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  • passing a class method as opposed to a function in std::sort

    - by memC
    hi, Within a class, I am trying to sort a vector, by passing a method of the same class. But it gives errors at the time of compilation. Can anyone tell what the problem is? Thank you! it gives the following error: argument of type bool (Sorter::)(D&, D&)' does not matchbool (Sorter::*)(D&, D&)' I have also tried using sortBynumber(D const& d1, D const& d2) #include<vector> #include<stdio.h> #include<iostream> #include<algorithm> class D { public: int getNumber(); D(int val); ~D(){}; private: int num; }; D::D(int val){ num = val; }; int D::getNumber(){ return num; }; class Sorter { public: void doSorting(); bool sortByNumber(D& d1, D& d2); std::vector<D> vec_D; Sorter(); ~Sorter(){}; private: int num; }; Sorter::Sorter(){ int i; for ( i = 0; i < 10; i++){ vec_D.push_back(D(i)); } }; bool Sorter::sortByNumber(D& d1, D& d2){ return d1.getNumber() < d2.getNumber(); }; void Sorter::doSorting(){ std::sort(vec_D.begin(), vec_D.end(), this->sortByNumber); }; int main(){ Sorter s; s.doSorting(); std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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  • foo and _foo - about variables inside a class

    - by kame
    class ClassName(object): """ """ def __init__(self, foo, bar): """ """ self.foo = foo # read-write property self.bar = bar # simple attribute def _set_foo(self, value): self._foo = value def _get_foo(self): return self._foo foo = property(_get_foo, _set_foo) a = ClassName(1,2) #a._set_foo(3) print a._get_foo() When I print a._get_foo() the function _get_foo prints the variable self._foo . But where does it come from? self._foo and self.foo are different, aren't they?

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  • What's the Difference Between These Two Ruby Class Initialization Definitions?

    - by michaelmichael
    I'm working through a book on Ruby, and the author used a slightly different form for writing a class initialization definition than he has in previous sections of the book. It looks like this: class Ticket attr_accessor :venue, :date def initialize(venue, date) self.venue = venue self.date = date end end In previous sections of the book, it would've been defined like this: class Ticket attr_accessor :venue, :date def initialize(venue, date) @venue = venue @date = date end end Is there any functional difference between using the setter method, as in the first example, vs. using the instance variable as in the second? They both seem to work. Even mixing them up works: class Ticket attr_accessor :venue, :date def initialize(venue, date) @venue = venue self.date = date end end

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  • Java newbie problem: classes of the same package accessing one another?

    - by HH
    Test.java and SetWord.java belong to the package tools. Test.java needs to access SetWord but an odd error 'cannot find' SetWord appear. The package limits the visibility, it works without 'package tools;' lines. How can I acess the SetWords with Test in the same pkg? In general, how can classes access one another in the same pkg? Test.java package tools; import java.io.*; import java.util.*; public class Test{ public static void main(String[] args) { //IT CANNOT FIND SetWords despite the same folder, why? SetWord sw=new SetWord(); System.out.println(st.set("HELLO)"); } } SetWord.java package tools; import java.io.*; import java.util.*; public class SetWord{ public SetWord(){} public String set(String s) { return s.trim().toLowerCase(); } }

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  • Codeigniter: simple form function

    - by Kevin Brown
    I'm stuck writing a simple form...I feel dumb. Here's my controller: function welcome_message(){ //Update welcome message $id = $this->session->userdata('id'); $profile['welcome_message'] = $this->input->post('welcome_message'); $this->db->update('be_user_profiles',$profile, array('user_id' => $id)); } And the html: <?php print form_open('home/welcome_message')?> <input type="checkbox" value="0" checked="false">Don't show me this again</input> <p> <input class="button submit" type="submit" class="close-box" value="Close" /> </p> <?php print form_close()?> Edit I simply need it to submit to a private function and return to the home page (page submitted from).

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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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  • Unable to open images with Python's Image.open()

    - by ensnare
    My code reads: import Image def generateThumbnail(self, width, height): """ Generates thumbnails for an image """ im = Image.open(self._file) When I call this function, I get an error: ? AttributeError: type object 'Image' has no attribute 'open' However in the console: import Image im = Image.open('test.jpg') I have no problem. Any ideas? Thanks!

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  • c++ meaning of the use of const in the signature

    - by jbu
    Please help me understand the following signature: err_type funcName(const Type& buffer) const; so for the first const, does that mean the contents of Type cannot change or that the reference cannot change? secondly, what does the second const mean? I don't really even have a hint. Thanks in advance, jbu

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  • JButtons re-enable themselves after being disabled

    - by Anarchist
    I have an array of JButtons which form a keypad interface. After six numbers are entered I want to disable the keypad so that no further numbers can be entered by the user. I have written the code and the buttons do disable until the mouse hovers above any of them, then the buttons seem to re-enable themselves and run actionEvents added to them. The full code is available here. Possible things that I think are wrong. There is some sort of MouseListener which is ignoring when I set button.setEnabled(false); I haven't separated attributes from the buildGUI(); correctly, I only did this anyway so that the inner class could access them. Possibly something to do with the gridLayout as disabling the buttons seems to work for my services JPanel buttons.

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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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  • TB3.0.10: Messages being sent back to me

    - by punkinette64
    Hello, I don't know if this will make any sense to you; but here goes. When I send an email and I get a response, more often than not, in the 'to:' is my email address. However, my email address also ends up in the 'from' column.The 'reply-from' address is nowhere to be found;so I don't have any address with which I can send my reply, as both of them have just my email address. What am I doing wrong here? Is there some set-up in my TOOLOPTIONS set-up incorrectly? The set-up in OPTIONS is pretty difficult to understand and it doesn't offer any 'to' or 'reply-from' choices. This is critical because I just cannot answer my emails because there is no one I can send a reply to. Please, please try to help me. If you have the answer, please email me at: [email protected] Thank you. Blessings. Shiloh

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  • Why can't I access the instance.__class__ attribute in Python?

    - by froadie
    I'm new to Python, and I know I must be missing something pretty simple, but why doesn't this very, very simple code work? class myClass: pass testObject = myClass print testObject.__class__ I get the following error: AttributeError: class myClass has no attribute '__class__' Doesn't every object in Python have a __class__ attribute?

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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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  • C++ function-pointer and inheritance

    - by pingvinus
    In parent class I have function, that operates under an array of functions, declared in child-class, number of functions for every child-class may vary. But since every function uses some object-variables, I can't declare them as static. I've try to do something like this: class A { public: typedef int (A::*func)(); func * fs; void f() { /*call functions from this->fs*/ } }; class B : public A { public: int smth; B(int smth) { this->smth = smth; this->fs = new func[1]; fs[0] = &B::f; } int f() { return smth + 1; } }; But, obviously it doesn't work. Any suggestions?

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  • give feedback on this pointer program

    - by JohnWong
    This is relatively simple program. But I want to get some feedback about how I can improve this program (if any), for example, unnecessary statements? #include<iostream> #include<fstream> using namespace std; double Average(double*,int); int main() { ifstream inFile("data2.txt"); const int SIZE = 4; double *array = new double(SIZE); double *temp; temp = array; for (int i = 0; i < SIZE; i++) { inFile >> *array++; } cout << "Average is: " << Average(temp, SIZE) << endl; } double Average(double *pointer, int x) { double sum = 0; for (int i = 0; i < x; i++) { sum += *pointer++; } return (sum/x); } The codes are valid and the program is working fine. But I just want to hear what you guys think, since most of you have more experience than I do (well I am only a freshman ... lol) Thanks.

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  • 3D and AI basics. The foundation before the coding.

    - by Allan
    Hi, everyone. (If you have the time and patience:) I've recently made the decision to study programming seriously and I'm about to order TAOCP and Concrete Mathematics to begin my studies (please don't get caught up on this). I'm very much interested in learning and understanding how 3D works but I'm aware that if I plan to do it right there's still a long walk before I get to actually play with 3D coding. Now to the question.. (tl;dr) Excluding programming itself, what disciplines do I have to be familiar with to code 3D? What kinds of mathematics? Physics? What else? What books do you recommend on such subjects? Now read it all again but replacing "3D" with "AI". Please don't recommend computer-specific books. The question is about the foundation to be learned before using the machine. Also, if possible, please keep the list brief; I plan to order one book on each subject but no more than that for now. Excuse me for any English mistakes, it's not my first language. Thank you.

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  • What's the Difference Between These Two Ruby Class Initialaztion Definitions?

    - by michaelmichael
    I'm working through a book on Ruby, and the author used a slightly different form for writing a class initialization definition than he has in previous sections of the book. It looks like this: class Ticket attr_accessor :venue, :date def initialize(venue, date) self.venue = venue self.date = date end end In previous sections of the book, it would've been defined like this: class Ticket attr_accessor :venue, :date def initialize(venue, date) @venue = venue @date = date end end Is there any functional difference between using the setter method, as in the first example vs. using the instance variable in the second? They both seem to work. Even mixing them up seems to work: class Ticket attr_accessor :venue, :date def initialize(venue, date) @venue = venue self.date = date end end

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  • Definition of variables/fields type within a constructor, how is it done?

    - by elementz
    I just had a look at Suns Java tutorial, and found something that totally confused me: Given the following example: public Bicycle(int startCadence, int startSpeed, int startGear) { gear = startGear; cadence = startCadence; speed = startSpeed; } Why is it, that the types of the variables (fields?) gear, cadence and speed do not need to be defined? I would have written it as follows: public Bicycle(int startCadence, int startSpeed, int startGear) { int gear = startGear; int cadence = startCadence; int speed = startSpeed; } What would be the actual differnce?

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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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