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  • Overloading the QDataStream << and >> operators for a user-defined type

    - by Alex Wood
    I have a an object I'd like to be able to read and write to/from a QDataStream. The header is as follows: class Compound { public: Compound(QString, QPixmap*, Ui::MainWindow*); void saveCurrentInfo(); void restoreSavedInfo(QGraphicsScene*); void setImage(QPixmap*); QString getName(); private: QString name, homeNotes, addNotes, expText; Ui::MainWindow *gui; QPixmap *image; struct NMRdata { QString hnmrText, cnmrText, hn_nmrText, hn_nmrNucl, notes; int hnmrFreqIndex, cnmrFreqIndex, hn_nmrFreqIndex, hnmrSolvIndex, cnmrSolvIndex, hn_nmrSolvIndex; }*nmr_data; struct IRdata { QString uvConc, lowResMethod, irText, uvText, lowResText, highResText, highResCalc, highResFnd, highResFrmla, notes; int irSolvIndex, uvSolvIndex; }*ir_data; struct PhysicalData { QString mpEdit, bpEdit, mpParensEdit, bpParensEdit, rfEdit, phyText, optAlpha, optConc, elemText, elemFrmla, notes; int phySolvIndex, optSolvIndex; }*physical_data; }; For all intensive purposes, the class just serves as an abstraction for a handful of QStrings and a QPixmap. Ideally, I would be able to write a QList to a QDataStream but I'm not exactly sure how to go about doing this. If operator overloading is a suitable solution, would writing code like friend QDataStream& operator << (QDataStream&,Compound) { ... } be a potential solution? I'm very open to suggestions! Please let me know if any further clarification is needed.

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  • Declaring functors for comparison ??

    - by Mr.Gando
    Hello, I have seen other people questions but found none that applied to what I'm trying to achieve here. I'm trying to sort Entities via my EntityManager class using std::sort and a std::vector<Entity *> /*Entity.h*/ class Entity { public: float x,y; }; struct compareByX{ bool operator()(const GameEntity &a, const GameEntity &b) { return (a.x < b.x); } }; /*Class EntityManager that uses Entitiy*/ typedef std::vector<Entity *> ENTITY_VECTOR; //Entity reference vector class EntityManager: public Entity { private: ENTITY_VECTOR managedEntities; public: void sortEntitiesX(); }; void EntityManager::sortEntitiesX() { /*perform sorting of the entitiesList by their X value*/ compareByX comparer; std::sort(entityList.begin(), entityList.end(), comparer); } I'm getting a dozen of errors like : error: no match for call to '(compareByX) (GameEntity* const&, GameEntity* const&)' : note: candidates are: bool compareByX::operator()(const GameEntity&, const GameEntity&) I'm not sure but ENTITY_VECTOR is std::vector<Entity *> , and I don't know if that could be the problem when using the compareByX functor ? I'm pretty new to C++, so any kind of help is welcome.

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  • Reference-type conversion operators: asking for trouble?

    - by Ben
    When I compile the following code using g++ class A {}; void foo(A&) {} int main() { foo(A()); return 0; } I get the following error messages: > g++ test.cpp -o test test.cpp: In function ‘int main()’: test.cpp:10: error: invalid initialization of non-const reference of type ‘A&’ from a temporary of type ‘A’ test.cpp:6: error: in passing argument 1 of ‘void foo(A&)’ After some reflection, these errors make plenty of sense to me. A() is just a temporary value, not an assignable location on the stack, so it wouldn't seem to have an address. If it doesn't have an address, then I can't hold a reference to it. Okay, fine. But wait! If I add the following conversion operator to the class A class A { public: operator A&() { return *this; } }; then all is well! My question is whether this even remotely safe. What exactly does this point to when A() is constructed as a temporary value? I am given some confidence by the fact that void foo(const A&) {} can accept temporary values according to g++ and all other compilers I've used. The const keyword can always be cast away, so it would surprise me if there were any actual semantic differences between a const A& parameter and an A& parameter. So I guess that's another way of asking my question: why is a const reference to a temporary value considered safe by the compiler whereas a non-const reference is not?

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  • Understanding evaluation of expressions containing '++' and '->' operators in C.

    - by Leif Ericson
    Consider this example: struct { int num; } s, *ps; s.num = 0; ps = &s; ++ps->num; printf("%d", s.num); /* Prints 1 */ It prints 1. So I understand that it is because according to operators precedence, -> is higher than ++, so the value ps->num (which is 0) is firstly fetched and then the ++ operator operates on it, so it increments it to 1. struct { int num; } s, *ps; s.num = 0; ps = &s; ps++->num; printf("%d", s.num); /* Prints 0 */ In this example I get 0 and I don't understand why; the explanation of the first example should be the same for this example. But it seems that this expression is evaluated as follows: At first, the operator ++ operates, and it operates on ps, so it increments it to the next struct. Only then -> operates and it does nothing because it just fetches the num field of the next struct and does nothing with it. But it contradicts the precedence of operators, which says that -> have higher precedence than ++. Can someone explain this behavior? Edit: After reading two answers which refer to a C++ precedence tables which indicate that a prefix ++/-- operators have lower precedence than ->, I did some googling and came up with this link that states that this rule applies also to C itself. It fits exactly and fully explains this behavior, but I must add that the table in this link contradicts a table in my own copy of K&R ANSI C. So if you have suggestions as to which source is correct I would like to know. Thanks.

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  • Swig C++ Lua Pass class by reference

    - by Jeremy
    I don't know why I'm having a hard time with this. All I want to do is this: class foo { public: foo(){} ~foo(){} float a,b; }; class foo2 { public: foo2(){} foo2(const foo &f){*this = f;} ~foo2(){} void operator=(const foo& f){ x = f.a; y = f.b; } float x,y; }; /* Usage(cpp): foo f; foo2 f2(f); //or using the = operator f2 = f; */ The problem I'm having is that, after swigging this code, I can't figure out how to make the lua script play nice. /* Usage(lua) f = example.foo() f2 = example.foo2(f) --error */ The error I get is "Wrong arguments for overloaded function 'new_Foo2'": Possible c/c++ prototypes are: foo2() foo2(foo const &) The same thing happens if I try and use do f2 = f. As I understand it everything is stored as a pointer so I did try adding an additional constructor that took a pointer to foo but to no avail.

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  • Automatically converting an A* into a B*

    - by Xavier Nodet
    Hi, Suppose I'm given a class A. I would like to wrap pointers to it into a small class B, some kind of smart pointer, with the constraint that a B* is automatically converted to an A* so that I don't need to rewrite the code that already uses A*. I would therefore want to modify B so that the following compiles... struct A { void foo() {} }; template <class K> struct B { B(K* k) : _k(k) {} //operator K*() {return _k;} //K* operator->() {return _k;} private: K* _k; }; void doSomething(A*) {} void test() { A a; A* pointer_to_a (&a); B<A> b (pointer_to_a); //b->foo(); // I don't need those two... //doSomething(b); B<A>* pointer_to_b (&b); pointer_to_b->foo(); // 'foo' : is not a member of 'B<K>' doSomething(pointer_to_b); // 'doSomething' : cannot convert parameter 1 from 'B<K> *' to 'A *' } Note that B inheriting from A is not an option (instances of A are created in factories out of my control)... Is it possible? Thanks.

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  • Make conversion to a native type explicit in C++

    - by Tal Pressman
    I'm trying to write a class that implements 64-bit ints for a compiler that doesn't support long long, to be used in existing code. Basically, I should be able to have a typedef somewhere that selects whether I want to use long long or my class, and everything else should compile and work. So, I obviously need conversion constructors from int, long, etc., and the respective conversion operators (casts) to those types. This seems to cause errors with arithmetic operators. With native types, the compiler "knows" that when operator*(int, char) is called, it should promote the char to int and call operator*(int, int) (rather than casting the int to char, for example). In my case it gets confused between the various built-in operators and the ones I created. It seems to me like if I could flag the conversion operators as explicit somehow, that it would solve the issue, but as far as I can tell the explicit keyword is only for constructors (and I can't make constructors for built-in types). So is there any way of marking the casts as explicit? Or am I barking up the wrong tree here and there's another way of solving this? Or maybe I'm just doing something else wrong...

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  • Is it possible to implement events in C++?

    - by acidzombie24
    I wanted to implement a C# event in C++ just to see if i could do it. I got stuck, i know the bottom is wrong but what i realize my biggest problem is... How do i overload the () operator to be whatever is in T in this case int func(float)? I cant? can i? Can i implement a good alternative? #include <deque> using namespace std; typedef int(*MyFunc)(float); template<class T> class MyEvent { deque<T> ls; public: MyEvent& operator +=(T t) { ls.push_back(t); return *this; } }; static int test(float f){return (int)f; } int main(){ MyEvent<MyFunc> e; e += test; }

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  • What does the `new` keyword do

    - by Mike
    I'm following a Java tutorial online, trying to learn the language, and it's bouncing between two semantics for using arrays. long results[] = new long[3]; results[0] = 1; results[1] = 2; results[2] = 3; and: long results[] = {1, 2, 3}; The tutorial never really mentioned why it switched back and forth between the two so I searched a little on the topic. My current understanding is that the new operator is creating an object of "array of longs" type. What I do not understand is why do I want that, and what are the ramifications of that? Are there certain "array" specific methods that won't work on an array unless it's an "array object"? Is there anything that I can't do with an "array object" that I can do with a normal array? Does the Java VM have to do clean up on objects initialized with the new operator that it wouldn't normally have to do? I'm coming from C, so my Java terminology, may not be correct here, so please ask for clarification if something's not understandable.

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  • Extract news links from news website

    - by Ali
    Is there any reliable method to find out the collection of links which is directed us to detail news page. in other word after visiting the first page of website I just want those links that refer to a news item. any solution ?

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  • Get the rendered text from HTML (Delphi)

    - by Daisetsu
    I have some HTML and I need to extract the actual written text from the page. So far I have tried using a web browser and rendering the page, then going to the document property and grabbing the text. This works, but only where the browser is supported (IE com object). The problem is I want this to be able to run under wine also, so I need a solution that doesn't use IE COM. There must be a programatic way to do this that is reasonable.

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  • Getting BeautifulSoup to find a specific <p>

    - by Ryan
    I'm trying to put together a basic HTML scraper for a variety of scientific journal websites, specifically trying to get the abstract or introductory paragraph. The current journal I'm working on is Nature, and the article I've been using as my sample can be seen at http://www.nature.com/nature/journal/v463/n7284/abs/nature08715.html. I can't get the abstract out of that page, however. I'm searching for everything between the <p class="lead">...</p> tags, but I can't seem to figure out how to isolate them. I thought it would be something simple like from BeautifulSoup import BeautifulSoup import re import urllib2 address="http://www.nature.com/nature/journal/v463/n7284/full/nature08715.html" html = urllib2.urlopen(address).read() soup = BeautifulSoup(html) abstract = soup.find('p', attrs={'class' : 'lead'}) print abstract Using Python 2.5, BeautifulSoup 3.0.8, running this returns 'None'. I have no option of using anything else that needs to be compiled/installed (like lxml). Is BeautifulSoup confused, or am I?

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  • How do you parse an HTML in vb.net

    - by tooleb
    I would like to know if there is a simple way to parse HTML in vb.net. I know that HTML is not sctrict subset of XML, but it would be nice if it could be treated that way. Is there anything out there that would let me parse HTML in an XML-like way in VB.net?

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  • need help working with the Jericho Html Parser

    - by rookie
    Hi all I've simply used the following program on the url below http://jericho.htmlparser.net/samples/console/src/ExtractText.java My goal is to be able to extract the main body text, to be able to summarize it and present the summarized text as output to the user. My problem is that, I'm not sure how I'd modify the above program to only get the required text from the webpage, without the links or any other information. Again, I'd really appreciate any help I could get. Thanks in advance

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  • Extracting information from PDFs of research papers

    - by Christopher Gutteridge
    I need a mechanism for extracting bibliographic metadata from PDF documents, to save people entering it by hand or cut-and-pasting it. At the very least, the title and abstract. The list of authors and their affiliations would be good. Extracting out the references would be amazing. Ideally this would be an open source solution. The problem is that not all PDF's encode the text, and many which do fail to preserve the logical order of the text, so just doing pdf2text gives you line 1 of column 1, line 1 of column 2, line 2 of column 1 etc. I know there's a lot of libraries. It's identifying the abstract, title authors etc. on the document that I need to solve. This is never going to be possible every time, but 80% would save a lot of human effort.

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  • parsing HTML on the iPhone

    - by Ben Alpert
    Can anyone recommend a C or Objective-C library for HTML parsing? It needs to handle messy HTML code that won't quite validate. Does such a library exist, or am I better off just trying to use regular expressions?

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  • How to extract data from a PDF?

    - by Fermin
    Hi, My company receives data from an external company via Excel. We export this into SQL Server to run reports on the data. They are now changing to PDF format, is there a way to reliably port the data from the PDF and insert it into our SQL Server 2008 database? Would this require writing an app or is there an automated way of doing this?

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  • How do I extract HTML content using Regex in PHP

    - by gAMBOOKa
    I know, i know... regex is not the best way to extract HTML text. But I need to extract article text from a lot of pages, I can store regexes in the database for each website. I'm not sure how XML parsers would work with multiple websites. You'd need a separate function for each website. In any case, I don't know much about regexes, so bear with me. I've got an HTML page in a format similar to this <html> <head>...</head> <body> <div class=nav>...</div><p id="someshit" /> <div class=body>....</div> <div class=footer>...</div> </body> I need to extract the contents of the body class container. I tried this. $pattern = "/<div class=\"body\">\(.*?\)<\/div>/sui" $text = $htmlPageAsIs; if (preg_match($pattern, $text, $matches)) echo "MATCHED!"; else echo "Sorry gambooka, but your text is in another castle."; What am I doing wrong? My text ends up in another castle.

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  • Extracting Window Contents

    - by user293392
    I need to extract window content if this is based on text, or at least the file path associated to that window. To-date, I have considered: 1. win32api 2. 3rd party libraries 3. wrapper classes However, I am not satisfied with the solutions. So any ideas how this can be done in a clean way?

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  • Extract part of a git repository?

    - by Riobard
    Assume my git repository has the following structure: /.git /Project /Project/SubProject-0 /Project/SubProject-1 /Project/SubProject-2 and the repository has quite some commits. Now one of the subprojects (SubProject-0) grows pretty big, and I want to take SubProject-0 out and set it up as a standalone project. Is it possible to extract all the commit history involving SubProject-0 from the parent git repository and move it to a new one?

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  • Access Adobe InDesign files

    - by PeterMmm
    I need some directions for the following problem: I have a lot of InDesign files and i have to setup a process that will track if a certain paragraph or text block has changed between diferent versions of the file. If the text block has changed i want to extract that text block in a "portable" format (html, pdf, txt). Is there an Adobe product that would do that ? Is there any public API to access an InDesign file ? Is there the posibility to export InDesign to, say, html ?

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  • Is there anything for Python that is like readability.js?

    - by Emre Sevinç
    Hi, I'm looking for a package / module / function etc. that is approximately the Python equivalent of Arc90's readability.js http://lab.arc90.com/experiments/readability http://lab.arc90.com/experiments/readability/js/readability.js so that I can give it some input.html and the result is cleaned up version of that html page's "main text". I want this so that I can use it on the server-side (unlike the JS version that runs only on browser side). Any ideas? PS: I have tried Rhino + env.js and that combination works but the performance is unacceptable it takes minutes to clean up most of the html content :( (still couldn't find why there is such a big performance difference).

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