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  • What are the books about Open-Source that everyone interested in should read?

    - by Edu Zamora
    Currently I am working and running my first Open-Source project and though I am quite happy how things are working so far, I have the feeling that a lot of things could be done better. So, what books about Open-Source would you recommend me in order to help filling this gap and making things better every day? What are the books that influenced you the most? I am especially interested in: - How to organize and run an Open-Source project - Best practices - Manage and involve users and developers - How to announce and do the releases - Legal issues

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  • Sort database entries via a dropdown list

    - by Lin
    Hello! I'm curious if anyone could possibly help me, because I can't find anything exactly related to it anywhere, and it's driving me nuts. I'd like to have a dropdown list on a page, that will give the visitor the option to sort all entries by year. I have entries from i.e. 2001, 2005, 2009, 2010. The years should be displayed in the dropdown, so the visitor can easily just select all entries dated 2001 if they want. The year for each entry is located in the one database table I have. In other words, I simply want a "sort by" dropdown that you can see on pretty much any shopping site nowadays. But with set years. Thanks in advance for any replies!

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  • Dynamically calling functions - Python

    - by RadiantHex
    Hi folks, I have a list of functions... e.g. def filter_bunnies(pets): ... def filter_turtles(pets): ... def filter_narwhals(pets): ... Is there a way to call these functions by using a string representing their name? e.g. 'filter_bunnies', 'filter_turtles', 'filter_narwhals'

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  • AWK: how to reuse a result NR-times without removing END?

    - by HH
    How can I get all differences, not just one? I want to use the calculated result for each item in the third column. The dilemma is that if I remove END I can print $3 but cannot have ave. If I leave END I have ave but not all differences. awk '{sum+=$3} END {ave=sum/NR} END {print $3-ave}' coriolis_data -0.00964 // I want to see the rest differences, how? coriolis_data .105 0.005 0.9766 0.0001 0.595 0.005 .095 0.005 0.9963 0.0001 0.595 0.005 .115 0.005 0.9687 0.0001 0.595 0.005 .105 0.005 0.9693 0.0001 0.595 0.005 .095 0.005 0.9798 0.0001 0.595 0.005 .105 0.005 0.9798 0.0001 0.595 0.005 .095 0.005 0.9711 0.0001 0.595 0.005 .110 0.005 0.9640 0.0001 0.595 0.005 .105 0.005 0.9704 0.0001 0.595 0.005 .090 0.005 0.9644 0.0001 0.595 0.005

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  • Performance hit from C++ style casts?

    - by Trevor Boyd Smith
    I am new to C++ style casts and I am worried that using C++ style casts will ruin the performance of my application because I have a real-time-critical deadline in my interrupt-service-routine. I heard that some casts will even throw exceptions! I would like to use the C++ style casts because it would make my code more "robust". However, if there is any performance hit then I will probably not use C++ style casts and will instead spend more time testing the code that uses C-style casts. Has anyone done any rigorous testing/profiling to compare the performance of C++ style casts to C style casts? What were your results? What conclusions did you draw?

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  • array, I/O file and standard deviation (c++)

    - by JohnWong
    double s_deviation(double data[],int cnt, double mean) { int i; double sum= 0; double sdeviation; double x; //x = mean(billy,a_size); for(i=0; i<cnt; i++) { sum += ((data[i]) - (mean)); } sdeviation = sqrt(sum/((double)cnt)); return sdeviation; } When I cout the result from this function, it gave me NaN. I tested the value of (mean) and data[i] using return data[i] and return mean they are valid. when i replaced mean with an actual number, the operation returned a finite number. but with mean as a variable, it produced NaH. I can't see anything wrong with my code at the moment. Again, I am sure mean, data are getting the right number based on those tests. Thank you

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  • Array of function pointers in Java

    - by Waltzy
    I have read this question and I'm still not sure whether it is possible to keep pointers to methods in an array in Java, if anyone knows if this is possible or not it would be a real help. I'm trying to find an elegant solution of keeping a list of Strings and associated functions without writing a mess of hundreds of 'if's. Cheers edit- 'functions' changed to 'methods', seems to bug people.

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  • Java Graphics not displaying on successive function calls, why?

    - by primehunter326
    Hi, I'm making a visualization for a BST implementation (I posted another question about it the other day). I've created a GUI which displays the viewing area and buttons. I've added code to the BST implementation to recursively traverse the tree, the function takes in coordinates along with the Graphics object which are initially passed in by the main GUI class. My idea was that I'd just have this function re-draw the tree after every update (add, delete, etc...), drawing a rectangle over everything first to "refresh" the viewing area. This also means I could alter the BST implementation (i.e by adding a balance operation) and it wouldn't affect the visualization. The issue I'm having is that the draw function only works the first time it is called, after that it doesn't display anything. I guess I don't fully understand how the Graphics object works since it doesn't behave the way I'd expect it to when getting passed/called from different functions. I know the getGraphics function has something to do with it. Relevant code: private void draw(){ Graphics g = vPanel.getGraphics(); tree.drawTree(g,ORIGIN,ORIGIN); } vPanel is what I'm drawing on private void drawTree(Graphics g, BinaryNode<AnyType> n, int x, int y){ if( n != null ){ drawTree(g, n.left, x-10,y+10 ); if(n.selected){ g.setColor(Color.blue); } else{ g.setColor(Color.gray); } g.fillOval(x,y,20,20); g.setColor(Color.black); g.drawString(n.element.toString(),x,y); drawTree(g,n.right, x+10,y+10); } } It is passed the root node when it is called by the public function. Do I have to have: Graphics g = vPanel.getGraphics(); ...within the drawTree function? This doesn't make sense!! Thanks for your help.

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  • Beginning python for the web

    - by Josh K
    I'm looking for a nice tutorial or framework for developing Python written web applications. I've done lots in PHP, but very little in Python or Ruby and figured I'd start with the first one alphabetically.

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  • C++ Template problem adding two data types

    - by Sara
    I have a template class with an overloaded + operator. This is working fine when I am adding two ints or two doubles. How do I get it to add and int and a double and return the double? template <class T> class TemplateTest { private: T x; public: TemplateTest<T> operator+(const TemplateTest<T>& t1)const { return TemplateTest<T>(x + t1.x); } } in my main function i have void main() { TemplateTest intTt1 = TemplateTest<int>(2); TemplateTest intTt2 = TemplateTest<int>(4); TemplateTest doubleTt1 = TemplateTest<double>(2.1d); TemplateTest doubleTt2 = TemplateTest<double>(2.5d); std::cout << intTt1 + intTt2 << /n; std::cout << doubleTt1 + doubleTt2 << /n; } I want to be able to also do this std::cout << doubleTt1 + intTt2 << /n;

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  • C++: Trouble with templates (C2064)

    - by Rosarch
    I'm having compiler errors, and I'm not sure why. What am I doing wrong here: Hangman.cpp: set<char> Hangman::incorrectGuesses() { // Hangman line 103 return Utils::findAll_if<char>(guesses.begin(), guesses.end(), &Hangman::isIncorrectGuess); } bool Hangman::isIncorrectGuess(char c) { return correctAnswer.find(c) == string::npos; } Utils.h: namespace Utils { void PrintLine(const string& line, int tabLevel = 0); string getTabs(int tabLevel); template<class result_t, class Predicate> std::set<result_t> findAll_if(typename std::set<result_t>::iterator begin, typename std::set<result_t>::iterator end, Predicate pred) { std::set<result_t> result; // utils line 16 return detail::findAll_if_rec<result_t>(begin, end, pred, result); } } namespace detail { template<class result_t, class Predicate> std::set<result_t> findAll_if_rec(typename std::set<result_t>::iterator begin, typename std::set<result_t>::iterator end, Predicate pred, std::set<result_t> result) { // utils line 25 typename std::set<result_t>::iterator nextResultElem = find_if(begin, end, pred); if (nextResultElem == end) { return result; } result.insert(*nextResultElem); return findAll_if_rec(++nextResultElem, end, pred, result); } } This produces the following compiler errors: algorithm(83): error C2064: term does not evaluate to a function taking 1 arguments algorithm(95) : see reference to function template instantiation '_InIt std::_Find_if<std::_Tree_unchecked_const_iterator<_Mytree>,_Pr>(_InIt,_InIt,_Pr)' being compiled 1> with 1> [ 1> _InIt=std::_Tree_unchecked_const_iterator<std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>>, 1> _Mytree=std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>, 1> _Pr=bool (__thiscall Hangman::* )(char) 1> ] utils.h(25) : see reference to function template instantiation '_InIt std::find_if<std::_Tree_const_iterator<_Mytree>,Predicate>(_InIt,_InIt,_Pr)' being compiled 1> with 1> [ 1> _InIt=std::_Tree_const_iterator<std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>>, 1> _Mytree=std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>, 1> Predicate=bool (__thiscall Hangman::* )(char), 1> _Pr=bool (__thiscall Hangman::* )(char) 1> ] utils.h(16) : see reference to function template instantiation 'std::set<_Kty> detail::findAll_if_rec<result_t,Predicate>(std::_Tree_const_iterator<_Mytree>,std::_Tree_const_iterator<_Mytree>,Predicate,std::set<_Kty>)' being compiled 1> with 1> [ 1> _Kty=char, 1> result_t=char, 1> Predicate=bool (__thiscall Hangman::* )(char), 1> _Mytree=std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>> 1> ] hangman.cpp(103) : see reference to function template instantiation 'std::set<_Kty> Utils::findAll_if<char,bool(__thiscall Hangman::* )(char)>(std::_Tree_const_iterator<_Mytree>,std::_Tree_const_iterator<_Mytree>,Predicate)' being compiled 1> with 1> [ 1> _Kty=char, 1> _Mytree=std::_Tree_val<std::_Tset_traits<char,std::less<char>,std::allocator<char>,false>>, 1> Predicate=bool (__thiscall Hangman::* )(char) 1> ]

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  • Got a question I don't understand, can anyone make sense of it?

    - by user275074
    Question on a on-line resource paper: Create javascript so that the following methods produce the output listed next it. circle = new Circle(); console.log(circle.get_area()); // 3.141592653589793 circle.set_radius(10); console.log(circle.get_area()); // 314.1592653589793 console.log(circle); // the radius of my circle is 10 and it's area is 314.1592653589793 Can anyone understand what is being asked?

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  • C Array of string

    - by Meko
    HI. This is maybe simple question but I want to create two dimensional array and add it string like in java string str = "text" ; string [][] array = new [][] string ; array[i][j] = str ; But in C there is no string .I tried like this but here strcpy() gives error.It returns to assembly code. I am trying to read line by line from text and split line by space and add them to structure.But first I think that I must add each line and row in array and then making iteration and adding to structures fields. static const char filename[] = "student.txt"; FILE *file = fopen ( filename, "r" ); char line [ 128 ]; /* or other suitable maximum line size */ char delims [ ]=" "; char *result =NULL; char list[15]; char arra[128][128]; int i=0; int j=0; struct { char gruppa[10]; char familiya[20]; int uchaste; struct { int firsth; int second; int third; int fourht; int fifth; } exam; }student; for(i=0; i<128; i++) for(j=0; j<128; j++) arra[i][j] = '\0'; for(i=0; i<15; i++) list[i] = '\0'; if ( file != NULL ) { while ( fgets ( line, sizeof line, file ) != NULL ) { result = strtok(line,delims); while (result !=NULL) { strcpy(list,("%s",result)); strcpy(arra[i][j],list); // Here it gives errror j++; result = strtok(NULL,delims); } j=0; i++; } fclose ( file ); } else { perror ( filename ); } getchar(); return 0; }

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  • Using Python, How to copy files in 'temporary internet files' folder in Windows

    - by pythBegin
    I am using this code to find files recursively in a folder , with size greater than 50000 bytes. def listall(parent): lis=[] for root, dirs, files in os.walk(parent): for name in files: if os.path.getsize(os.path.join(root,name))>500000: lis.append(os.path.join(root,name)) return lis This is working fine. But when I used this on 'temporary internet files' folder in windows, am getting this error. Traceback (most recent call last): File "<pyshell#4>", line 1, in <module> listall(a) File "<pyshell#2>", line 5, in listall if os.path.getsize(os.path.join(root,name))>500000: File "C:\Python26\lib\genericpath.py", line 49, in getsize return os.stat(filename).st_size WindowsError: [Error 123] The filename, directory name, or volume label syntax is incorrect: 'C:\\Documents and Settings\\khedarnatha\\Local Settings\\Temporary Internet Files\\Content.IE5\\EDS8C2V7\\??????+1[1].jpg' I think this is because windows gives names with special characters in this specific folder... Please help to sort out this issue.

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  • Organising files and classes in XCode (iPhone application)

    - by pulegium
    It's a generic question and really a newbie one too, so bear with me... I'm playing with some iPhone development, and trying to create a simple "flip type" application. Nothing sophisticated, let's say on the flip side is a short application summary, bit like 'help' and on the main screen is a simple board game, let's say tic-tac-toe or similar. Now, XCode has generated me 'Main View', 'Flipside View' and 'Application Delegate' folders, with default template files in them. Now the question is where do I create appropriate 'MVC' classes? Let's say (V)iew classes are going to be the ones that have been automatically created. So the Flipside view class is responsible for generating text/images etc on the 'help' view. 'Main View' class is what draws the items on the table and updates the counters, etc. Where should I place the 'controller' class? And also, should it only be dealing with proxying only to the model? According to this the controller method is called from the view and manipulates the method classes. Similarly, the results from model are passed back to the view class by the controller issuing the calls to appropriate view methods. Similarly, where does the model class go? or should I just create a new folder for each, controller and model class files? What I'm after is the best practices, or just a short description how people normally structure their applications. I know it's very specific and also undefined... I came from Django background, so the way stuff is organised there is slightly different. Hope this makes sense, sorry if it's all bit vague, but I have to start somewhere :) And yes I've read quite few docs on the apple developer site, but trouble is that the documents are either going into too much detail about the language/framework/etc and the examples are way too simplistic. Actually, this leads me to the final question, has anyone know any good example of relatively complete application tutorial which I could use as a reference in organising my files?...

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  • I know the big picture but can't put it in place

    - by Simbilim
    Hi, I'm interested in web development and by that I mean the bigger projects like facebook or twitter. I know the basics of java, css, php and mysql. I know there is a lot more out there. I read about it. But I don't know what the purpose is and how to put in place. Things like: Scribe, thrift, casandra, Unix/Linux, shell/perl/python scripting, PostgreSQL, MongoDB, non-relational NoSQL datastores, JVM, nginx I want to know why they need it, how they use it and what te purpose is. What I need is a book like technical background of facebook for dummies or so. Are there any books or websites that explain this from scratch? Thank you!

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  • Setting the rank of a user-defined verb in J

    - by Gregory Higley
    Here's a function to calculate the digital sum of a number in J: digitalSum =: +/@:("."0)@": If I use b. to query the rank of this verb, I get _ 1 _, i.e., infinite. (We can ignore the dyadic case since digitalSum is not dyadic.) I would like the monadic rank of this verb to be 0, as reported by b.. The only way I know of to do this is to use a "shim", e.g., ds =: +/@:("."0)@": digitalSum =: ds"0 This works great, but I want to know whether it's the only way to do this, or if there's something else I'm missing.

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  • Why has to be size of dynamically-allocated array a static field?

    - by Ondrej Slinták
    I have a dummy class where I am testing arrays. I've noticed that when I want to dynamically allocate size of array at runtime, fields that indicate this size have to be static. I know I should probably use collections for this kind of code, but I'm more interested why do these fields have to be static? Is there any particular reason behind this? class Foo { private static int x; private static int y; private int[,] bar = new int[ x, y ]; public Foo( int a, int b ) { x = a; y = b; } }

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  • Java: Inputting text from a file using split

    - by 00PS
    I am inputting an adjacency list for a graph. There are three columns of data (vertex, destination, edge) separated by a single space. Here is my implementation so far: FileStream in = new FileStream("input1.txt"); Scanner s = new Scanner(in); String buffer; String [] line = null; while (s.hasNext()) { buffer = s.nextLine(); line = buffer.split("\\s+"); g.add(line[0]); System.out.println("Added vertex " + line[0] + "."); g.addEdge(line[0], line[1], Integer.parseInt(line[2])); System.out.println("Added edge from " + line[0] + " to " + line[1] + " with a weight of " + Integer.parseInt(line[2]) + "."); } System.out.println("Size of graph = " + g.size()); Here is the output: Added vertex a. Added edge from a to b with a weight of 9. Exception in thread "main" java.lang.NullPointerException at structure5.GraphListDirected.addEdge(GraphListDirected.java:93) at Driver.main(Driver.java:28) I was under the impression that line = buffer.split("\\s+"); would return a 2 dimensional array of Strings to the variable line. It seemed to work the first time but not the second. Any thoughts? I would also like some feedback on my implementation of this problem. Is there a better way? Anything to help out a novice! :)

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  • python: equivalent to Javascript "||" to override non-truthful value

    - by Jason S
    In Javascript I can do this: function A(x) { return x || 3; } This returns 3 if x is a "non-truthful" value like 0, null, false, and it returns x otherwise. This is useful for empty arguments, e.g. I can do A() and it will evaluate as 3. Does Python have an equivalent? I guess I could make one out of the ternary operator a if b else c but was wondering what people use for this.

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