{' token" on lines 1,12,13,14... . Any ideas why? %{ %} digit [0-9] letter [a-zA-Z] number (digit)+ id (letter|_)(letter|digit|_)* integer (int) character (char) comma [,] %% {integer} {return INT;} {character} {return CHAR;} {number} {return NUM;} {id} {return IDENTIFIER;} {comma} {return ',';} [-+*/] {return *yytext;} . {} %% main() { yylex(); } The corresponding flex file is as shown below: %{ #include <ctype.h> #include <stdio.h> #include "myhead.h" #include "mini.l" #define YYSTYPE double # undef fprintf %} %token INT %token CHAR %token IDENTIFIER %token NUM %token ',' %left '+' '-' %left '*' '/' %right UMINUS %% lines:lines expr '\n' {printf("%g\n",$2);} |lines '\n' |D | ; expr :expr '*' expr {$$=$1*$3;} |expr '/' expr {$$=$1/$3;} |expr '+' expr {$$=$1+$3;} |expr '-' expr {$$=$1+$3;} |'(' expr ')' {$$=$2;} |'-' expr %prec UMINUS {$$=-$2;} |IDENTIFIER {} |NUM {} ; T :INT {} |CHAR {} ; L :L ',' IDENTIFIER {} |IDENTIFIER {} ; D :T L {printf("T is %g, L is %g",$1,$2);} ; %% /*void yyerror (char *s) { fprintf (stderr, "%s\n", s); } */ I am compiling the generated code using the command: gcc my_file.c -ly

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  • Generic delegate instances

    - by Luc C
    I wonder if C# (or the underlying .NET framework) supports some kind of "generic delegate instances": that is a delegate instance that still has an unresolved type parameter, to be resolved at the time the delegate is invoked (not at the time the delegate is created). I suspect this isn't possible, but I'm asking it anyway... Here is an example of what I'd like to do, with some "???" inserted in places where the C# syntax seems to be unavailable for what I want. (Obviously this code doesn't compile) class Foo { public T Factory<T>(string name) { // implementation omitted } } class Test { public void TestMethod() { Foo foo = new Foo(); ??? magic = foo.Factory; // No type argument given here yet to Factory! // What would the '???' be here (other than 'var' :) )? string aString = magic<string>("name 1"); // type provided on call int anInt = magic<int>("name 2"); // another type provided on another call // Note the underlying calls work perfectly fine, these work, but i'd like to expose // the generic method as a delegate. string aString2 = foo.Factory<string>("name 1"); int anInt2 = foo.Factory<int>("name 2"); } } Is there a way to actually do something like this in C#? If not, is that a limitation in the language, or is it in the .NET framework?

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  • Getting jsonString via Jquery coming up empty

    - by NoobCoder
    I'm using asp mvc and I'm getting data in one part of my program like this public List<IncidentPerAreaCount> getIncident() { int RondeboschCounter = 0; int ClaremontCounter = 0; int AthloneCounter = 0; List<IncidentPerAreaCount> IncidentAreaCount = new List<IncidentPerAreaCount>(); IncidentPerAreaCount Rondebosch = new IncidentPerAreaCount(); IncidentPerAreaCount Claremont = new IncidentPerAreaCount(); IncidentPerAreaCount Athlone = new IncidentPerAreaCount(); List<Report> Reports = GetReports(); for (int i = 0; i < Reports.Count(); i++) { if (Reports.AsEnumerable().ElementAt(i).Area == "Rondebosch") { RondeboschCounter++; } else if (Reports.AsEnumerable().ElementAt(i).Area == "Claremont") { ClaremontCounter++; } else if (Reports.AsEnumerable().ElementAt(i).Area == "Athlone") { AthloneCounter++; } } Rondebosch.AreaName = "Rondebosch"; Rondebosch.NumberOfIncidents = RondeboschCounter; Claremont.AreaName = "Claremont"; Claremont.NumberOfIncidents = ClaremontCounter; Athlone.AreaName = "Athlone"; Athlone.NumberOfIncidents = AthloneCounter; IncidentAreaCount.Add(Rondebosch); IncidentAreaCount.Add(Claremont); IncidentAreaCount.Add(Athlone); return IncidentAreaCount; } Then I'm trying to get this string via Jquery var Reports = []; $.ajax({ url: "Home/getIncident", async: false, dataType: 'json', success: function (json) { Reports = json.whatever; } }); alert(Reports); However the alert function keeps coming up empty (ie empty textbox) instead of having a json formatted string with data. Please help...

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  • Using new (this) to reuse constructors

    - by Brandon Bodnar
    This came up recently in a class for which I am a teaching assistant. We were teaching the students how to do copy constructors in c++, and the students who were originally taught java asked if you can call one constructor from another. I know the answer to this is no, as they are using the pedantic flag for their code in class, and the old standards do not have support for this. I found on Stackoverflow and other sites a suggestion to fake this using new (this) such as follows class MyClass { private: int * storedValue; public: MyClass(int initialValue = 0) { storedValue = new int(initialValue); } ~ MyClass() { delete storedValue; } MyClass(const MyClass &b) { new (this) MyClass(*(b.storedValue)); } int value() { return *storedValue; } }; This is really simple code, and obviously does not save any code by reusing the constructor, but it is just for example. My question is if this is even standard compliant, and if there are any edge cases that should be considered that would prevent this from being sound code?

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  • Equvalent c++0x program withought using boost threads..

    - by Eternal Learner
    I have the below simple program using boost threads, what would be the changes needed to do the same in c++0X #include<iostream> #include<boost/thread/thread.hpp> boost::mutex mutex; struct count { count(int i): id(i){} void operator()() { boost::mutex::scoped_lock lk(mutex); for(int i = 0 ; i < 10000 ; i++) { std::cout<<"Thread "<<id<<"has been called "<<i<<" Times"<<std::endl; } } private: int id; }; int main() { boost::thread thr1(count(1)); boost::thread thr2(count(2)); boost::thread thr3(count(3)); thr1.join(); thr2.join(); thr3.join(); return 0; }

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  • How to get the parameter names of an object's constructors (reflection)?

    - by Tom
    Say I somehow got an object reference from an other class: Object myObj = anObject; Now I can get the class of this object: Class objClass = myObj.getClass(); Now, I can get all constructors of this class: Constructor[] constructors = objClass.getConstructors(); Now, I can loop every constructor: if (constructors.length > 0) { for (int i = 0; i < constructors.length; i++) { System.out.println(constructors[i]); } } This is already giving me a good summary of the constructor, for example a constructor public Test(String paramName) is shown as public Test(java.lang.String) Instead of giving me the class type however, I want to get the name of the parameter.. in this case "paramName". How would I do that? I tried the following without success: if (constructors.length > 0) { for (int iCon = 0; iCon < constructors.length; iCon++) { Class[] params = constructors[iCon].getParameterTypes(); if (params.length > 0) { for (int iPar = 0; iPar < params.length; iPar++) { Field fields[] = params[iPar].getDeclaredFields(); for (int iFields = 0; iFields < fields.length; iFields++) { String fieldName = fields[i].getName(); System.out.println(fieldName); } } } } } Unfortunately, this is not giving me the expected result. Could anyone tell me how I should do this or what I am doing wrong? Thanks!

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  • C++: Conceptual problem in designing an intepreter

    - by sub
    I'm programming an interpreter for an experimental programming language (educational, fun,...) So far, everything went well (Tokenizer & Parser), but I'm getting a huge problem with some of the data structures in the part that actually runs the tokenized and parsed code. My programming language basically has only two types, int and string, and they are represented as C++ strings (std class) and ints Here is a short version of the data structure that I use to pass values around: enum DataType { Null, Int, String } class Symbol { public: string identifier; DataType type; string stringValue; int intValue; } I can't use union because string doesn't allow me to. This structure above is beginning to give me a headache. I have to scatter code like this everywhere in order to make it work, it is beginning to grow unmaintainable: if( mySymbol.type == Int ) { mySymbol.intValue = 1234; } else { mySymbol.stringValue = "abcde"; } I use the Symbol data structure for variables, return values for functions and general representation of values in the programming language. Is there any better way to solve this? I hope so!

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  • Data mixing SQL Server

    - by Pythonizo
    I have three tables and a range of two dates: Services ServicesClients ServicesClientsDone @StartDate @EndDate Services: ID | Name 1 | Supervisor 2 | Monitor 3 | Manufacturer ServicesClients: IDServiceClient | IDClient | IDService 1 | 1 | 1 2 | 1 | 2 3 | 2 | 2 4 | 2 | 3 ServicesClientsDone: IDServiceClient | Period 1 | 201208 3 | 201210 Period = YYYYMM I need to insert into ServicesClientsDone the months range from @StartDate up @EndDate. I have also a temporary table (#Periods) with the following list: Period 201208 201209 201210 The query I need is to give me back the following list: IDServiceClient | Period 1 | 201209 1 | 201210 2 | 201208 2 | 201209 2 | 201210 3 | 201208 3 | 201209 4 | 201208 4 | 201209 4 | 201210 Which are client services but the ranks of the temporary table, not those who are already inserted This is what i have: Table periods: DECLARE @i int DECLARE @mm int DECLARE @yyyy int, DECLARE @StartDate datetime DECLARE @EndDate datetime set @EndDate = (SELECT GETDATE()) set @StartDate = (SELECT DATEADD(MONTH, -3,GETDATE())) CREATE TABLE #Periods (Period int) set @i = 0 WHILE @i <= DATEDIFF(MONTH, @StartDate , @EndDate ) BEGIN SET @mm= DATEPART(MONTH, DATEADD(MONTH, @i, @FechaInicio)) SET @yyyy= DATEPART(YEAR, DATEADD(MONTH, @i, @FechaInicio)) INSERT INTO #Periods (Period) VALUES (CAST(@yyyy as varchar(4)) + RIGHT('00'+CONVERT(varchar(6), @mm), 2)) SET @i = @i + 1; END Relation between ServicesClients and Services: SELECT s.Name, sc.IDClient FROM Services JOIN ServicesClients AS sc ON sc.IDService = s.ID Services already done and when: SELECT s.Name, scd.Period FROM Services JOIN ServicesClients AS sc ON sc.IDService = s.ID JOIN ServicesClientsDone AS scd ON scd.IDServiceClient = sc.IDServiceClient

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  • dividing two array elements

    - by pradeep
    main() { int prime_array[2339],prime1_count=0,mul1_count=0; int i, prime, lim_up, lim_low, n,j=0; int mul,count=0; int mul_count[65026]={0},number[7096]; printf("\n ENTER THE LOWER LIMIT…: "); scanf("%d", &lim_low); printf("\n ENTER THE UPPER LIMIT…: "); scanf("%d", &lim_up); for(n=lim_low+1; n<lim_up; n++) { prime = 1; for(i=2; i<n; i++) if(n%i == 0) { prime = 0; break; } if(prime) { prime_array[j]=n; j++; } } for(i=1;i<=255;i++) { for(j=1;j<=255;j++) { mul = j*i; mul_count[mul]++; } } for(i=1;i<=65025;i++) if( mul_count[i]!=2 && mul_count[i]!=0 ) { number[count]=i; count++; } for(prime1_count=0;prime1_count<2339;prime1_count++) { printf("\nprime number used is:%d",prime_array[prime1_count]); for(mul1_count=0;mul1_count<7096;mul1_count++) { printf("\n%d\t",number[mul1_count] % prime_array[prime1_count]); } } } I want to find the modulus of (number[mul1_count] % prime_array[prime1_count] ), but the output which I get is wrong. What is the mistake here. The prime number should be in the range 40000 to 65025. What changes should i make here?

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  • Trying to instantiate a class member in C++ with a variable name

    - by MarcZero
    Hello. I am writing a program for class that is asking us to create a class of "book". We are then supposed to create new instantiations of that class upon demand from the user. I am new to C++ so I am attempting to code this out but am running into a problem. The main problem is how do I instantiate a class with a variable if I don't know how many I will have to do ahead of time. The user could ask to add 1 book or 1000. I am looking at this basic code: This is the simple code I started with. I wanted to have an index int keep a number and have the book class I create be called by that int (0, 1, 2, etc...) So I attempted to convert the incoming index int into a string, but I'm kind of stuck from here. void addBook(int index){ string bookName; std::stringstream ss; ss << index; book bookName; cout << "Enter the Books Title: "; cin >> bookName.title; } But obviously this doesn't work as "bookName" is a string to the computer and not the class member I tried to create. All of the tutorials I have seen online and in my text show the classes being instantiated with names in the code, but I just don't know how to make it variable so I can create any amount of "books" that the user might want. Any insight on this would be appreciated. Thank you for your time.

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