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  • Is it possible to create a throttle function that can take in as parameters another function (that also has parameters), and the time delay

    - by Stan Quinn
    So I've already written a function that works (based on underscores throttle) for functions that don't take in a parameter, but I'd like to make it generic enough to pass in a function with a variable number of parameters. Here's what I have: (function () { var lastTime = new Date().getTime(); function foo() { var newTime = new Date().getTime(); var gap = newTime - lastTime; // Travels up scope chain to use parents lastTime. Function has access to variables declared in the same scope console.log('foo called, gap:' + gap); lastTime = newTime; // Updates lastTime //console.log(x); //x++; } var throttle = function(func, wait) { var result; var timeout = null; // flag updated through closure var previous = 0; // time last run updated through closure return function() { //func, wait, timeout, previous available through scope var now = new Date().getTime(); var remaining = wait - (now - previous); if (remaining <= 0) { clearTimeout(timeout); timeout = null; previous = now; result = func.apply(this, arguments); //func is available through closure } return result; }; }; document.addEventListener("scroll", throttle(foo, 1000)); //document.addEventListener("scroll", throttle(foo(5), 2000)); }()); But I'd like to modify foo to foo(x) and get this to work (function () { var lastTime = new Date().getTime(); function foo(x) { var newTime = new Date().getTime(); var gap = newTime - lastTime; // Travels up scope chain to use parents lastTime. Function has access to variables declared in the same scope console.log('foo called, gap:' + gap); lastTime = newTime; // Updates lastTime console.log(x); x++; } var throttle = function(func, wait) { var result; var timeout = null; // flag updated through closure var previous = 0; // time last run updated through closure return function() { //func, wait, timeout, previous available through scope var now = new Date().getTime(); var remaining = wait - (now - previous); if (remaining <= 0) { clearTimeout(timeout); timeout = null; previous = now; result = func.apply(this, arguments); //func is available through closure } return result; }; }; document.addEventListener("scroll", throttle(foo(5), 2000)); }());

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  • What's the fastest lookup algorithm for a key, pair data structure (i.e, a map)?

    - by truncheon
    In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 – 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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  • How can I obtain the IP address of my server program?

    - by Dr Dork
    Hello! This question is related to another question I just posted. I'm prepping for a simple work project and am trying to familiarize myself with the basics of socket programming in a Unix dev environment. At this point, I have some basic server side code and client side code setup to communicate. Currently, my client code successfully connects to the server code and the server code sends it a test message, then both quit out. Perfect! That's exactly what I wanted to accomplish. Now I'm playing around with the functions used to obtain info about the two environments (server and client). I'd like to obtain my server program's IP address. Here's the code I currently have to do this, but it's not working... int sockfd; unsigned int len; socklen_t sin_size; char msg[]="test message"; char buf[MAXLEN]; int st, rv; struct addrinfo hints, *serverinfo, *p; struct sockaddr_storage client; char s[INET6_ADDRSTRLEN]; char ip[INET6_ADDRSTRLEN]; //zero struct memset(&hints,0,sizeof(hints)); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; //get the server info if((rv = getaddrinfo(NULL, SERVERPORT, &hints, &serverinfo ) != 0)){ perror("getaddrinfo"); exit(-1); } // loop through all the results and bind to the first we can for( p = serverinfo; p != NULL; p = p->ai_next) { //Setup the socket if( (sockfd = socket( p->ai_family, p->ai_socktype, p->ai_protocol )) == -1 ) { perror("socket"); continue; } //Associate a socket id with an address to which other processes can connect if(bind(sockfd, p->ai_addr, p->ai_addrlen) == -1){ close(sockfd); perror("bind"); continue; } break; } if( p == NULL ){ perror("Fail to bind"); } inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr), s, sizeof(s)); printf("Server has TCP Port %s and IP Address %s\n", SERVERPORT, s); and the output for the IP is always empty... server has TCP Port 21412 and IP Address :: any ideas for what I'm missing? thanks in advance for your help! this stuff is really complicated at first.

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  • Mixing C and C++, raw pointers and (boost) shared pointers

    - by oompahloompah
    I am working in C++ with some legacy C code. I have a data structure that (during initialisation), makes a copy of the structure pointed to a ptr passed to its initialisation pointer. Here is a simplification of what I am trying to do - hopefully, no important detail has been lost in the "simplification": /* C code */ typedef struct MyData { double * elems; unsigned int len; }; int NEW_mydata(MyData* data, unsigned int len) { // no error checking data->elems = (double *)calloc(len, sizeof(double)); return 0; } typedef struct Foo { MyData data data_; }; void InitFoo(Foo * foo, const MyData * the_data) { //alloc mem etc ... then assign the STRUCTURE foo.data_ = *thedata ; } C++ code ------------- typedef boost::shared_ptr<MyData> MyDataPtr; typedef std::map<std::string, MyDataPtr> Datamap; class FooWrapper { public: FooWrapper(const std::string& key) { MyDataPtr mdp = dmap[key]; InitFoo(&m_foo, const_cast<MyData*>((*mdp.get()))); } ~FooWrapper(); double get_element(unsigned int index ) const { return m_foo.elems[index]; } private: // non copyable, non-assignable FooWrapper(const FooWrapper&); FooWrapper& operator= (const FooWrapper&); Foo m_foo; }; int main(int argc, char *argv[]) { MyData data1, data2; Datamap dmap; NEW_mydata(&data1, 10); data1->elems[0] = static_cast<double>(22/7); NEW_mydata(&data2, 42); data2->elems[0] = static_cast<double>(13/21); boost::shared_ptr d1(&data1), d2(&data2); dmap["data1"] = d1; dmap["data2"] = d2; FooWrapper fw("data1"); //expect 22/7, get something else (random number?) double ret fw.get_element(0); } Essentially, what I want to know is this: Is there any reason why the data retrieved from the map is different from the one stored in the map?

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  • Code to generate random numbers in C++

    - by user1678927
    Basically I have to write a program to generate random numbers to simulate the rolling of a pair of dice. This program should be constructed in multiple files. The main function should be in one file, the other functions should be in a second source file, and their prototypes should be in a header file. First I write a short function that returns a random value between 1 and 6 to simulate the rolling of a single 6-sided die.Second, i write a function that pretends to roll a pair of dice by calling this function twice. My program starts by asking the user how many rolls should be made. Then I write a function to simulate rolling the dice this many times, keeping a count of exactly how many times the values 2,3,4,5,6,7,8,9,10,11,12(each number is the sum of a pair of dice) occur in an array. Later I write a function to display a small bar chart using these counts that ideally would look something like below for a sample of 144 rolls, where the number of asterisks printed corresponds to the count: 2 3 4 5 6 7 8 9 10 11 12 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Next, to see how well the random number generator is doing, I write a function to compute the average value rolled. Compare this to the ideal average of 7. Also, print out a small table showing the counts of each roll made by the program, the ideal count based on the frequencies above given the total number of rolls, and the difference between these values in separate columns. This is my incomplete code so far: "Compiler visual studio 2010" int rolling(){ //Function that returns a random value between 1 and 6 rand(unsigned(time(NULL))); int dice = 1 + (rand() %6); return dice; } int roll_dice(int num1,int num2){ //it calls 'rolling function' twice int result1,result2; num1 = rolling(); num2 = rolling(); result1 = num1; result2 = num2; return result1,result2; } int main(void){ int times,i,sum,n1,n2; int c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11;//counters for each sum printf("Please enter how many times you want to roll the dice.\n") scanf_s("%i",&times); I pretend to use counters to count each sum and store the number(the count) in an array. I know i need a loop (for) and some conditional statements (if) but m main problem is to get the values from roll_dice and store them in n1 and n2 so then i can sum them up and store the sum in 'sum'.

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  • C problem, left of '->' must point to class/struct/union/generic type ??

    - by Patrick
    Hello! Trying to understand why this doesn't work. I keep getting the following errors: left of '-nextNode' must point to class/struct/union/generic type (Also all the lines with a - in the function new_math_struct) Header file #ifndef MSTRUCT_H #define MSTRUCT_H #define PLUS 0 #define MINUS 1 #define DIVIDE 2 #define MULTIPLY 3 #define NUMBER 4 typedef struct math_struct { int type_of_value; int value; int sum; int is_used; struct math_struct* nextNode; } ; typedef struct math_struct* math_struct_ptr; #endif C file int get_input(math_struct_ptr* startNode) { /* character, input by the user */ char input_ch; char* input_ptr; math_struct_ptr* ptr; math_struct_ptr* previousNode; input_ptr = &input_ch; previousNode = startNode; /* as long as input is not ok */ while (1) { input_ch = get_input_character(); if (input_ch == ',') // Carrage return return 1; else if (input_ch == '.') // Illegal character return 0; if (input_ch == '+') ptr = new_math_struct(PLUS, 0); else if (input_ch == '-') ptr = new_math_struct(MINUS, 0); else if (input_ch == '/') ptr = new_math_struct(DIVIDE, 0); else if (input_ch == '*') ptr = new_math_struct(MULTIPLY, 0); else ptr = new_math_struct(NUMBER, atoi(input_ptr)); if (startNode == NULL) { startNode = previousNode = ptr; } else { previousNode->nextNode = ptr; previousNode = ptr; } } return 0; } math_struct_ptr* new_math_struct(int symbol, int value) { math_struct_ptr* ptr; ptr = (math_struct_ptr*)malloc(sizeof(math_struct_ptr)); ptr->type_of_value = symbol; ptr->value = value; ptr->sum = 0; ptr->is_used = 0; return ptr; } char get_input_character() { /* character, input by the user */ char input_ch; /* get the character */ scanf("%c", &input_ch); if (input_ch == '+' || input_ch == '-' || input_ch == '*' || input_ch == '/' || input_ch == ')') return input_ch; // A special character else if (input_ch == '\n') return ','; // A carrage return else if (input_ch < '0' || input_ch > '9') return '.'; // Not a number else return input_ch; // Number } The header for the C file just contains a reference to the struct header and the definitions of the functions. Language C.

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  • How can I remove rows with unique values? As in only keeping rows with duplicate values?

    - by user1456405
    Here's the conundrum, I'm a complete and utter noob when it comes to programming. I understand the basics, but am still learning javascript. I have a spreadsheet of surveys, in which I need to see how particular users have varied over time. As such, I need to disregard all rows with unique values in a particular column. The data looks like this: Response Date Response_ID Account_ID Q.1 10/20/2011 12:03:43 PM 23655956 1168161 8 10/20/2011 03:52:57 PM 23660161 1168152 0 10/21/2011 10:55:54 AM 23672903 1166121 7 10/23/2011 04:28:16 PM 23694471 1144756 9 10/25/2011 06:30:52 AM 23732674 1167449 7 10/25/2011 07:52:28 AM 23734597 1087618 5 I've found a way to do so in VBA, which sucks as I have to use excel, per below: Sub Del_Unique() Application.ScreenUpdating = False Columns("B:B").Insert Shift:=xlToRight Columns("A:A").Copy Destination:=Columns("B:B") i = Application.CountIf(Range("A:A"), "<>") + 50 If i > 65536 Then i = 65536 Do If Application.CountIf(Range("B:B"), Range("A" & i)) = 1 Then Rows(i).Delete End If i = i - 1 Loop Until i = 0 Columns("B:B").Delete Application.ScreenUpdating = True End Sub But that requires mucking about. I'd really like to do it in Google Spreadsheets with a script that won't have to be changed. Closest I can get is retrieving all duplicate user ids from the range, but can't associate that with the row. That code follows: function findDuplicatesInSelection() { var activeRange = SpreadsheetApp.getActiveRange(); var values = activeRange.getValues(); // values that appear at least once var once = {}; // values that appear at least twice var twice = {}; // values that appear at least twice, stored in a pretty fashion! var final = []; for (var i = 0; i < values.length; i++) { var inner = values[i]; for (var j = 0; j < inner.length; j++) { var cell = inner[j]; if (cell == "") continue; if (once.hasOwnProperty(cell)) { if (!twice.hasOwnProperty(cell)) { final.push(cell); } twice[cell] = 1; } else { once[cell] = 1; } } } if (final.length == 0) { Browser.msgBox("No duplicates found"); } else { Browser.msgBox("Duplicates are: " + final); } } Anyhow, sorry if this is the wrong place or format, but half of what I've found so far has been from stack, I thought it was a good place to start. Thanks!

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  • priority_queue with dynamic priorities

    - by Layne
    Hey, I have a server application which accepts incomming queries and executes them. If there are too many queries they should be queued and if some of the other queries got executed the queued queries should be executed as well. Since I want to pass queries with different priorities I think using a priority_queue would be the best choice. e.g. The amout of the axcepting queries (a) hit the limt and new queries will be stored in the queue. All queries have a priority of 1 (lowest) if some of the queries from (a) get executed the programm will pick the query with the highest priority out of the queue and execute it. Still no problem. Now someone is sending a query with a priority of 5 which gets added to the queue. Since this is the query with the highest priority the application will execute this query as soon as the running queries no longer hit the limit. There might be the worst case that 500 queries with a priority of 1 are queued but wont be executed since someone is always sending queries with a priority of 5 hence these 500 queries will be queued for a looooong time. In order to prevent that I want to increase the prioritiy of all queries which have a lower priority than the query with the higher priority, in this example which have a priority lower than 5. So if the query with a priority of 5 gets pulled out of the queue all other queries with a priority < 5 should be increased by 0.2. This way queries with a low priority wont be queued for ever even if there might be 100 queries with a higher priority. I really hope can help me to solve the problem with the priorities: Since my queries consist of an object I thought something like this might work: class Query { public: Query( std::string p_stQuery ) : stQuery( p_stQuery ) {}; std::string getQuery() const {return stQuery;}; void increasePriority( const float fIncrease ) {fPriority += fIncrease;}; friend bool operator < ( const Query& PriorityFirst, const Query& PriorityNext ) { if( PriorityFirst.fPriority < PriorityNext.fPriority ) { if( PriorityFirst.fStartPriority < PriorityNext.fStartPriority ) { Query qTemp = PriorityFirst; qTemp.increasePriority( INCREASE_RATE ); } return true; } else { return false; } }; private: static const float INCREASE_RATE = 0.2; float fPriority; // current priority float fStartPriority; // initialised priority std::string stQuery; };

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  • Convert Object Hierachey to Object Array

    - by Killercam
    All, I want to create an object array foo[], where the constructor for Foo is public Foo(string name, string discription){} I have a database object which has a structure (not incuding stored procedures, functions or views for simplicity) like public class Database { public string name { get; set; } public string filename { get; set; } public List<Table> tables { get; set; } public Database(string name, string filename) { this.name = name; this.filename = filename; } } protected internal class Table { public string name { get; set; } public List<Column> columns { get; set;} public Table(string name, List<Column> columns) { this.name = name; this.columns = columns; } } protected internal class Column { public string name { get; set; } public string type { get; set; } public Column(string name, string type, int maxLength, bool isNullable) { this.name = name; this.type = type; } } I would like to know the quickest way to add Column and Table information to the Foo[] object array? Clearly I can do List<Foo> fooList = new List<Foo>(); foreach (Table t in database.tables) { fooList.Add(new Foo(t.Name, "Some Description")); foreach (Column c in t.columns) fooList.Add(new Foo(c.Name, "Some Description")); } Foo[] fooArr = fooList.ToArray<Foo>(); But is there a quicker way? Clearly LINQ is likely to be slower for a query that does a simalar operation, but I care allot about speed here so any advice would be appreciated. Perhaps the use of a HashSet would be the way to go as there will not be duplicate entries... Thanks for your time.

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  • Icon placement relative to list items

    - by Ronedog
    When I show a hidden div that is stored inside an <li> tag the icons are pushing down to the bottom of the <li>. How can I prevent this? Here's the HTML: <ul> <li>Utah <ul> <li>Park City <ul> <li>Park Cat 1 <div><img class="portf_edit" /></div> <div><img class="portf_archive" /></div> <div><img class="portf_delete" /></div> </li> <li>Skiing <div><img class="portf_edit" /></div> <div><img class="portf_archive" /></div> <div><img class="portf_delete" /></div> </li> </ul> </li> </ul> </li> </ul> Here's the li css: li { list-style-type:none; vertical-align: top; list-style-image: none; left:0px; text-align:left; clear: both; } .portf_edit{ float:right; position: relative; right:50px; display:block; } .portf_archive{ float:right; position: relative; right:-5px; display:block; } .portf_delete{ float:right; position: relative; right: -60px; display:block; } Here's a screen shot prior to expanding which shows the icons how I want them to line up: Here's the screen shot prior to expanding which shows where the icons are being pushed to:

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  • What is the best approach in SQL to store multi-level descriptions?

    - by gime
    I need a new perspective on how to design a reliable and efficient SQL database to store multi-level arrays of data. This problem applies to many situations but I came up with this example: There are hundreds of products. Each product has an undefined number of parts. Each part is built from several elements. All products are described in the same way. All parts would require the same fields to describe them (let's say: price, weight, part name), all elements of all parts also have uniform design (for example: element code, manufacturer). Plain and simple. One element may be related to only part, and each part is related to one product only. I came up with idea of three tables: Products: -------------------------------------------- prod_id prod_name prod_price prod_desc 1 hoover 120 unused next Parts: ---------------------------------------------------- part_id part_name part_price part_weight prod_id 3 engine 10 20 1 and finally Elements: --------------------------------------- el_id el_code el_manufacturer part_id 1 BFG12 GE 3 Now, select a desired product, select all from PARTS where prod_id is the same, and then select all from ELEMENTS where part_id matches - after multiple queries you've got all data. I'm just not sure if this is the right approach. I've got also another idea, without ELEMENTS table. That would decrease queries but I'm a bit afraid it might be lame and bad practice. Instead of ELEMENTS table there are two more fields in the PARTS table, so it looks like this: part_id, part_name, part_price, part_weight, prod_id, part_el_code, part_el_manufacturer they would be text type, and for each part, information about elements would be stored as strings, this way: part_el_code | code_of_element1; code_of_element2; code_of_element3 part_el_manufacturer | manuf_of_element1; manuf_of_element2; manuf_of_element3 Then all we need is to explode() data from those fields, and we get arrays, easy to display. Of course this is not perfect and has some limitations, but is this idea ok? Or should I just go with the first idea? Or maybe there is a better approach to this problem? It's really hard to describe it in few words, and that means it's hard to search for answer. Also, understanding the principles of designing databases is not that easy as it seems.

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  • c++ program debugged well with Cygwin4 (under Netbeans 7.2) but not with MinGW (under QT 4.8.1)

    - by GoldenAxe
    I have a c++ program which take a map text file and output it to a graph data structure I have made, I am using QT as I needed cross-platform program and GUI as well as visual representation of the map. I have several maps in different sizes (8x8 to 4096x4096). I am using unordered_map with a vector as key and vertex as value, I'm sending hash(1) and equal functions which I wrote to the unordered_map in creation. Under QT I am debugging my program with QT 4.8.1 for desktop MinGW (QT SDK), the program works and debug well until I try the largest map of 4096x4096, then the program stuck with the following error: "the inferior stopped because it received a signal from operating system", when debugging, the program halt at the hash function which used inside the unordered_map and not as part of the insertion state, but at a getter(2). Under Netbeans IDE 7.2 and Cygwin4 all works fine (debug and run). some code info: typedef std::vector<double> coordinate; typedef std::unordered_map<coordinate const*, Vertex<Element>*, container_hash, container_equal> vertexsContainer; vertexsContainer *m_vertexes (1) hash function: struct container_hash { size_t operator()(coordinate const *cord) const { size_t sum = 0; std::ostringstream ss; for ( auto it = cord->begin() ; it != cord->end() ; ++it ) { ss << *it; } sum = std::hash<std::string>()(ss.str()); return sum; } }; (2) the getter: template <class Element> Vertex<Element> *Graph<Element>::getVertex(const coordinate &cord) { try { Vertex<Element> *v = m_vertexes->at(&cord); return v; } catch (std::exception& e) { return NULL; } } I was thinking maybe it was some memory issue at the beginning, so before I was thinking of trying Netbeans I checked it with QT on my friend pc with a 16GB RAM and got the same error. Thanks.

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  • I cannot get mlocManager.removeUpdates(mlocListener); to work

    - by Colin
    I have an app that uses the LocationManage functions which works well until the app is stopped or paused. The location listener function is still carrying on in the background. Relevant bits of code follow. When I click home or back the onstop() function is being triggered correctly. package uk.cr.anchor; import android.app.Activity; import android.content.Context; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; import android.media.MediaPlayer; import android.media.RingtoneManager; import android.net.Uri; import android.os.Bundle; import android.view.View; import android.widget.EditText; import android.widget.TableRow; import android.widget.Toast; import android.widget.ToggleButton; import android.content.SharedPreferences; import android.graphics.Color; public class main extends Activity { /** Called when the activity is first created. */ private LocationManager mlocManager; private LocationListener mlocListener; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); LocationManager mlocManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE); LocationListener mlocListener = new MyLocationListener(); mlocManager.requestLocationUpdates( LocationManager.GPS_PROVIDER, 0, 0, mlocListener); } @Override protected void onStop(){ stoplistening(); super.onStop(); } /* Class My Location Listener */ public class MyLocationListener implements LocationListener { @Override public void onLocationChanged(Location loc) { loc.getLatitude(); loc.getLongitude(); etc etc etc } private void stoplistening() { if (mlocManager != null) { Toast.makeText( getApplicationContext(), "kill", Toast.LENGTH_SHORT ).show(); mlocManager.removeUpdates(mlocListener); } else { Toast.makeText( getApplicationContext(), " not kill", Toast.LENGTH_SHORT ).show(); } } } I always get the "not kill" message. Can anyone help me!

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  • Indexing with pointer C/C++

    - by Leavenotrace
    Hey I'm trying to write a program to carry out newtons method and find the roots of the equation exp(-x)-(x^2)+3. It works in so far as finding the root, but I also want it to print out the root after each iteration but I can't get it to work, Could anyone point out my mistake I think its something to do with my indexing? Thanks a million :) #include <stdio.h> #include <math.h> #include <malloc.h> //Define Functions: double evalf(double x) { double answer=exp(-x)-(x*x)+3; return(answer); } double evalfprime(double x) { double answer=-exp(-x)-2*x; return(answer); } double *newton(double initialrt,double accuracy,double *data) { double root[102]; data=root; int maxit = 0; root[0] = initialrt; for (int i=1;i<102;i++) { *(data+i)=*(data+i-1)-evalf(*(data+i-1))/evalfprime(*(data+i-1)); if(fabs(*(data+i)-*(data+i-1))<accuracy) { maxit=i; break; } maxit=i; } if((maxit+1==102)&&(fabs(*(data+maxit)-*(data+maxit-1))>accuracy)) { printf("\nMax iteration reached, method terminated"); } else { printf("\nMethod successful"); printf("\nNumber of iterations: %d\nRoot Estimate: %lf\n",maxit+1,*(data+maxit)); } return(data); } int main() { double root,accuracy; double *data=(double*)malloc(sizeof(double)*102); printf("NEWTONS METHOD PROGRAMME:\nEquation: f(x)=exp(-x)-x^2+3=0\nMax No iterations=100\n\nEnter initial root estimate\n>> "); scanf("%lf",&root); _flushall(); printf("\nEnter accuracy required:\n>>"); scanf("%lf",&accuracy); *data= *newton(root,accuracy,data); printf("Iteration Root Error\n "); printf("%d %lf \n", 0,*(data)); for(int i=1;i<102;i++) { printf("%d %5.5lf %5.5lf\n", i,*(data+i),*(data+i)-*(data+i-1)); if(*(data+i*sizeof(double))-*(data+i*sizeof(double)-1)==0) { break; } } getchar(); getchar(); free(data); return(0); }

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  • makecontext segfault?

    - by cdietschrun
    I am working on a homework assignment that will be due in the next semester. It requires us to implement our own context switching/thread library using the ucontext API. The professor provides code that does it, but before a thread returns, he manually does some work and calls an ISR that finds another thread to use and swapcontexts to it or if none are left, exits. The point of the assignment is to use the uc_link field of the context so that when it hits a return it takes care of the work. I've created a function (type void/void args) that just does the work the functions did before (clean up and then calls ISR). The professor said he wanted this. So all that's left is to do a makecontext somewhere along the way on the context in the uc_link field so that it runs my thread, right? Well, when I do makecontext on seemingly any combination of ucontext_t's and function, I get a segfault and gdb provides no help.. I can skip the makecontext and my program exist 'normally' when it hits a return in the threads I created because (presumably) the uc_link field is not properly setup (which is what I'm trying to do). I also can't find anything on why makecontext would segfault. Can anyone help? stack2.ss_sp = (void *)(malloc(STACKSIZE)); if(stack2.ss_sp == NULL){ printf("thread failed to get stack space\n"); exit(8); } stack2.ss_size = STACKSIZE; stack2.ss_flags = 0; if(getcontext(&main_context) == -1){ perror("getcontext in t_init, rtn_env"); exit(5); } //main_context.uc_stack = t_state[i].mystk; main_context.uc_stack = stack2; main_context.uc_link = 0; makecontext(&main_context, (void (*)(void))thread_rtn, 0); I've also tried just thread_rtn, &thread_rtn and other things. thread_rtn is declared as void thread_rtn(void). later, in each thread. run_env is of type ucontext_t: ... t_state[i].run_env.uc_link = &main_context;

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  • C++ dynamic type construction and detection

    - by KneLL
    There was an interesting problem in C++, but it concerns more likely architecture. There are many (10, 20, 40, etc) classes that describe some characteristics (mix-in classes), for exmaple: struct Base { virtual ~Base() {} }; struct A : virtual public Base { int size; }; struct B : virtual public Base { float x, y; }; struct C : virtual public Base { bool some_bool_state; }; struct D : virtual public Base { string str; } // .... Primary module declares and exports a function (for simplicity just function declarations without classes): // .h file void operate(Base *pBase); // .cpp file void operate(Base *pBase) { // .... } Any other module can has a code like this: #include "mixins.h" #include "primary.h" class obj1_t : public A, public C, public D {}; class obj2_t : public B, public D {}; // ... void Pass() { obj1_t obj1; obj2_t obj2; operate(&obj1); operate(&obj2); } The question is how to know what the real type of given object in operate() without dynamic_cast and any type information in classes (constants, etc)? Function operate() is used with big array of objects in small time periods and dynamic_cast is too slow for it. And I don't want to include constants (enum obj_type { ... }) because this is not OOP-way. // module operate.cpp void some_operate(Base *pBase) { processA(pBase); processB(pBase); } void processA(A *pA) { } void processB(B *pB) { } I cannot directly pass a pBase to these functions. And it's impossible to have all possible combinations of classes, because I can add new classes just by including new .h files. As one of solutions that comed to mind, in editor application I can use a composite container: struct CompositeObject { vector<Base *pBase> parts; }; But editor does not need a time optimization and can use dynamic_cast for parts to determine the exact type. In operate() I cannot use this solution. So, is it possible to not use a dynamic_cast and type information to solve this problem? Or maybe I should use another architecture?

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  • JavaScript: Can I declare a variable by querying which function is called? (Newbie)

    - by belle3WA
    I'm working with an existing JavaScript-powered cart module that I am trying to modify. I do not know JS and for various reasons need to work with what is already in place. The text that appears for my quantity box is defined within an existing function: function writeitems() { var i; for (i=0; i<items.length; i++) { var item=items[i]; var placeholder=document.getElementById("itembuttons" + i); var s="<p>"; // options, if any if (item.options) { s=s+"<select id='options"+i+"'>"; var j; for (j=0; j<item.options.length; j++) { s=s+"<option value='"+item.options[j].name+"'>"+item.options[j].name+"</option>"; } s=s+"</select>&nbsp;&nbsp;&nbsp;"; } // add to cart s=s+method+"Quantity: <input id='quantity"+i+"' value='1' size='3'/> "; s=s+"<input type='submit' value='Add to Cart' onclick='addtocart("+i+"); return false;'/></p>"; } placeholder.innerHTML=s; } refreshcart(false); } I have two different types of quantity input boxes; one (donations) needs to be prefaced with a dollar sign, and one (items) should be blank. I've taken the existing additem function, copied it, and renamed it so that there are two identical functions, one for items and one for donations. The additem function is below: function additem(name,cost,quantityincrement) { if (!quantityincrement) quantityincrement=1; var index=items.length; items[index]=new Object; items[index].name=name; items[index].cost=cost; items[index].quantityincrement=quantityincrement; document.write("<span id='itembuttons" + index + "'></span>"); return index; } Is there a way to declare a global variable based on which function (additem or adddonation) is called so that I can add that into the writeitems function so display or hide the dollar sign as needed? Or is there a better solution? I can't use HTML in the body of the cart page because of the way it is currently coded, so I'm depending on the JS to take care of it. Any help for a newbie is welcome. Thanks!

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  • SSIS - user variable used in derived column transform is not available - in some cases

    - by soo
    Unfortunately I don't have a repro for my issue, but I thought I would try to describe it in case it sounds familiar to someone... I am using SSIS 2005, SP2. My package has a package-scope user variable - let's call it user_var first step in the control flow is an Execute SQL task which runs a stored procedure. All that SP does is insert a record in a SQL table (with an identity column) and then go back and get the max ID value. The Execute SQL task saves this output into user_var the control flow then has a Data Flow Task - it goes and gets some source data, has a derived column which sets a column called run_id to user_var - and saves the data to a SQL destination In most cases (this template is used for many packages, running every day) this all works great. All of the destination records created get set with a correct run_id. However, in some cases, there is a set of the destination data that does not get run_id equal to user_var, but instead gets a value of 0 (0 is the default value for user_var). I have 2 instances where this has happened, but I can't make it happen. In both cases, it was just less that 10,000 records that have run_id = 0. Since SSIS writes data out in 10,000 record blocks, this really makes me think that, for the first set of data written out, user_var was not yet set. Then, after that first block, for the rest of the data, run_id is set to a correct value. But control passed on to my data flow from the Execute SQL task - it would have seemed reasonable to me that it wouldn't go on until the SP has completed and user_var is set. Maybe it just runs the SP, but doesn't wait for it to complete? In both cases where this has happened there seemed to be a few packages hitting the table to get a new user_var at about the same time. And in both cases lots of data was written (40 million rows, 60 million rows) - my thinking is that that means the writes were happening for a while. Sorry to be both long-winded AND vague. A winning combination! Does this sound familiar to anyone? Thanks.

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  • Is this a good approach to dealing with tagging?

    - by Mel
    Can this code be optimized or re-factored? Is this an optimal approach to tagging? The following code is a callback in my posts model. It creates a record that associates a tag with a post in a QuestionsTags joiner table. When necessary, if a given tag does not already exist in the tags table, the function creates it, then uses its id to create the new record in the QuestionsTags table. The difficulty with this approach is the QuestionsTags table depends on data in the tags table which may or may not exist. The function assumes the following tables: tags(id, tagName), posts(tags) // Comma delimited list questionsTags(postId, tagId) The idea is to loop over a delimited list of tags submitted with a post and check to see if each tag already exists in the tags table If tag exists: Check to see if there's already a QuestionTag record for this post and this tag in the QuestionTags table. If yes, do nothing (the association already exists) If no, create a new QuestionTag record using the id of the existing tag and the postId If tag does not already exist: Create the new tag in the tags table Use its id to create a new QuestionsTags record Code /** * @hint Sets tags for a given question. **/ private function setTags() { // Loop over the comma and space delmited list of tags for (local.i = 1; local.i LTE ListLen(this.tags, ", "); local.i = (local.i + 1)) { // Check if the tag already exists in the database local.tag = model("tag").findOneByTagName(local.i); // If the tag exists, look for an existing association between the tag and the question in the QuestionTag table if (IsObject(local.tag)) { local.questionTag = model("questionTag").findOneByPostIdAndTagId(values="#this.postId#,#local.tag.id#"); // If no assciatione exists, create a new QuestionTag record using the tagId and the postId if (! IsObject(local.questionTag)) { local.newQuestionTag = model("questionTag").new(postId = this.id, tagId = local.tag.id); // Abort if the saving the new QuestionTag is unsuccesful if (! local.newQuestionTag.save()) { return false; } } } // If the tag does not exist create it else { local.newTag = model("tag").new(tagName = local.i, userId = this.ownerUserId); // Abort if the the new tag is not saved successfully if (! local.newTag.save()) { return false; } // Otherwise create a new association in the QuestionTags table using the id of the newly created tag and the postId local.newQuestionTag = model("questionTag").new(postId = this.id, tagId = local.newTag.id); // Abort if the new QuestionTag does not save correctly if (! local.newQuestionTag.save()) { return false; } } } } FYI: I'm using CFWheels in my application, which explains the ORM functions used.

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  • PHP-OOP extending two classes?

    - by user1292810
    I am very beginner to OOP and now I am trying to write some PHP class to connect with FTP server. class ftpConnect { private $server; private $user; private $password; private $connection_id; private $connection_correct = false; public function __construct($server, $user = "anonymous", $password = "[email protected]") { $this->server = $server; $this->user = $user; $this->password = $password; $this->connection_id = ftp_connect($this->server); $this->connection_correct = ftp_login($this->connection_id, $this->user, $this->password); if ( (!$this->connection_id) || (!$this->connection_correct) ){ echo "Error! Couldn't connect to $this->server"; var_dump($this->connection_id); var_dump($this->connection_correct); return false; } else { echo "Successfully connected to $this->server, user: $this->user"; $this->connection_correct = true; return true; } } } I reckon that body of the class is insignificant at the moment. Main issue is that I have some problems with understanding OOP idea. I wanted to add sending emails every time, when the code is run. I have downloaded PHPMailer Class and extended my class with it: class ftpConnect extends PHPMailer {...} I have added some variables and methods and everything works as expected to that point. I thought: why not to add storing everything in database. Everytime user runs above code, proper information should be stored in database. I could edit my ftpConnect class and add database connecting to the constructor, and some other methods to updating tables. But database connecting and all that stuff could be used by other classes in the future, so it definitely should be implemented in seperate class. But my "main" ftpConnect class already extends one class and could not extend not a single one more. I have no idea how can I resolve this problem. Maybe my ftpConnect class is to complex and I should somehow divide it into couple smaller classes? Any help is much appreciated.

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  • Have main thread wait for a boost thread complete a task (but not finish).

    - by JAKE6459
    I have found plenty on making one thread wait for another to finish executing before continuing, but that is not what I wanted to do. I am not very familiar with using any multi-threading apis but right now I'm trying to learn boost. My situation is that I am using my main thread (the starting one from int main()) to create an instance of a class that is in charge of interacting with the main GUI. A class function is then called that creates a boost thread which in turn creates the GUI and runs the message pump. The thing I want to do is when my main thread calls the classes member function to create the GUI, I don't want that function to return until I tell it to from the newly created thread. This way my main thread can't continue and call more functions from the GUI class that interact with the GUI thread until that thread has completed GUI creation and entered the message loop. I think I may be able to figure it out if it was multiple boost thread objects interacting with each other, but when it is the main thread (non-boost object) interacting with a boost thread object, I get lost. Eventually I want a loop in my main thread to call a class function (among other tasks) to check if the user as entered any new input into the GUI (buy any changes detected by the message loop being updated into a struct and changing a bool to tell the main thread in the class function a change has occurred). Any suggestions for any of this would be greatly appreciated. This is the member function called by the main thread. int ANNGUI::CreateGUI() { GUIMain = new Main(); GUIThread = new boost::thread(boost::bind(&Main::MainThreadFunc, GUIMain)); return 0; }; This is the boost thread starting function. void Main::MainThreadFunc() { ANNVariables = new GUIVariables; WndProc = new WindowProcedure; ANNWindowsClass = new WindowsClass(ANNVariables, WndProc); ANNWindow = new MainWindow(ANNVariables); GUIMessagePump = new MessagePump; ANNWindow-ShowWindows(); while(true) { GUIMessagePump-ProcessMessage(); } }; BTW, everything compiles fine and when I run it, it works I just put a sleep() in the main thread so I can play with the GUI a little.

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  • C# Different class objects in one list

    - by jeah_wicer
    I have looked around some now to find a solution to this problem. I found several ways that could solve it but to be honest I didn't realize which of the ways that would be considered the "right" C# or OOP way of solving it. My goal is not only to solve the problems but also to develop a good set of code standards and I'm fairly sure there's a standard way to handle this problem. Let's say I have 2 types of printer hardwares with their respective classes and ways of communicating: PrinterType1, PrinterType2. I would also like to be able to later on add another type if neccessary. One step up in abstraction those have much in common. It should be possible to send a string to each one of them as an example. They both have variables in common and variables unique to each class. (One for instance communicates via COM-port and has such an object, while the other one communicates via TCP and has such an object). I would however like to just implement a List of all those printers and be able to go through the list and perform things as "Send(string message)" on all Printers regardless of type. I would also like to access variables like "PrinterList[0].Name" that are the same for both objects, however I would also at some places like to access data that is specific to the object itself (For instance in the settings window of the application where the COM-port name is set for one object and the IP/port number for another). So, in short something like: In common: Name Send() Specific to PrinterType1: Port Specific to PrinterType2: IP And I wish to, for instance, do Send() on all objects regardless of type and the number of objects present. I've read about polymorphism, Generics, interfaces and such, but I would like to know how this, in my eyes basic, problem typically would be dealt with in C# (and/or OOP in general). I actually did try to make a base class, but it didn't quite seem right to me. For instance I have no use of a "string Send(string Message)" function in the base class itself. So why would I define one there that needs to be overridden in the derived classes when I would never use the function in the base class ever in the first place? I'm really thankful for any answers. People around here seem very knowledgeable and this place has provided me with many solutions earlier. Now I finally have an account to answer and vote with too. EDIT: To additionally explain, I would also like to be able to access the objects of the actual printertype. For instance the Port variable in PrinterType1 which is a SerialPort object. I would like to access it like: PrinterList[0].Port.Open() and have access to the full range of functionality of the underlaying port. At the same time I would like to call generic functions that work in the same way for the different objects (but with different implementations): foreach (printer in Printers) printer.Send(message)

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  • how to list out the submited data in same page where form submitted?

    - by OM The Eternity
    I have a form with 3 text values and one image.. I want to save these values such that i can display these records in the list below.. how can i do that... I am using osCommerce For example: <form method="post" id="fm-form" action ="" enctype="multipart/form-data"> <label>Name:</label> <input type="text" id="fm-name" name="fm-name" value="" /> <label>Email:</label> <input type="text" id="fm-email" name="fm-email" value="" /> <label>Birthdate:</label> <input type="text" id="fm-birthdate" name="fm-birthdate" value="" /> <input type="file" id="fm-image" name="fm-image"/> <input type="submit" id="fm-submit" value="Save it"> </form> <table width="100%" border="0" cellspacing="0" cellpadding="0"> <tr > <td align="center" class="productListing-heading">Product(s)</td> <td align="center" class="productListing-heading">Edit</td> <td align="center" class="productListing-heading">Delete</td> </tr> <?php for($i=0;$i<$count_image;$i++){?> <tr> <td align="left" class="productListing-data1"> <?php echo tep_image(DIR_WS_IMAGES . $file_realname, $save_image[$i], '110', '110');?> </td> <td align="center" class="productListing-data1">Edit</td> <td align="center" class="productListing-data1">Delete</td> </tr> <tr><td>&nbsp;</td></tr> <?php }?> </table> In the above format as the form is submitted the image has to be stored in a count_image array variable... and the on its count, the list below the form is displayed.. but i cannot get it worked.. could u pls help in doing this...

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  • Different data for different dates

    - by nsw1475
    I am making a web page which will allow users to input and view data for different dates, and to change the date, there are two buttons, one of which will display the previous day, and one which will show the next day. I know that I can do this by submitting forms and reloading the page every time they press one of these buttons, but I would rather use javascript and not have to submit a form, but I am having troubles getting it to work. Currently, I have the two buttons, and the date stored in a PHP variable, as shown in my code below: <script> function init() { <? $nutrDate = $this->parseDate(date('m/d/Y')); ?> } function nutrPrevDay() { <? $nutrDate = mktime(0, 0, 0, date('m',$nutrDate), date('d',$nutrDate)-1, date('Y',$nutrDate)); ?> alert("<? echo(date("m/d/y", $nutrDate)) ?>"); } function nutrNextDay() { <? $nutrDate = mktime(0, 0, 0, date('m',$nutrDate), date('d',$nutrDate)+1, date('Y',$nutrDate)); ?> } window.onload = init; </script> <p style="text-align:center; font-size:14px; color:#03F"> <button onclick="nutrPrevDay()" style="width:200px" >< Show Previous Day</button> <? echo(date('m/d/Y', $nutrDate)) ?> <button onclick="nutrNextDay()" style="width:200px">Show Next Day ></button> </p> I have the alert in the nutrPrevDay() only as debugging. What happens is when I click on the button, the alert shows that the day is correctly decreased (for example from May 17 to May 16), but only decreases one day, and not one day for every click. Also, I do not know how to make the text on the page (created by the line ) change to display the new date after a button is clicked. So here are my questions: 1) Is it possible to dynamically change data (such as text, and in the future, SQL queries) on a page using javascript without having to reload a page when clicking on a button? 2) If possible, how can I make those changes? 3) How can I fix this so that it will increment and decrement through dates every time a button is clicked?

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  • Joining the same model twice in a clean way, but making the code reusable

    - by Shako
    I have a model Painting which has a Paintingtitle in each language and a Paintingdescription in each language: class Painting < ActiveRecord::Base has_many :paintingtitles, :dependent => :destroy has_many :paintingdescriptions, :dependent => :destroy end class Paintingtitle < ActiveRecord::Base belongs_to :painting belongs_to :language end class Paintingdescription < ActiveRecord::Base belongs_to :painting belongs_to :language end class Language < ActiveRecord::Base has_many :paintingtitles, :dependent => :nullify has_many :paintingdescriptions, :dependent => :nullify has_many :paintings, :through => :paintingtitles end As you might notice, I reference the Language model from my Painting model via both the Paintingtitle model and Paintingdescription model. This works for me when getting a list of paintings with their title and description in a specific language: cond = {"paintingdescription_languages.code" => language_code, "paintingtitle_languages.code" => language_code} cond['paintings.publish'] = 1 unless admin paginate( :all, :select => ["paintings.id, paintings.publish, paintings.photo_file_name, paintingtitles.title, paintingdescriptions.description"], :joins => " INNER JOIN paintingdescriptions ON (paintings.id = paintingdescriptions.painting_id) INNER JOIN paintingtitles ON (paintings.id = paintingtitles.painting_id) INNER JOIN languages paintingdescription_languages ON (paintingdescription_languages.id = paintingdescriptions.language_id) INNER JOIN languages paintingtitle_languages ON (paintingtitle_languages.id = paintingtitles.language_id) ", :conditions => cond, :page => page, :per_page => APP_CONFIG['per_page'], :order => "id DESC" ) Now I wonder if this is a correct way of doing this. I need to fetch paintings with their title and description in different functions, but I don't want to specify this long join statement each time. Is there a cleaner way, for instance making use of the has_many through? e.g. has_many :paintingdescription_languages, :through => :paintingdescriptions, :source => :language has_many :paintingtitle_languages, :through => :paintingtitles, :source => :language But if I implement above 2 lines together with the following ones, then only paintingtitles are filtered by language, and not the paintingdescriptions: cond = {"languages.code" => language_code} cond['paintings.publish'] = 1 unless admin paginate( :all, :select => ["paintings.id, paintings.publish, paintings.photo_file_name, paintingtitles.title, paintingdescriptions.description"], :joins => [:paintingdescription_languages, :paintingtitle_languages], :conditions => cond, :page => page, :per_page => APP_CONFIG['per_page'], :order => "id DESC" )

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